Circulation in the Strait of Juan de Fuca some recent oceanographic observations

[From the U.S. Government Printing Office, www.gpo.gov]

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NOAA Technical Report ERL 399-PMEL 29

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Circulation in the Strait, of
Juan de Fuca

-4rEs
Some Recent Oceanographic
47 Observations

G. A. Cannor, Editor

June1978

QC
807.5
U66
no.399 U.S. DEPARTMENT OF COMMERCE
<

National Oceanic and Atmospheric Administration
Environmental Research Laboratories

COASTAL ZONE Y 1 '1983
INEORMATION CENTER
NOAA Technical Report ERL 399-PMEL 29

Circulation in the Strait of
9
0
Juan de Fuca
Some Recent oceanographic
E
O@
NT O@ Observations

G. A. Cannon, Editor
J. R. Holbrook and R. A. Feely, editorial assistants

Contributing Authors
Coastal Physics, PMEL
G. A. Cannon, R. L. Charnell, N. P. Laird, H. 0. Mofjeld, D. J. Pashinski, J. D. Schumacher

Chemistry and Biology, PMEL
E. T. Baker, D. M. Damkaer, R. A. Feely, J. D. Larrance

Deep Sea Physics, PMEL
D. Halpern, J. R. Holbrook

Numerical Studies, PMEL
J. A. Galt, J. Karpen, J. E. Overland, C. H. Pease, R. W. Stewart

Oceanographic Division, NOS
B. B. Parker
Remote Sensing Studies, PMEL ProPe"Y Of CSC Library
C. B. Sawyer

Pacific Marine Environmental Laboratory
Seattle, Washington
June1978 U . S . DEPARTMENT OF COMMERCE NOAA
COASTAL SERVICES CENTER
2234 SOUTH HOBSON AVENUE
CHARLESTON . SC 29405-2413

-0) U.S. DEPARTMENT OF COMMERCE
-25 cc Juanita M. Kreps, Secretary
il) If National Oceanic and Atmospheric Administration
Richard A. Frank, Administrator

Environmental Research Laboratories
Boulder, Colorado
Wilmot Hess, Director

NOTICE

Mention of a commercial company or product does not constitute an
endorsement by NOAA Environmental Research Labo@atories. Use
for publicity or advertising purposes of information from this publica-
tion concerning proprietary products or the tests of such products is
not authorized.

CONTENTS

Executive Summary ............................................... v
Abstract I
1. Introduction 1
2. Physical setting ................................................ 3
2.1 Geography ................................................ 3
2.2 Tides and tidal currents ....................................... 4
2.3 Winds .................................................... 6
General description .......................................... 6
Recent observations .......................................... 9
Model results ............................................... 12
3. Oceanography ................................................. 16
3. 1 Surface drifter observations .................................... 16
3.2 Suspended sediments ......................................... 17
3.3 Western Strait currents and water properties ....................... 22
Mean flow ................................................. 23
Variations ................................................. 25
Winter wind forcing ......................................... 25
3.4 Eastern strait-Sah Juan Island currents ........................... 31'
3.5 Plankton observations ........................................ 34
4. Oil-spill trajectory modeling ...................................... 36
4.1 Model description ........................................... 36
4.2 Sample trajectories .......................................... 37
5. Other studies. , * * * * ': , * ,**, * * ******* *,**** ** * * ,* *,*********,*, * 42
6. Summary and conclusions ........................................ 44
7. Acknowledgments .............................................. 47
8. References .................................................... 48

EXECUTWE SUMMARY

The Strait of Juan de Fuca is a major shipping driven currents, rather than tidal currents, domi-
route for both the United States and Canada. nate the relatively shallow water near Cherry
Tanker traffic is likely to increase in these waters Point, one of the major oil terminals in the region.
now that the Trans-Alaskan pipeline is complete. Drift cards released south of San Juan Island in the
Much new work has taken place since the publica- middle of the eastern basin of the Strait, an inter-
tion of the most recent oceanographic description section of major traffic lanes, were found on all
of this estuary over fifteen years ago. The present beaches surrounding the eastern basin. Drift cards
report was written at the request of the NOAA that progressed farther seaward tended to ground
Administrator to provide an up-to-date, compre- on Vancouver Island in winter and on the
hensive synthesis of results of the most recent Olympic Peninsula in summer. A computerized
studies for use in decisions regarding these waters. oil-spill trajectory model, while still incompletely
The primary emphasis of the NOAA efforts has developed, also indicated several possibilities of
been on transport mechanisms that might affect flow ending on beaches in the eastern basin.
the redistribution of spilled oil. Additional field Moored current meter observations in the western
studies east of Port Angeles are continuing basin showed that, during intervals of coastal
through 1978. storms, the surface currents flowed into rather
These studies have shown that a variety of than out of the Strait for a few days. This flow
transport processes exist in the Strait of Juan de was accompanied by intrusions of coastal ocean
Fuca that could result in considerable redistribu- water as far as 90 km from the mouth and reten-
tion of spilled oil, or any other contaminant, tion of surface water within the system. The speed
throughout the region. Winds appear to be the pri- and duration of the intrusions implied that ocean
mary factor causing significant variations in the water on occasion could possibly reach as far east
more normal net flow of surface water out to sea. as Whidbey Island.
In addition, winds appear to direct the flow There remain a number of unanswered ques-
toward the shores of the Strait. Large flow varia- tions. The flow patterns that distributed the drift
tions occur during every season but summer. The cards around the eastern basin are unknown.
evidence presented, while not yet complete, indi- Also, it is not clear whether the intrusions of
cates the strong possibility of significant volumes coastal water enter the eastern basin, or to what
of a spilled contaminant reaching beaches within extent storm-related conditions drive the circula-
the estuary instead of being transported out of the tion there. These questions are being addressed
estuary. The probability of such a beaching in- during the present field investigations. Another
creases significantly the farther iiRto the estuarine limitation is that the oil-spill trajectory model has
system the potential spill occurs. Likewise, the been run only for a typical March and no summer
probability of an accident leading to a spill in- cases have yet been run; additional calculations
creases with distance into the system because of are being made this year. Also, time has not
narrowing channels near the San Juan Islands and allowed inclusion of data on the winter current re-
intersecting traffic lanes north of Admiralty Inlet, versals in the model. As yet, little is known about
the entrance to Puget Sound. processes occurring in the near-shore zone extend-
Tidal currents are the strongest component of ing about a mile or so offshore throughout the
the flow in most of this estuarine system, and be- estuary, in the passages between the San Juan
cause of their large magnitude in the more re- Islands, at the mouth of the Strait, and at the junc-
stricted passages they are navigational hazards. tion with Admiralty Inlet. These areas must await
Tidal fronts form north and south of the San Juan future research.
Islands in waters that are major traffic lanes, and This report was used for environmental plan-
near-shore eddies and backwaters occur nearly ning even before the final draft was completed.
everywhere on the down-current side of head- The summary and conclusions were presented as
lands. Both of these phenomena tend to concen- "Comments on vessel traffic management-in Puget
trate floating or suspended material. However, Sound waters and environmental factors entering
current-meter and satellite observations of the therein" at U.S. Coast Guard hearings on April
Fraser River plume indicate that variable wind- 20-21, 1978, in Seattle.

1240 1230 Fraser R. 1220

Vancouver

0@1 CANADA
G. 490-
490 0
UNITED STATES

Vancouver Island
Cherry Point

i,Bellingham
111, San Juant-P
Islands

co 0
Victoria .0 Anacortes
Tatoosh 1.
0
Nea ay Juan Q7 ey Skagit R.
r'spe
1c'11,a Race
0al", Bee@h'
Rocks Z5
H ad

Port Angeles
-480 :480-

Quillayute Olympic Peninsula

0
W
Olympic Mountains 4C5
Seattle

Hood Can I

Tacoma

1240 123 1220
-47') 1470 _j
Figure 1. Strait of Juan de Fuca, showing nearby features and connect-
ing waterways. Additional place names in and north of the San Juan
Islands are shown in Fig, 39.

CIRCULATION IN THE STRAIT OF JUAN DE FUCA:
SOME RECENT OCEANOGRAPHIC OBSERVATIONS

G. A. Cannon, ed.

ABSTRACT. Oceanographic research in the Strait of Juan de Fuca and some of its adjacent waterways,
emphasizing transport mechanisms that might affect the redistribution of spilled oil, has focused on near-
surface circulation and its driving mechanisms. Moored current meters, surface drift cards, satellite
images of suspended sediment, and an oil-spill trajectory model were used. The largest flow variations
were found during fall-winter-spring. Drift cards tended to ground on Vancouver Island in winter, on the
Olympic Peninsula in summer, and on beaches in the eastern basin of the Strait throughout the year.
Trajectory model experiments also.showed flow ending on beaches in the eastern basin. Numerous tidal
fronts were observed north and south of the San Juan Islands, and near-shore eddies occurred everywhere
on the down-current sides of headlands. Both of these phenomena tend to concentrate floating or sus-
pended material. Moored current meters showed winter intrusions of oceanic surface water almost to
Port Angeles lasting several days to over a week. Outflow often occurred only in the deeper water, with
surface water being retained within the system. Winds appeared to be the major cause of all flow varia-
tions. Indications were that significant volumes of any contaminant would probably reach beaches within
the estuary,

1. INMODUCTION

The Strait of Juan de Fuca estuary is the prin- cause of the potential for increased tanker traffic,
cipal approach from the Pacific Ocean to the the primary objective of these investigations was
major Canadian and United States population to describe the important transport mechanisms
centers (Vancouver, Seattle, et al.) located on the that might affect redistribution of spilled oil. Field
Strait and on the adjacent waters of the Strait of studies included primarily physical oceanographic
Georgia and Puget Sound (Fig. 1). The region is a and meteorologic measurements to observe sur-
spectacular environment for living and recreation, face circulation and to determine causes for its
and its abundant resources provide a substantial variations. Because the surface and deeper water
base for economic development. Decisions on constitute a coupled system, some aspects of flow
questions regarding new and alternate uses of through the total water column also were
these waters require knowledge of various aspects measured. Additional studies included suspended
of the marine environment. However, the most re- sediment investigations partly using satellite ob-
cent description of oceanographic features of the servations, oil-spill trajectory model develop-
Strait of Juan de Fuca is more than fifteen years ments that included a coupled meteorological
old (Herlinveaux and Tully, 1961). While several model, and biological observations of seasonal
studies have occurred since then, most have been plankton distributions. The mooring studies dis-
limited to descriptions in isolated reports or have cussed in this report have been west of Port
not yet appeared in reports or scientific Angeles. Mooring studies east of Port Angeles are
publications. taking place during 1978 and cannot as yet be
In 1975 the Pacific Marine Environmental reported.
Laboratory (PMEL) of NOAA initiated investiga- Since the fall of 1973 the National Ocean Sur-
tions into several oceanographic aspects of this vey.(NOS) of NOAA has carried out several de-
system with major emphasis on circulation. Be- tailed circulatory surveys in the Strait of Juan de

Fuca, the Strait of Georgia, and the connecting presented here has come either from recently pub-
waterways through the San Juan Islands. The pri- lished reports or from studies that are in various
mary objective of their surveys was to obtain in- stages of being published. More details will be
formation on tides and tidal currents, along with found in the referenced reports, This report pri-
supporting auxiliary data. This information was marily describes studies conducted by NOAA
to provide Increased understanding of these water and, where appropriate, refers to other known
systems needed in general for safer navigation and work in the area. It emphasizes circulation and
more specifically for possible increased oil tanker water movement because the majority of recent
traffic. Some of these surveys have been carried research has been dominated by efforts in these
out jointly with PMEL investigators. NOS obser- areas. The Other Studies section mentions on-
vations presented in this report have been made going work east of Port Angeles. No attempt has
primarily east of Port Angeles and in the passages been made to relate this work to ecosystems
of the San Juan Islands. studies, and no implications have been drawn re-
The purpose of this report is to summarize and garding oil transportation or oil-port siting. Other
synthesize some of the scientific infor Imition of recent works have examined some of these topics
this recent oceanographic research in the Strait of (e.g., Little, 1977).
Juan de Fuca so that it is available in one source The Summary and Conclusions section is a brief
for environmental planning. Most of the material self-contained synopsis of this report.

2. PHYSICAL SETTING

2.1 Geography

The Strait of Juan de Fuca is a submarine valley the longitudinal density gradient (baroclinic forc-
extending from the Pacific Ocean to the channels ing). These two driving forces are balanced by the
of the San Juan Archipelago, Whidbey Island, and internal and bottom frictional forces generated by
Admiralty Inlet. It is bounded on the north by the strong tidal mixing.
low Seymour Mountains on Vancouver Island in Fresh water entering the inland waters is pri-
Canada and on the south by the higher Olympic marily river runoff, with the Fraser River account-
Mountains in Washington State. The Strait con- ing for approximately 80% of the total (Waldi-
tains two basins with depths exceeding 100 m. chuck, 1957). Precipitation varies considerably
These are separated by an effective sill (cross- (49-250 cm/yr) within the drainage basins. Most
channel ridge) projecting southward from Victoria of the drainage areas are high mountainous re-
at about 60-m depth. Seaward of this sill the outer gions, and winter snow storage plays a major role
(or western) basin deepens to more than 200 In at in establishing the runoff (Fig. 3). Precipitation is
Cape Flattery, and these depths continue seaward greatest during winter and at higher elevations,
along a glacial channel across the entire conti- but drainage does not occur until spring warming,
nental shelf. This western basin is about 20 km
wide and 90 km long. Landward of the sill is the DEPTH CONTOURS 49'
Eastern Strait of
deeper inner (or eastern) basin which connects to Juan cle Fuca
the Strait of Georgia primarily through Haro and
San Juan Archipelago
Strait with a secondary sill of about 90 m near the
-Fu 117. @ -I
north side of the San Juan Islands. Shallower 50
depths connect across the 64-m Admiralty Inlet
T
sill into Puget Sound. Intermediate depths are
found in Rosario Strait, which is the third main
passage of major shipping importance. This east-
ern basin topography is more complex with
numerous banks and shoals (Fig. 2). More details
are given by Parker (1977).
The western Strait of Juan de Fuca may be con-
sidered a weakly stratified, partially mixed -48
estuary with a surface-to-bottom salinity differ- 30' by
L
-30/oo (Herlinveaux and Tully, 1961). J
ence of 20/oo
Although there are important cross-channel varia-
tions, the along-channel mean flow is charac-
terized by the classical estuarine circulation with
seaward (westward) transport near the surface
and landward (eastward) transport near the
V",
bottom. This circulation is maintained by river k
water which enters the system and sets up a longi-
tudinal sea-surface slope directed toward the '@L@l
123'
mouth. The near-surface flow is driven primarily r
by the longitudinal sea-surface slope (barotropic Figure 2. Topography of the eastern basin of the Strait of Juan de Fuca
forcing) while the deeper return flow is driven by and the San Juan Islands waterways. Based on Parker (1977).

12
MEAN RAINFALL (1910-40)
0

E e
TATOOSH ISLAND
L) 6

_j
_j 4
La
Z 2

PORT ANGELES
0
500 2.2 Tides and Tidal Currents

MEAN RIVER
DISCHARGE Observations from various sources indicate that
(1958-72) FRASER RIVER
tidal currents dominate the flow regime in these
ME 200 - waters. Superimposed on the tidal motions are the
Uj estuarine and wind-driven currents that transport
floating and suspended material through the sys-

L
100- tem. The tidal currents represent navigational
)
hazards. In addition, they tend to disperse floating
SKAGIT RIVER and dissolved constituents away from shorelines
UJI
> and to concentrate those constituents in near-
cr 0 1 1 1 shore eddies and at tidal fronts.
32 - MEAN SURFACE WATER SALINITY Both the diurnal and semidiurnal tides enter the
system from the Pacific Ocean as progressive,
long waves. (Figs. 4 and 5 show the M, semkfi-
RACE ROCKS
- 30 - (1941-70)
0 urnal tide; the diurnal is in Parker, 1977.) Each wave
6_0 propagates through the topographically compli-
>_ cated San Juan Archipelago, producing a complex
28
current pattern in this region with strong currents
< in Haro and Rosario Straits (Fig. 6). Strong cur-
U) 26 EAST.POINT rents also occur in Admiralty Inlet as the tides
(1953-64) propagate into Puget Sound (Fig. 7). The tidal
current regime south of the San Juan Archipelago
24 (eastern basin of the Strait of Juan de Fuca) ap-
i F M A M i i A S 0 N D pears to be extremely complex. The volume trans-
Figure 3. Seasonal variations in monthly rainfall, river discharge, and ported through a cross-section near Neah Bay dur-
Surface salinity. From Holbrook and Halpern (1978). ing a flood tide is approximately 20 kM3 and
25 kM3 for the M, and K, components, respec-
tively, and the resulting tidal prism during spring
Consequently, the Fraser River has maximum dis- tides is nearly 2 % of the volume of the system
charge in June. Its winter mean discharge repre- (P. B. Crean, Environment Canada, personal
sents only approximately 12 % of its June peak. communication).
The Skagit River (the largest river emptying into Further analysis of the tide and tidal current re-
Puget Sound proper), however, has maximum dis- gimes in the Strait of Juan de Fuca, Strait of
charges in both summer and winter. The volume Georgia, and Puget Sound systems is underway at
of the maximum Fraser discharge in June over one the National Ocean Survey using a semi-analyti-
semidiurnal tidal period is less than 1% of the cal model, and at Environment Canada.using a
tidal prism (volume Qf water between high and numerical model. It is well established by the early
low tide levels). The spring freshet lowers the sur- work of Redfield (1950), as well as by more recent
face salinity north of the San Juan Islands at East work, that reflection of the tides in the Strait of
Point (east end of Saturna Island, shown in Georgia produces standing tides in that region.
Fig. 39) by several parts per thousand, while south Around the San Juan and Channel Islands (Cana-
of the San Juan Islands at Race Rocks, the surface dian), the tidal currents in any given channel are
salinity remains higher and undergoes smaller sea- often controlled by the differing water level at the
sonal and monthly variations. One important as- two ends of the channel. Because of their shorter
pect of tidal mixing in the passages of the San Juan wavelength, the semidiurnal tides such as M2 have
E

AN R IVE
M E@R@@
DS CHRGE
('9 58 72 @RAS R RIV@ER
'@'TR V'R

EIA S@l 0' N)T
'9_
.4

Islands is the moderating effect on seasonal fresh- minimums in their range near Victoria (Fig. 5)
water fluctuations, in the Strait of Juan de Fuca. while diurnal tides such as K, (not shown) have
Tidal mixing in Admiralty Inlet similarly progressively increasing ranges moving landward
moderates runoff entering from Puget Sound. from the Pacific Ocean.

124' M*

COTIDAL LINES FOR M2 TIDE
50' E -- .1 d-
1. 12N -idj..
D-d

49'
.2*

15b Al

48' W
IL%* IZ5, 124' M In'

Figure 4. Cotidal line chart for the M. tide in the Strait of Juan de
Fuca-Strait of Georgia system. From Parker (1977).

M8, w 125' 30' 124' w 123'

F.RA.DE UNESIO. -2 TIDE]

49'
@A
5.o
ftA
4.8

3,8 44

Victoria 9 1 40 w
3.4 4
4.2 36

18 2 3.4
3A

4R.
123' 122.

Figure 5. Corange line chart for the M2 tide. From Parker (1977).

49o 49@
13
124-30' 124' 12 30' trait o U1 213o
S f
Georgia

Vancouver Island
4,

San Juan
"Sa.
Archipelago

/Y
48 48
30
30'

0
it Of
Juat? cle 'cl,

1240 30' 1 14o 12300-

Figure 6. Tidal current ellipse chart for the tide in the Strait of Juan de
Fuca-Strait of Georgia system. Direction ellipse points indicates
direction of tidal current flow. Size of ellipse indicates intensity of
flow. From Parker (1977).

While a regional description of the tidal range Georgia, internal waves are formed during flood
appears to be reasonably accurate, the tidal cur- tides. The currents associated with these waves
rents appear to be much more sensitive to local change across the shallow pycnocline formed by
variations in water depth and details of the shore the Fraser River effluent (Gargett, 1976).
line than are the tidal ranges. For example, the
tidal currents near Cherry Point are relatively
small (Schumacher et al., 1978), while much 2.3 Winds
stronger tidal currents occur offshore from Cherry
Point and in the passages leading to the Strait of General description. Major perturbations
Juan de Fuca (Fig. 6). On the other hand, the tidal to the seaward, near-surface estuarine flow can
ranges showed much less variation (Fig. 5). occur as a result of the near-surface wind field.
Moored current meter arrays do not allow a de- Wind stress can act directly on the surface, trans-
tailed analysis of tidal fronts or discontinuities, ferring momentum or energy downward by ver-
but these can be observed in aerial and satellite tical mixing. It also can act indirectly by raising
images. Such fronts are common near points of the sea level at the mouth of the estuary (piling up
land in the Strait of Juan de Fuca-Puget Sound re- water) and thereby modifying the sea-surface
gion (C. A. Barnes, University of Washington, slope within the estuary, which in turn dominates
personal communication; see Section 3.2 below). the near-surface circulation. Thus, knowledge of
Tidal fronts act as down-welling centers where local and adjacent wind fields is essential to any
floating material such as oil could be injected into description of near-surface water motion. The
the deeper layers of the water column. Vertical conventional directions from which the wind
dispersion also occurs in passages with strong blows are used in the following description.
tidal currents, which produce mixing through the The predominant winds along the ocean eoast
generation of turbulence. are southwesterly (i.e., from the southwest) in
The vertical distribution of the tidal currents is winter and northwesterly in summer, paralleling
relatively simple in the Strait of Juan de Fuca and the general coastline, and this pattern is reflected
in the passages through the San Juan Archipelago. in measurements of typical winter and summer
In these regions, the tidal currents are relatively mean wind stress fields off the Washington coast
independent of depth near the surface, decrease in (Nelson, 1977). In the Strait of Juan de Fuca the
amplitude below the surface layers, and form a winds are controlled by orographic factors. In
bottom boundary layer with active generation of general, seaward or easterly winds dominate in
turbulence during strong current intervals. To the winter while landward or westerly winds occur
north of the passages in the southern Strait of more frequently in summer (Harris and Rattray,

Whidbe I
Y
. . . . ... ... @,O

_'V

\v v
4,111-@
V\,

N
xPA
A
�
49L,1

-A

j
N
X,

VV`
TN

Figure 7. Artist's rendering of surface tidal currents during flood tide in
Admiralty Inlet as observed in a hydraulic model of the Puget Sound
system. From McCary and Lincoln (1977).

The winter season (December-February)
weather is dominated by cyclonic storms moving
50 over or to the north of the region, interrupted in-
PERCENT WIND SPEEDS frequently by periods of high pressure. Gale force
40 TATOOSH ISLAND ? 8.5 .. SeC_1 (17-24 m/sec) or higher winds occur frequently
1- (1948-1958)
UZ30 near Tatoosh Island with southerly gales persist-
two or three days accompanied by high sea
ing
W20 20.3%
and swell. While it is difficult to generalize all
10 PORT ANGELES weather types, there seem to be two typical storm
5,2%
0 patterns. In the first, pressure patterns are asso
J F M A M i J A S 0 N D ciated with a large low-pressure area in the Gulf of
TATOOSH ISLAND PORT ANGELES Alaska (Fig. 9-A). The center of the low pressure
20 ZO is usually stationary with the frontal system
15 WINTER 15- WINTER moving rapidly across the Pacific. Often the cold
(TOTAL = 38.0) (TOTAL- 5.2) front will rapidly approach the coast, stall, dissi-
10 10- pate offshore, and then move inland, leading to
Z 5 5- difficulties in providing forecasts. The second type
0 of storm includes disturbances that form in the
0
10 central Pacific between the Aleutian low and the
SUMMER SUMMER Central Pacific high and skirt across the Pacific,
5- (TOTAL = 3@8) 5 - (TOTAL = 6.4) commonly on an east-northeasterly trajectory,
0 P=r,,,. 1 0 -@ ..... r@' reaching land over Vancouver Island (Fig. 9-B).
N E 5 W N E S W Such systems are steered by a strong westerly
Figure 8. Seasonal distribution of winds greater than 8.5 m/sec at component in the flow at upper levels in the at-
Tatoosh Island and Port Angeles. From Holbrook and Halpern
(1978). Winter and Summer histograms are for December-February mosphere. Occasionally the large-scale flow
and June-August, respectively. pattern of upper air will shift as it did in winter
1976-77 when the storm track occurred to the
1954). The seasonal variation of winds at Tatoosh south of Oregon. For frontal systems associated
Island off Cape Flattery shows that during winter with low-pressure centers passing to the north of
months 38% of all winds observed have speeds the Strait of Juan de Fuca, the general pattern of
greater than 8.5 m/sec (Fig. 8). The southerly and surface winds just offshore is prevailing south to
easterly directions shown in the Tatoosh histo- southwesterly flow backing to west-northwest as
gram suggest that winter winds reflect the com- the cold front passes. At some time during most
bined influence of the large-scale wind systems winters an upper level ridge of high pressure will
along the coast and the locally steered winds in the develop over northwest Canada (Fig. 9-C). This is
Strait. In contrast to Tatoosh, during winter accompanied by a surface high over Puget Sound
months at Port Angeles only 5% of the wind basin. The corresponding weather includes clear
speeds are greater than 8.5 m/sec. The Port skies, near-freezing temperatures, and very stable
Angeles winds are generally westerly which is con- air in the surface layer. Winds in the Strait are
sistent with the apparent divergence region west of from the east, increasing in magnitude from east
Port Angeles suggested by Harris and Rattray. to west.
However, about 1%-2% of all observations Summer is characterized by the offshore build-
showed strong northeasterly winds. up of the eastern Pacific high pressure (Fig. 9-D).

H
OL

A B C D
H)
A@H

Figure 9. Typical storm patterns affecting the Washington coast.
Adapted from Maunder (1968) in Overland and Vimont (1978).

The high pressure leads to a dry season with many Recent observations. During the late winter
clear days and prevailing winds from the west to of 1976 (February-May), the winter of 1976-1977
northwest. Superimposed upon the mean flow is a (November 1976-February 1977), and the summer
strong diurnal oscillation associated with the sea of 1977 (June-September), over-the-water and
breeze. Victoria and Port Angeles show a compo- shore-station wind measurements were made in
nent of wind continuously from the west with conjunction with current observations in the west-
maximum speed occurring at about 1800 local ern basin of the Strait, as described in the
time and near zero speed in the early morning Oceanography section. Over-the-water winds
hours. Over 75% of all wind observations during were measured from surface buoys located at Sites
the summer months at Port Angeles are from the A, B, and C (Fig. 12) and were recorded by vec-
western quadrant. tor-averaging wind recorders. Details of the meas-
The spring season is not significantly different urement techniques and preliminary analysis are
from winter except that temperatures begin to rise, given in Holbrook and Halpern (1978).
the frequency of cyclonic disturbances decreases, The predominant wind patterns during the three
and their distribution over time is irregular. The deployments were different (Fig. 13). During the
autumn season is another transition period. A first winter's deployment, coastal winds were
common characteristic of early fall is an Indian southwesterly, while Strait winds were westerly as
summer, the result of continuing high pressure. measured at Race Rocks and Port Angeles. No
Topography plays the major role in influencing over-the-water winds were recorded. During the
the winds in the Strait of Juan de Fuca. Due to the second winter experiment, coastal winds were
rotation of the earth, winds tend to blow clock- southeasterly, and Strait winds measured from the
wise around a high and counterclockwise around surface buoys were predominantly easterly, in
a low as viewed from space in the northern hemi- contrast with the winds of the first winter. During
sphere. However, in places where topography pre- the summer experiment, Strait winds measured
vents the free flow of air, such as the passageways from the surface buoys were westerly with a
of northwest Washington, winds invariably blow strong diurnal sea-breeze component. The second
from high to low pressure in a direction dictated winter generally was analogous to that described
by the orientation of the terrain. The Strait of Juan by Harris and Rattray (1954), while the mean con-
de Fuca is very prone to this type of channeling ditions during the first winter were entirely dif-
since the air is often stably stratified, decreasing ferent.
the possibility of vertical motion of air parcels. For During the first winter experiment, winds were
example, when winter high pressure exists in the measured at NOS and Environment Canada shore
interior of Washington State, the pressure is stations (Fig. 14). The two most predominant win-
higher inland at Bellingham than at Quillayute on ter wind patterns occurred on February 15 and
the coast (Fig. 10). The airflow accelerates March 3, 1976. The first was characterized by
through the Strait with the weak winds at Port southerly winds off the coast (Tatoosh Island) and
Angeles, and strong east winds at Tatoosh. These over the inland waters (Point Wilson at the en-
are the so-called gap winds (Reed, 1931). Winds trance to Admiralty Inlet and Smith Island) and
are from the north -in the Puget Sound-Seattle weak and variable winds over the middle Strait
area. (Port Angeles, Race Rocks, and New Dungeness
The local air flow is complicated further by spit east of Port Angeles). On March 3, winds at
inertia, the tendency of the air to flow in the same all stations were northeasterly and were generally
direction. Just before the passage of a storm with associated with a high pressure system located
coastal winds from the southwest, the flow is over the Cascade Range.
channeled through Puget Sound and around the Other statistical studies showed that the total
Olympic Mountains (Fig. 11). However, the air wind variance was 81 % greater during winter
flow overshoots in the lee of the mountain form- than during summer. The along-channel wind
ing an area of calm winds in the vicinity of Port variance accounted for most (76%-84%) of the
Angeles. As the storm moves northeastward the total variance and was primarily distributed at
winds in the Strait shift to westerly and the con- lower frequencies with 87%-90% below 0.04
vergence zone formed in the lee of the mountain cycles per hour (cph). The only significant spectral
moves south. This case of westerly winds in the peaks occurred during summer and were asso-
Strait was typical during one of the winter series ciated with the sea-breeze effect. Of the along-
of recent observations described below and later channel variance at frequencies below 0.04 cph,
in Section 3.3. These westerly winds appeared to 72%-85% was coherent between Sites A and C,
be a regularly occurring event during winter. and phase lags in this frequency range were not
Other examples are in Overland and Vimont significantly different from zero. Of the along-
(1978). channel total wind energy, 56 % -74 % was linearly

Bellingham

0@0
'a-\ 0420
7 Strait of
uan de Fuca
0"f-

Quillayute Port geles
40*
N N
11106

Olympic
Mountains
Seattle
A '13

,f70

0710

0701

01 DEC 76
2705 OWO GMT

12 5' 12 123'W

Figure 10. Sample wind patterns with interior high pressure. Barbs on
wind arrows each represent 10 knots (5.1 m/sec). From Overland and
Vimont (1976).

J Z4*'

m2
If9 17031 ID

jo1 0 Bellingham

Tatoolsh 2%iy
1. -As

Strait of Juan cle Fuca

Quillayute Port Angeles
4e-
N N

Olympid
Mountains 0

M Seattle
= I
0-

09 DEC 76
clow oT

07
Isis
125' 12 [3 IW

Figure 11. Sample wind patterns during southwest storm winds on the
coast. From Overland and Vimont (1978).

'1ZI
VANCOUVER ISLAND
k' W%
f.N'
Kt.
SAN@J
ISLAD
183 m
30'-
VICTORIA@

CA E
FLATTERY NEAM,-
SMITH QJ
BAY
RACE
-RK

Q In
48
to
P6RT . . ....
ANGEL
WASHINGTON ES

12 4* 123o
Figure 12. Surface mooring locations A, B, and C. From Holbrook and
Halpern (1978).

correlated over the length of the western Strait of 1 mb/200 km. The best estimators of along-
(70 km). Winter correlation coefficients channel winds in the western Strait were found to
(0.86-0.90) were higher than summer (0.75-0.84). be the atmospheric pressure difference between
The across-channel wind components were not Bellingham and Quillayute airports and the regu-
significantly correlated between Sites A, B, and C. larly measured winds at Race Rocks.
During summer only, wind speeds increased with Further discussion of the marine meteorology of
up-channel (landward) distance due to orographic western Washington is given in Overland and
funneling (first suggested by Reed, 1931) and pos- Vimont (1979), Holbrook and Halpern (1978),
sibly with increased strength of the sea breeze. Lilly (1978), Maunder (1968), and Phillips (1966).
Correlations between over-the-water winds and Also, a new technique of airborne wind measure-
shore-station winds showed north-south compo- ments recently has been developed for application
nents were not significantly correlated. The east- to atmospheric models and/or oil-spill prediction
west components were in general significantly cor- (Oliver and Gower, 1977).
related with those measured at shore stations.
During winter, east-west winds at Race Rocks and Model results. The winds over western
Tatoosh Island were most representative of west- Washington are dominated by the effects of
ern Strait winds over the open water. During sum- topography. The Strait of Juan de Fuca, being a
mer, comparisons were best with winds at Race narrow cut in the coastal mountains between
Rocks and Sheringham Point. Winds measured on Puget Sound and the ocean, is particularly rich in
Ediz Hook at Port Angeles during winter were local features with large changes in wind speed
least representative of winds over the water. and direction over sho-rt distances. The location
The atmospheric pressure difference between and shape of these features are continually chang-
Bellingham, located northeast of the San Juan ing in response to the changing large-scale weather
Islands, and Quillayute, located on the Washing- situation. Thus, a major limitation of coastal
ton coast, was assumed to be representative of the meteorological forecasting is the inadequate speci-
longitudinal atmospheric pressure gradient fication of the local wind field at the spatial resolu@
(Fig. 15). Hourly and low-pass filtered values tion necessary to resolve wind drift, local waves,
were strongly correlated with the along-channel and vessel or oil-spill leeway. Typically, this is
component of winds measured at Site B and at due to the difficulty of estimating near-shore wind
Race Rocks. Out-channel winds occurred when at- fields directly from large-scale pressure patterns or
mospheric pressure over inland regions (Belling- from widely scattered and often unrepresentative
ham) was greater than over the Pacific coast wind measurements. To this end a numerical
(Quillayute). Maximum (above 10 m/sec) winds meteorological model was developed for use in
were associated with pressure differences in excess conjunction with the field measurement program
of 4 mb. There was a correspondence between to determine regional wind patterns for the oil-
along-channel winds with speeds of 2.5 m/sec and spill trajectory model (described below in Sec-
the along-channel atmospheric pressure gradient tion 4) and to explore the physical processes that

125*00' 30' 124'00' 30' 123*00 30' 122100'
n

30-
30'
2.3

1A
3.0 1.4
its 1. 1. 3 1.2

48-
411'
00@ 00

FEB-MAY 7

125* 00' 30' 1249W 30' 123'00' 30' 122*00'

1250 Od 30' 124100' 30@ 123100 30' 122'00'
,00, b
Q@

30- 3.6 30'
NO
3.5 "tar,
2.5
2.3

W 48*
OC@ L:
00'

-FE
NOV 76 8 77

t 125000' 30' 124?00' 30' 123'00' 30' 122*00'-

125000' 30' 124*00' 30' 123'00 30' 122100'

30- 30'

2.4
5.7
5.3

41r 48'
00@ 00'

JUN-SEP 77

125* 00' 30' 124oW 30' 123*00' 30' 122'00'

Figure 13. Vector mean winds (m/sec) during each of the three experi-
ments showing direction to which the wind blows. From Holbrook
and Halpern (1978).

TATOOSH ISLAND
-10
10

SLI P POINT
-10
10

0
RACE RO@CKS
10

C)
a)0
U)
EPORT ANGELES
-10
10

0 "A

NEW DUNGENESS
-10
10

0 //NPIP-11111 N11111
-101SiMITLHI IS LA IND
10

0
_10- POINT WI L SON
15 20 25 1 5 10 15 20 25 30 1 5 10 15 20 25 30
1976 FEB MARCH APRIL
Figure 14. Low-pass filtered wind vectors measured at shore stations
during the first winter experiment and plotted at 6-h intervals. From
Holbrook and Halpern (1978). The vectors point in the direction
Aoward which the wind blows.
20 -ALONG-STRAIT WINDS AT STRAIT-4
10 -

0-
E-10-

-20- ................
20 -
ALONG-STRAIT WINDS AT RACE ROCKS
IO_
U
0
E-10-

-20 1 ............................
6-
4- ATMOSPHERIC PRESSURE DIFFERENCE (BA-QA)
2-
0-
-2.
-4
-6 ..........
1040 -

1020-

M
1000 -
ATMOSPHERIC PRESSURE AT QUfLLAYUTE (OA)
960 .............. ib .... 2@ .... 3'Oi ... .... ID .... 1'5' ........
510 15 20 25 36'i Ib .... I@... 2b .... 2@ .... 3Y i ... .... I'D
NOV DEC JRN FEB
76 76 77 77
Figure 15. Along-channel winds related to the atmospheric pressure dif-
ference between Bellingham (BA) and Quillayute (QA) showing
hourly and low-pass filtered values. From Holbrook and Halpern
14 (1978).

VELOCITY VECTOR PLOT E OC TY VECTDR PLOT

I J J
,TTq]T TT 1.
XTT

T
>

I t t I

r rr tft I T 70 11 14
I t r t
t
I"It I. t'
tr17 1 ? Tr
T
t t
r

lilt

T I

r T T
llpm t t T 'T

ffrr
Itr T I
11/1 7 Ir
I. . . . . . . . . .. X t@

I tip r tr IIIe
it r I
7
7 t

I !ET,TIJ _n
I j..
rT I

tT I
rrrt t

10 METERS PER SECOND 10 METERS PER SECOND

Figure 16. Sample model winds showing easterly winds in the Strait of Figure 17. Sample model winds showing southwesterly.winds along the
Juan de Fuca. From Overland et al. (1978). coast. From Overland et al. (1978).
create the local patterns. The intent of the model offshore which further accelerated the flow in the
was first to specify the large-scale pressure field, Strait to speeds much greater than would be esti-
stability of the air, local land elevations, and the mated for simple geostrophic flow with the same
distribution of land and water, and then to use the pressure gradient. The model indicated a general
equations of momentum to estimate the local wind flow of air out of the Puget Sound basin at the sur-
field. A complete description of the model with face with replacement of the air by subsidence
initial validation experiments is given in Overland from above.
et al. (1978). The model domain extended south to Figure 17 shows a case for southwesterly flow
include all of the Olympic Mountains, because it typical of the synoptic situation before the passage
was determined that the winds in the Strait of Juan of a cold front (Fig. 11). The local wind vectors
de Fuca were sensitive to the volume of air Show the channeling by the Cascade and Olympic
channeled through Puget Sound. Mountains. Winds over Puget Sound were
Figure 16 shows the result of running the model stronger and more southerly than offshore. A re-
for the case of east winds in the outer part of the gion of light winds was evident in the lee of the
Strait (Fig. 10). High pressure was to the east of Olympic Mountains, which the model interpreted
the region. Major features were light northerly as a locally induced low-pressure center. Similar
winds in Puget Sound and the strong winds in the numerical experiments indicated that the position
western end of the Strait of Juan de Fuca. Stability of the eddy and the magnitude of the pressure
restricts the flow to regions below the mountain- gradient that developed along the axis of the Strait
tops where the air is accelerated along the east- of Juan de Fuca were very sensitive to the volume
west pressure gradient out through the Strait of of air channeled through Puget Sound, which de-
Juan de Fuca. The divergence of the air flow after pended in turn on the orientation of the offshore
reaching the ocean created a local low pressure flow.

t' I>

SITE: 02
CARDS: 0051-0100
LATITUDE: 48-17.8 N
LONGITUDE: 124-04,1181 W
""L 197
PATE: 5 APRIL 1976
4
42.'.
'RETURNED7

3. OCEANOGRAPHY

A
3.1 Surface Drifter Observations

A program of surface drift cards, or drifters, During the summers of 1976 and 1977 releases
was initiated to determine potential flow trajec- were distributed along the entire Strait of Juan de
tories in the Strait of Juan de Fuca and Puget Fuca. The general drift was similar in both years.
Sound systems. During six cruises in 1976-77, There was a seaward migration of most cards re-
5000 drift cards (flat plastic cards about 6 by leased near the mouth of the Strait into the Pacific.
12 cm) were released throughout the Strait and Cards exiting the Strait immediately grounded on
parts of Puget Sound at 55 sites when conduc- the north coast of Washington or were lost to the
tivity-temperature-depth observations were being study. Of those released in the eastern Strait, few
made or when current-meter stations were de- apparently reached the ocean. Recovery was high,
ployed or recovered. All releases were south of the and most cards were found within a few tens of
passages between the San Juan Islands. Of the kilometers of the release point. Cards were found
total released 29% had been recovered as of on Whidbey Island, the San Juan Islands, and
November 1977. Many of *the cards were covered along the south coast of the Strait (Fig. 18-C).
with oil and tar at time of recovery. Total re- Both summers showed this same pattern. Cards
coveries from the Sound and Strait have been 40% released within Puget Sound flowed out Ad-
and 20%, respectively. Cards released in the Strait miralty Inlet into the eastern Strait and then were
had a greater chance of reaching the ocean and dispersed similarly around the eastern Strait
hence were lost to the study as indicated by the basin. Releasescloser to the southern shore of the
generally lower percentage recovered. Seasonal entire Strait moved seaward and tended to ground
dependence for recoveries was less clear. How- on the southern shore (Fig. 18-E).
ever, recovery distributions appeared consistent
with seasonal wind patterns. The releases which grounded on the U.S. shore
There was an overall tendency for cards re- in July 1977 were concurrent with a tracked drifter
leased in the Puget Sound-Strait of Juan de Fuca study in the western Strait (Ebbesmeyer et al.,
system to migrate seaward. This is because near- 1977). Their tracked drifters experienced an
surface transport resulting from the estuarine cir- across-channel flow to the south under the influ-
culation within the system generally moves sea- ence of a diurnal fluctuating west wind during
ward. For all ca'rds released, approximately 24% each of three days. Releases were made between
of the recoveries were from locations seaward of Slip Point and Pillar Point only on the southern
the release site; 7% were from areas landward of half of the Strait and were tracked only during
the release site; and the balance were from loca- daylight hours. During ebb flow the tracked
tions in the general vicinity of the release site. A drifters moved parallel to the shore, and during
mean seaward drift of 6 km/day was calculated flood they moved toward the shore. No sightings
and the cards appeared to be waterborne for days or recoveries were reported on or near Canadian
to weeks. The majority of the drifters from the shores. There was a dominance of occurrences of
interior of the Puget Sound-Strait of Juan de Fuca beachings in the lee of Slip Point and in the lee of
system were returned in 2-4 days by people who Pillar Point, which indicated that these were pos-
found them and responded to the message on sible entrapment areas. Drift card responses de-
them, and those drifters exiting the system were scribed by Pashinski and Charnell from this same
returned within 3-4 weeks. More details of the period were predominantly under the same wind
program and computational techniques are de- influence. During winter 1977 cards were released
scribed by Pashinski and Charnell (1978). primarily in the western Strait basin. This release

SITE' 11 SITE: I
CARDS: 0501-0600 CARDS: 1101-1200
LATITUDE: 48-16.0 N LATITU DE: 48-01.7 N
LONGITUDE: 123-03.8 W LONGITUDE: 122-37.5 W
DATE: 14 APRIL 1976 DATE: 22 JULY 1976
RETURNED: 49% RETURNED: 53%

B C

represented the highest number of cards deployed
at any time and the lowest return rate (13%). The
majority grounded along the west coast of Van-
couver Island but a few moved out of the Strait,
then south along the northern Washington coast
(Fig. 18-1)).
Spring releases were made both years through-
out the Strait. There was a high incidence of re-
covery along the Washington-Oregon coast from SITE: 21
both eastern and western Strait releases, but very CARDS: 1501-1600
LATITUDE' 48-13 3 N
few cards were recovered along Vancouver Island LONGITUDE: 123-'14.4W
outside of the Strait (Fig. 18-A). Recoveries for DATE: 15 FEBRUARY 19
those released in the eastern Strait exhibited a RETURNED: 20%
pattern identical to a summer release shown
earlier (Figs. 18-C and 18-B), except for the added
large incidence of coastal recoveries in spring.
Current observations farther west, described in D
Section 3.3, showed weak currents at this time. I
Cards released at one eastern station in the Strait
were blown due east by high west winds, and 93 of
100 cards were found along a short stretch of
beach on Whidbey Island. Cards released in
Admiralty Inlet moved out into the eastern Strait
and spread out as described above for summer re-
leases. More work is needed to determine the dis-
persion paths between release and recovery sites
within the eastern basin of the Strait (e.g., Fig.
18-B).
SITE: 49
CARDS: 43Dl-4400
LATITUDE: 48-14.4 N
3.2 Suspended Sediments LONGITUDE' 123-45.7 W
DATE: 20 JULY 1977
RETURNED@ 13%
Baker et al. (1978) studied the surface trajec-
tories of sediment plumes originating from the
Fraser and Skagit Rivers. These plumes are
natural tracers of the flow patterns of the fresher
water that is discharged into the Strait of E
Georgia-Strait of Juan de Fuca system. Where the L I
plumes meet saline water, there is an abrupt
change that is marked by a sharp edge between the
river water and the darker sea water. The water
Figure 18. Surface drifter recovery locations for various release sites
masses separated by this frontal surface also have and times. From Pashinski and Charnell (1978).

I f.4
4
@gw

ph
- Aki
77`10" 4'@

Figure 19. MSS Band 5 of LANDSAT image 1727-18290, showing a Arm of the Fraser appear to flow to the northwest and to the north-
southeasterly dispersal (5) of suspended sediments from the Fraser east into Burrard Inlet (6). A cyclonic eddy (7) can be observed north
River into the Strait of Georgia on July 20, 1974. Time of image ac- of Galiano Island. Sediment discharge from the Skagit River into
quisition was 1029 PST, between major ebb current and slack water. Skagit Bay (8), and from the Nooksack River into Bellingham Bay (9)
The dispersal pattern suggests movement of Fraser River sediments is clearly visible. Several tidal fronts are also observed in the Strait of
along Saturna, Mayne, and Galiano Islands and into Trincomali Juan de Fuca. From Baker et al. (1978).
Channel from Porlier Pass. Suspended sediments from the North

differing veloc ities, and where the surface veloci- vessel, the data were not entirely synoptic and
ties are convergent, there must be downward, were integrated over several tidal cycles. In order
movement at the front. For example, oil spilled in to obtain synoptic information about plume
Delaware Bay, between Delaware and New trajectories, a set of LANDSAT satellite images
Jersey, moved toward fronts and spread out along from 1972-1977 has been examined. The sediment
them (Klemas and Polis, 1976). The combination plumes in the LANDSAT images appeared lighter
of downward motion with the presence of sus- in tone than the lessturbid water. However, the
pended particles to which oil might attach suggests LANDSAT imagery only provided information
that a convergent front is the place where oil about the upper few meters of the water column.
would be most likely to sink below the surface, Fortunately, previous studies have shown that the
greatly increasing the hazard to marine life. brackish water is generally confined to the upper
Suspended matter concentrations and composi- 5-10 m (Waldichuck, 1957). Therefore, the
tions determined by using water samples collected LANDSAT imagery could be used to study the
in situ with 10-liter Scott-Richards bottles have migration patterns of the brackish water, provid-
been used to describe the seasonal variations of ing' the sediment loadings were sufficiently higher
particulate distributions. However, due to the than the surrounding water. The amount of useful
physical limitations of operating from a single information about seasonal variations of sus-

@AX

V
LL_ 4
or,

Figure 20. MSS Band 4 of LANDSAT image 2417-18220 on March 14,
1976. Time of image acquisition was 1022 PST, between minor ebb
current and slack water. The image shows limited dispersal of sus-
pended sediments into the nearshore waters south and southeast of
the mouths of the Main, Middle, and North Arms of the Fraser. From
Baker et al. (1978).

pended sediment distributions and dispersal the river. Tidal mixing was rapid and numerous
patterns that can be obtained from LANDSAT eddies could be seen. Also, the Skagit River plume
imagery is somewhat limited because most cloud- flowed into Skagit Bay and Saratoga Passage dur-
free days occurred during the summer; as a result, ing the summer months. Some plume material
the majority of available images were from that passed through Deception Pass into Rosario Strait
season. Computer enhancement of images is being during ebb tide.
developed for future work. More details of the
overall program and of the techniques of using the The winter plumes from the Fraser and Skagit
LANDSAT images are in Baker et al. (1978). Rivers, as shown by the three images LANDSAT
During summer the southward flows of the was able to make in wintertime between January
Fraser River's Main Arm (south) and Middle Arm 1973 and March 1976, were much less distinct and
were so strong that the resultant plume main- less well-defined than the summer plumes
tained its identity for a considerable distance and, (Fig. 20). For instance, the Fraser River plumes
in some cases, traversed the entire length of the were only visible in the near-shore regions just a
Strait of Georgia (Fig. 19). Depending upon local few kilometers seaward of the river mouth, where
changes in tidal currents, the plumes extended the primary flow pattern was to the southeast.
either southeast or southwest from the mouths of During this period, the discharge of both water

-V
13

Ki L:C

Figure 21. MSS Band 5 of LANDSAT image 546S-17484, showing a Saturna Islands (11), and into Rosario Strait from the southeastern
southeasterly dispersal (10) of suspended sediments from the Fraser Strait of Georgia (12). Suspended sediment discharging into the Strait
River into the Strait of Georgia on July 27, 1976. Time of image ac- from the North Arm of the Fraser appears to flow northward past
quisition was 1048 PST, between major ebb current and slack water. Point Grey, where it bifurcates, a portion flowing to the northwest,
The dispersal pattern suggests movement of Fraser River sediments and the remainder flowing to the northeast into Burrard Inlet (13).
into Haro Strait from the passages on either side of Mayne and From Baker et al. (1978).

and suspended sediments was at a minimum, re- Middle Arm initially flowed seaward in a south-
sulting in dilution of suspended sediments to back- westerly direction, and then were diverted in a
ground levels. These conclusions were substan- southeasterly direction by the ebb flow in the
tiated by the results of the seasonal surveys of sus- Strait of Georgia (Fig. 19). The sediment plumes
pended matter concentrations in the vicinity of the migrated with the flow across the Strait and under
Fraser River. The winter decreases of fresh water the influence of tidal and Coriolis forces flowed
and sediments were less for the Skagit River, and through various passages and eventually into
seasonal variations in the Skagit River plume were Haro Strait. Occasionally the tidal flow was so
not nearly so pronounced. This material mixed strong that the sediment plume could be traced as
rapidly with the offshore water, and the winter far east as the passage between Orcas and Lummi
plumes did not maintain their identity beyond De- Islands (shown in Fig. 39) and ultimately into
ception Pass. Rosario Strait (Fig. 21). However, prevailing
The LANDSAT satellites have produced eight northwesterly winds at about 14 m/sec may have
or nine high-quality images which can be used for augmented this effect. Numerous cyclonic and
describing tidal effects on the dispersion of the anticyclonic eddies were associated with the
Fraser River plume. During ebb tide, distinct sedi- plumes. For instance, a cyclonic eddy observed in
ment plumes originating from Main Arm and the region north of Galiano Island (next island

_@4

Figure 22. MSS Band 5 of LANDSAT image 2129-18254, showing a
southwesterly dispersal of suspended sediments from the Fraser River
into the Strait of Georgia on May 31, 1975. Time of image acquisition
was 1025 PST, just after flood current. An anticyclonic gyre can be
observed due west of Point Roberts (3). Sediment discharge from the
Nooksack River can be seen in Bellingham Bay (4). Image is free of
cloud cover. From Baker et al. (1978).
northwest of Mayne Island, Fig. 39) appeared to Galiano Island. There is evidence for small
be detached from the major plume emanating cyclonic and anticyclonic eddies in the plumes
from the Fraser River. It probably represented a associated with the flooding tide. The sediment-
relic plume that moved into the region during a laden plume from North Arm flowed to the north
previous tide. The sediment plumes emanating and into Burrard Inlet during flood tide.
from the North Arm of the Fraser during ebb tide The LANDSAT images showed fronts separat-
in Figs. 19 and 21 flowed to the north and west, ing light-colored', particle-laden river water from
and a portion of the plumes flowed to the north- clearer, darker sea water. There also were light
east into Burrard Inlet (immediately north of the streaks that must show the concentration of par-
mouth of the Fraser's North Arm). ticles or of foam and debris at the convergence of
The sediment plumes originating from Main water masses having different directions of
Arm and Middle Arm during flood tide initially motion. Fronts of this type frequently appeared in
flowed seaward in a southwesterly direction the Strait of Juan de Fuca at the entrance to Haro
(Fig. 22). However, instead of being diverted to Strait, forming parallel arcs east of Victoria and
the southeast, as is the case during ebb tide, they south of San Juan Island. Fronts separating two
07@

were driven by the flood current across the Strait colors were seen in the western Strait of Juan de
and to the northwest along the northern coast of Fuca, stretching from Vancouver Island across to

. ..........
VANCOUVER r
ISLAND
VANCOL ER
IV MAXIMUM FLOOD
ISLAND
0100 hr& 16 MARCH.1973
M MUM EBB
MA
FRASER
qKCH-1 3 R RASER
UVER
IVER
4-
"Mn

IM _z

17, t
Ll

MITI

Z-
1-11 Ilk

Figure 23. Composite sketch of fronts seen in 24 LANDSAT images dur- Figure 24. Composite sketch of fronts seen in 9 LANDSAT images dur-
ing ebb tides. Adapted from Crean (1978) for this report by Sawyer. ing flood tides. Adapted from Crean (1978) for this report by Sawyer.

the Olympic Peninsula in a southwesterly direc- flood, and they reasonably explained the spacing
tion. On one occasion a pair of parallel curved of fronts that crossed the Strait of Juan de Fuca
fronts crossed the Strait about So km apart. These and San Juan Island passages.
had a parabolic form similar to flow in a pipe or
channel, with faster flow in the center and slower 3.3Western Strait Currents and
flow toward the boundaries.
The sharpest and most obvious fronts seen on Water Properties
LANDSAT images of the Strait of Georgia and the
Strait,of -Juan de Fuca have been sketched on The western Strait of Juan de Fuca is the rela-
charts of tidal currents from a barotropic model of tively straight reach extending about 90 km east-
this system (Figs. 23 and 24; P. B. Crean, Environ- ward from the Pacific Ocean to just west of Port
ment Canada, personal communication; Thom- Angeles. During two winters (February-May 1976
son, 1975). Fronts are found inclined to the cur- and November 1976-February 1977) and one
rent at all angles, but tend to parallel the ebb cur- summer (June-September 1977), an ex' tensive
rent which is stronger and has stronger lateral series of near-surface (upper 25 m) current and
shear. Plumes that were visible during ebb tide at temperature measurements and over-the-water
Admiralty Inlet, at Deception Pass, and at the wind measurements was made from surface moor-
mouths of some of the smaller rivers disappeared ings at three sites (A, B, and Q positioned longi-
during flood tides. Fronts parallel to strong cur- tudinally in the western Strait (Fig. 25). Only Site
rents appeared at the boundary of the Fraser C was occupied during the first winter. Each sur-
plume (especially during flood tide), at the en- face mooring contained from one to five vector-
trances to Haro and Rosario Straits, and in the averaging current meters (VACM's) suspended
western Strait of Juan de Fuca. The parallel fronts within the upper 25'm of the water column and
suggested strong cross-channel shear of the along- one tower-mounted vector-averaging wind re-
channel current, and the cross-channel fronts sug- corder (VAWR). The shallowest VACM was
gested a gentler sloshing back and forth of the generally placed at a depth of 4 m. More details
sediment-laden water. Separation of data accord- are discussed in Holbrook and Halpern (1978).
ing to wind direction showed little dependence of In addition, subsurface moorings were deployed
frontal siructure on wind. for about 40 days each during February-April
'the -separation of cross-channel fronts was up 1976, October-December 1976, and June-August
to 20 or 30 km. The tidal excursions estimated 1977, using Aanderaa current meters with tem-
were 31 km for, the ebb tide and 11 km for the perature and conductivity sensors (Fig. 25).

J
VANCOUVER ISLAND

@NJU4
SAt
18 3 rn ISLA D
q
30'_ ir . - . .. ;.
QZ
V.tCTORIA:
AL w
TA31 6,
*N, 5
CA
FLATTE
4,
NEAH - *M14 MITH
SAY S
RACE
-RK
2 A
:M
E
2
48-
10
@@RT
ANGELES
WASHINGTON

124o 123'

Figure 25. The Strait of Juan de Fuca, showing Sites A, B, and C and
associated subsurface moorings.

Various numbers of meters were used on each excess of 150 cm/sec during both winter and sum-
mooring. The shallowest placement of instru- mer and across-channel components up to about
ments was at about 15 m depth and the deepest 60 cm/sec (Fig. 26). The records were dominated
about 5 m off the bottom. During the first winter by a mixed tidal signal with semidiurnal and'
three subsurface moorings (N, M, and S), each diurnal constituents. These have been removed
with four current meters, were positioned across from the records by low-pass filtering for the re-
the Strait at Site C between Tongue Point and mainder of this study. The resultant low-fre-
Beechy Head. During the second winter five sub- quency along-channel velocity showed greater
surface moorings (2, 3, 4, 5, and 6) were moored variability during winter with amplitudes compar-
across the Strait at Site B north of Slip. Point. A able to the tidal currents and at times actually re-
sixth mooring (W) was located in mid-channel versed to flow up-channel. During summer the
near the mouth of the Strait at Site A off Neah low-frequency along-channel component was
Bay. Finally, during the summer three subsurface relatively steady and was not observed to reverse
moorings (N, M, and S) were deployed across the direction. The low-frequency across-channel com-
Strait at Site B off Slip Point, and two more (W ponents did not change greatly with season, ex-
and E) were deployed in mid-channel off Neah cept at Site A where there was a substantial
Bay at Site A and off Tongue Point at Site C. The across-channel seasonal variation (factor of two).
middle mooring was lost. More details of the sub- Although small compared to the along-channel
surface moorings are discussed in Cannon and currents, these low-frequency across-channel cur-
Laird (1978). rents must be considered an important process in
Numerous separate CTD (conductivity, tem- the movement of foreign substances shoreward.
perature, and depth) surveys of the region were Some details are given in the reports by Holbrook
made to extend the spatial coverage and to cali- and Halpern (1978) and by Cannon and Laird
brate the Aanderaa sensors. In addition, various (1978).
auxiliary data were collected to support the pri- Mean flow. The near-surface currents, when
mary measurements. Typically, river runoff was vector-averaged over the record length, were all
low during the winter experiments and high dur- directed seaward (Fig. 27). This is in qualitative
ing the surnmer experiment. agreement with the classical picture of outflowing,
Examples of the along-channel and across- near-surface estuarine circulation. The mean
channel components of hourly averaged 10-m cur- . along-channel component of currents at 4 m de-
rents at Site C showed along-channel velocities in creased seaward from Sites C to A, with greater

Figure 26. Along and across channel currents at 10 m at Site C during
winter and summer, showing hourly averages, low-pass filtered and
total-record average values. From Holbrook and Halpern (1978).

Figure 28. Along-channel total-record average currents (cm/sec)
through sections at Tongue Point (top) and Slip Point (middle and
bottom). From Cannon and Laird (1978).

Figure 27. Vector mean currents (cm/sec) at 4 m during winter and slightly from the middle to both sides. If real,
summer. From Holbrook and Halpern (1978). there were possible geostrophic effects associated
with the down-sloping level of no motion between
the south and middle moorings. The upslope from
the middle to the north mooring possibly indi-
longitudinal variability during winter. During cated effects of curvature in opposition to and
summer the magnitudes were greater. greater than the geostrophic effect. This section
Flow through the sections averaged over the was located at a position where the channel width
total records showed the esturarine characteristics undergoes a relatively abrupt change, all of which
of outflow in the surface waters and inflow in the occurs on the northern side of the Strait.
deeper waters (Fig. 28). At Site C the largest aver- Flow through the section at Site B was very
age seaward currents occurred nearer the surface similar in winter-spring 1973 at Pillar Point,
and in mid-channel, being somewhat symmetrical about 10 km to the east (Huggett et al., 1976). The
about the middle station. The largest averaged level of no-net-motion was at about 50 m on the
landward currents favored the northern side and south side and about 100 m on the north, similar
the deeper part of the channel. The level of no-net- to that shown by Herlinveaux (1954) at Pillar
motion was relatively flat, possibly sloping up Point. Landward flow occured in the deeper
water with the strongest currents on the southern
side, and seaward flow occured above the level of

no-net-motion with the strongest currents also ap- across the Site C section. Values were maximum in
pearing to occur on the southern side during sum- mid-channel and decreased toward the sides.
mer but in mid-channel during winter. This may There also was a decrease close to the bottom due
be the result of having only two moorings during to friction. The total variance in the records de-
summer. The recent Canadian observations in creased with depth at each mooring except during
spring showed some differences, however, in that summer when there was initially a slight increase
the level of no-net-motion was observed to rise to with depth followed by a decrease. Of particular
the surface before reaching the southern shore. It ihterest was that the near-surface variance at the
is possible that the no-motion level reached the subsurface mooring at Site C, as measured by the
surface south of our southern mooring. If this Aanderaa meter, was the same as measured by a
were so, then one might expect to find net land- VACM suspended from the nearby surface
ward flow (parallel to the coast locally) near the mooring.
southern shore of this part of the Strait during Low-frequency variance represented a signifi-
much of the winter and spring. The average cant percentage of the total along-channel
salinity across this section in summer showed iso- variance during winter. At Site A, near the mouth
halines sloping down to the north except near the of the Strait, 27% of the variance at 4 m occurred
bottom. However, there were large salinity varia- in this range. At Site C, the variance at 10 m was
tions (described below) during winter. 140% greater during the first winter experiment
than during the second winter. Some of this differ-
ence may 6e attributed to the greater meteoro-
Variations. The total variance of the current, logical forcing during the first winter as described
which is equal to twice the kinetic energy of the in Section 2.3. Low-frequency variance during
fluctuations, changed both seasonally and summer was much lower than in winter and was
spatially. At Site A, the winter variance was 76% amazingly uniform. More details are given in Hol-
greater than the summer variance. Most of this brook and Halpern and in Cannon and Laird.
difference was due to seasonal changes in the Although the along-channel component of
amount of low-frequency and diurnal energy. At variance accounted for 84%-92% of the total
Site C, there was less seasonal change, with winter variance, important across-channel fluctuations
variance exceeding summer variance by only 11 % also occurred. At Sites A and B during winter,
at 'the 4-m depth. Winter-to-winter differences in more than twice as much variance occurred in the
total variance were small. Variance decreased low-frequency band as in the combined tidal
with depth during both winter and summer. bands. However, at Site C the low-frequency
Tidal energy dominated the along-channel com- variance was less than half the tidal variance. In
ponent of variance, accounting for about the cross-channel direction the low-frequency rms
65%-90% of it. Tidal variance expressed as per- currents were much larger than the long-term
centage of total variance increased with depth averaged (total record) currents. For example,
near the surface during winter and summer, and during winter at Site B at 4 m depth, the subtidal
root mean square (rms) amplitudes' of the semi- rms amplitude was 13 cm/sec while the long-term
diurnal tidal currents decreased seaward from 47 mean was 1.6 cm/sec. Low-frequency fluctua-
cm/sec at Site C to 31 cm/sec at Site A with no tions, with time scales greater than 5 days, domi-
significant seasonal variation. During surnmer, nated cross-channel advective processes. At a
however, large longitudinal variations were ob- speed of 13 cm/sec, a distance equivalent to the
served in the diurnal tidal currents, with rms width of the western Strait may be traveled in less
amplitudes of 18 cm/sec at Site A increasing to 29 than two days. It is known from the drifter studies
cm/sec at Site C. Apparently, the diurnal tidal described in Section 3.1 that a significant percent-
current oscillations were not stationary and had age of drifters ended up on the beaches after
an important seasonal baroclinic component that several days.
may be related to the physical oceanography of
the Washington coast. Major fluctuations in the Winter wind forcing. During winter in the
diurnal energy band have been found during the western Strait, a major oceanographic feature not
course of summer upwelling off the Oregon coast previously described is the significant amount of
(Hayes and Halpern, 1976). current variance occurring at frequencies lower
Observations* from the subsurface moorings than the tidal frequencies. This low-frequency
showed that the standard deviation about the variance decreased with distance landward from
total-record average in the east-west direction was the Pacific and varied greatly from winter to win-
greater across the Site C section than across the ter, Descriptions of the two winters show the
Site B section by about 10 cm/sec. The cross-sec- general characteristics.
tion area is smaller at Site C than it is at Sites A During the first winter the variations of flow
and B, which also implies larger tidal currents through the Site C section were large, and a pro-

gressive vector diagram WVD) of the 16-m records N
showed two periods of inflow and two periods of
outflow at the south mooring (Fig. 29). Inflow SHERINGHAM
pr@
occurred from mooring deployment (February 26,
1976) to March 2 and from March 21 to 28.
BEECHY
3
HEAD
The second inflow started later and lasted

level. Flow reversed second at the north mooring
longer at the middle and north moorings at this 23
and last at the middle. Also, the PVD at the N
middle mooring was closely parallel to the axis of 25 -30
the Strait, but at the side moorings there were
across-channel components. These reversals from M
the normal outflow near the surface to inflow
were similar to those observed by Cannon et al. 19MAR 14 26FEB
S
(1972) at the mouth of the Strait. Here they oc-
curred about 90 km from the mouth, The implied 25
excursion during the second inflow at the south 6 APR 2 MAR
28 MAR
mooring was about 150 km, a distance from the TONGUE
mooring greater than that from the mouth of the PT. ANGELES .
Strait to the west, or to land toward the east. The PT
excursions at the middle and north moorings were
about 100 krn. These reversals appeared directly
related to storm winds along the coast which 0 @0 wo ISO 260 2i, 360 3W_ iE
raised the sea level sufficiently to reverse the pres- KILOMETERS
sure gradient contribution of the sea surface slope Figure 29. Progressive vector diagrams of 15-m flow across the Tongue
and which are shown in more detail below for the Point section during winter. From Cannon and Laird (1978). All
records start at the mooring locations on February 26, 1976. Scale for
second winter. There were two major periods of mooring M is double that shown. Coast is shown but the scale is only
persistent southerly winds measured at the mouth about 20 km from Beechy Head to Tongue Point. North is along the
of the Strait on Tatoosh Island that corresponded vertical axis.
with the. two flow reversals (Fig. 13). Southerly
winds on March 9-13 evidently were insufficient
to cause reversal of the flow. During the strongest
southerly coastal winds, westerly winds were ob- 1: @Z%7
@.l JUAN
served in the Strait near the northern end of the
48'
section at Race Rocks. The north-south compo- 30'
VICTORIA
nent of winds measured at Tatoosh Island ac-
counted for approximately 61% of the low-fre- 0 K
1A 0.

8
quency along-channel current variations at 10 in 6
at the Site C surface mooring.

The spatial effects of an intrusion can be seen
from the surface temperature and salinity distribu- 7.2 7.0
10. 15m TEMPERATURE
tions measured at the beginning of the observa
tions. Relatively fresher and warmer water was 48'
observed along the south side (Fig. 30). Near- 30' .... .... ..
surface water with temperature exceeding 70C and
with salinities less than 30'loo occupied a large
traction of the Strait and penetrated almost to the
mooring section. Flow was landward at the 15-
and 29-m depths at the south mooring and was 29.5 111 30.0
slightly seaward at 19 rn at the middle and north 3-.5---:
moorings. The higher salinity water presumably
has come from Haro Strait just east of Victoria. 15m SALINITY
This was opposite to the case occurring during 1 27 FES 76
more normal estuarine flow, when the lowest 30' 124-00' 30,
salinities were observed in water coming from Figure 30. Near-surfiice temperature ('Q and sahnity (0/co) foRowing
Haro Strait and highest surface salinities were on deployment of Tongue Point moorings. From Camon and Uird
the south side of each section. (1978).

S M N S M N
0
031
3

31.
32 i0o 32

Ui
-33 _-33
29 FEB 76 200 25 MAR

S M N S M N
0

E
@32
2
3
33 TZ
100
3
LJJ

14 MAR 200 5 APR

Figure 31. Daily average salinity across Tongue Point section. From
Cannon and Laird (1978). Dashed line is daily average zero-motion
level.

The salinity distributions across the section cm/sec occurred in all near-surface records.
(measured by the Aanderaa meters) also had dif- Visual correlations between currents measured at
ferent characteristics, depending on whether there 4, 10, and 15 m at Site A were remarkably high
was an intrusion or the more normal estuarine (Fig. 32). Visual correlation for currents at 4 rn at
flow (Fig. 31). During both intrusions (February Sites A, 13, and C, however, were much less strik-
29 and March 25, 1976) the freshest water was less ing. Approximately 55% of the along-channel
than 30'loo and occurred on the south side. The variance at Site C was linearly correlated with Site
3201oo isohaline was relatively flat at about 100 m. A, with C lagging A by 47 hours. The amplitudes
Above this level the isohalines tended to slope up of the correlated fluctuations at Site C were 57%
toward the north. The 3301oo isohaline was near of Site A. Five major reversals occurred at Site A
the bottom as was indicated on a longitudinal with maximum landward (along-channel) currents
STD section. During more normal estuarine flow of 25-55 cm/sec, lasting from 3-10 days, and ac-
(March 14 and April 5), the freshest water was counting for 35% of the observational period
about 3101oo and occurred on the north side. The (Fig. 33).
isohalines all sloped down toward the north. The Longitudinal sections of temperature, salinity,
3201oo isohalines occurred at much shallower and density made on November 5, 1976, just prior
depths with the 3301oo isohaline about 50-70 m to mooring deployments, showed a lens of warm
shallower. Hourly average salinity sections during (>110C), low-salinity (<31.75oloo) water located
flood tide at all meters resembled the daily aver- just west of Site A. Near-surface water tempera-
ages very closely both during intrusions and dur- tures eastward were fairly uniform, with values
ing the more normal estuarine flow. However, at generally less than 9"C. The temperature charac-
the end of ebb tide during part of the first intru- teristics of this less-dense lens were used as a tracer
14 M@@

sion, all water greater than 33'loo had moved sea- during periods of near-surface net landward cur-
ward. Near-surface distributions remained very rents (Fig. 34). Vertical lines drawn at times of
similar to the daily average. arrival of the warm water lens at Site A show that
During the second winter, low-frequency cur- the arrival of the front occurred within a tidal
rent fluctuations with amplitudes in excess of 50 'cycle of the major low-frequency current reversals

NOV 1976 DEC JAN 1977 FEB

Figure 32. Vector plats at 6-h intervals of low-pass filtered currents at 4,
10, and 15 m at Site A. From Holbrook and Halpern (1978).

(seaward to landward). During all the major re- was about what was required to transit the dis-
versals, the warm lens arrived several days later at tance between the moorings near Sites A and B in
Site C. The minor reversals on December 8, 1976, about three days. The freshest water and warmest
and January 4 and February 1, 1977, were not temperatures indicated by the daily averages oc-
strong enough to advect the lens front 65 km up- curred near the surface on the south side with the
channel to Site C. isolines sloping up toward the north. The deeper
The main intrusion and flow reversals had their isolines were relatively flat with 33% at about
maximum extents across the Site B section on 120 in and 8 deg.C at about 110 m. Highest salinities
November 18 (Fig. 35). Landward flow occurred were near bottom on the north side.
entirely across the surface, and seaward flow oc-
curred throughout the deeper water except at the More normal estuarine flow during an interval
bottom on the south side. The near-surface aver- of weak winds showed a level of no-net-motion
age daily speed of 14 cm/s at the middle mooring sloped down toward the north more steeply than

NO DEC JAN FEB
76 76 77 77

Figure 33. Along-channel components of low-pass filtered near-surface
currents and winds at Sites A, B, and C. From Holbrook and Halpern
(1978).

12-
11- 4m TEMPERATURE SITE C
10-
9-
8-
7__

12--
11- 4m TEMPERATURE SITE 6
10-
9-
8-
7
12- 4m TEMPERATURE /SITE A
11
10-
9-
8-
7 .......... ...... ........
60- J--\- /ebb
Uj
U) 0-
f lood
- 1W4m ALONG-STRAIT CURRENTS1 /SITE A 15
-605 10 15 20 25 30 .... 5 ... 10 15 20 25 30 5 10 15 20 25 30 5
NOV 1976 DEC JAN 1977 FEB

Figure 34. Hourly values of near-surface temperature at Sites A, B, and
C and low-pass filtered along-channel currents at Site A. From Hol- Slip I km San Simon
brook and Halpern (1978). Point 2 3 4 5 6 Point
0
.-10'
the total-record average, but its location in mid-
0-
channel was about the same. Maximum seaward
-10
IOU - 0
speeds were located farther north, and maximum =0: out
landward speeds remained near the south side. In 0
Isohalines and isotherms in the upper water sloped
down toward the north, and the freshest, warmest 200
water was near the surface on the north side as in 18 Nov. 1976
the first winter. Below about 100 m the isolines 0
sloped down toward the south. Isohalines of 33
and 32'loo were located considerably nearer the
surface and sloped more steeply than during the E
- 100
intrusion, which was also characteristic of the pre-
n 1 33-
vious winter. Strong easterly winds occurred in
late November-early December, the seaward flow
became greater and extended deeper on the north 200 Salinity
side, and the isohalines sloped more steeply than
during the no-wind observations. Temperatures 0
were almost uniform throughout the upper water,
and the highest salinities remained near bottom on
the north side.
:@z 100 -8-
Although the winds at Site A were consistently
directed seaward (positive) at 7 m/sec, the low-
frequency currents reversed from seaward to land- 200
_'V, r r
M r

'in

ward during the largest reversal, on November 14, Temp.
causing net landward advection. The temperature
front passed Site A during the middle of the tidal
flood on November 14 and returned during the Figure 35. Daily average along-channel currents, salinity, and tempera-
ture across the Slip Point section during the largest intrusion. From
following ebb (Fig. 34). After several days of Cannon and Laird (1978).

15 ALONG-STRAIT WINDS Z SITE 8 oqt- Strait
U.1
0, ki, V

in-strait
-15

20
15 BAKUN COMPUTED N-S COA TAIL W north
10
5
0
-5 V south
-10
60 ebb

0
__V
-60 IV' 4@ ALONG - S @TRAITCIIURRENTS /'SITE A flood
45
PRESSURE CORRECTED SEA SURFACE /NEAH BAY
30

15
0 '6 '' @S
5 10 15 20 25 30 5 10 15 2 30 5 10 15 20 25 30 5 10 15
NOV 1976 DEC JAN 1977 FEB

Figure 36. Along-channel and coastal winds, along-channel currents,
and sea-surface elevations showing various correlations. From Hol-
brook and Halpern (1978).

sloshing back and forth, the warm lens was winds off the coast and during increasing sea-
located far enough landward that short periods of surface height at Neah Bay. Significant correla-
tidal ebbs did not advect it seaward through Site tions were found: (1) between the along-channel
A. Although the along-channel components of 4-m currents at Site A and the north-south Pacific
winds,at Sites A, B, and C (Fig. 22) were strongly winds, with currents lagging winds by 42 hours;
correlated with each other, local wind forcing of (2) between the along-channel 4-m currents at Site
the near-surface currents was weak and only A and sea-surface height at Neah Bay, with cur-
barely significant. rents lagging sea-surface height by 6 hours; and
The wind-stress field off the Washington coast (3) between the north-south Pacific winds and sea-
can indirectly influence the along-channel currents surface height at Neah Bay, with sea-surface
through induced sea-surface height fluctuations. height lagging winds by 24 hours. Temporal de-
During winter, southerly winds may be expected celerations as large as 140 cm/sec in 4 days were
to pile up water along the coast through onshore observed at Site A (Fig. 34). A sea-surface slope of
Ekman transport. This increases the coastal sea- 4 cm/10 km would be necessary to balance such
surface elevation, which,in turn decreases the decelerations. Low-frequency sea-surface eleva-
longitudinal sea-surface slope in the Strait, cauS7 tion fluctuations of 15-20 cm. near the entrance
ing a deceleration of the seaward near-surface may be large enough to set up local 10-20-km
circulation. slopes, which travel slowly (30 cm/sec) eastward
During the second winter surface winds were as baroclinic waves@ The existence of the strong
computed for a 3 0-square pressure grid centered at local density gradient associated with the warm-
48'N, 125'W (25 km off the Washington coast) water lens would complicate such a picture. Re-
by rotating directions 15' counterclockwise and gardless of the coupling mechanism, strong co-
by reducing speeds by 30% to approximate the herence existed between the north-south Pacific
surface frictional effects (A. Bakun, NOAA, Na- winds and the low-frequency along-channel near-
tional Marine Fisheries Service, personal com- surface currents in the Strait. Winds measured
rv@ A, S

munication) (Fig. 36). Vertical lines were drawn at during the first winter at Tatoosh Island also sup-
times of maximum deceleration of the along- port this concept (Figs. 14 and 28).
channel currents when accompanying sea-surface The largest seaward flows at Site A tended to
height data existed at Neah Bay. Generally, de- parallel the axis of the Strait. During the mid-
celerations occurred during strong southerly November intrusion, the flow had a large south-

ward component at Site A (Fig. 32) and at Site B
(not shown). Presumably, this was the result of
southerly coastal winds forcing surface water up
against the Vancouver Island coast, creating large
secondary across-channel flows. Statistically, at SAN SIMON PT.
midchannel Sites A and B, across-channel flow
was correlated with along-channel flow, with in-
trusions having a south-shore transport and sea-
ward flow having a north-shore transport. Intru-
sions, on the south side of the Site B cross-section,
however, tended to parallel the shore line, while
seaward flow had more of an across-channel com-
ponent away from the shore (Fig. 37). There was
little evidence of shoreward flow at this location. - _@J/1@ AU
However, seaward flow at the northern mooring - N
showed a persistent shoreward component, but SLIP
the intrusion flowed parallel to the axis. This is PTI
significant because winter-feleased drifters tended PILLAR
to beach on Vancouver Island as shown above in PT.
Section 3.1. Summer observations (not shown) Figure 37. Vector plots of daily averages of low-pass filtered currents at
were less conclusive. Although there were inter- the 15-m level across the Slip Point section. From Cannon and Laird
vals of 2-3 days with shoreward components to (1978). Dots represent mooring locations.
the flow at the south and north moorings, there systems is accomplished principally by estuarine
were no extended intervals as shown at the north and wind-driven currents superimposed on the
mooring during winter. tidal currents. The importance of winter reversals
These intrusions of coastal water probably in- in the eastern Strait is unknown at this time, but
clude a mixture of Columbia River water, which is they may play a major role in the circulation and
known to flow northward along the Washington even dominate the local wind-driven near-surface
coast in winter (Barnes et al., 1972). Observations currents. The moored current meter data obtained
by Barnes et al. showed the plume extremely close by the National Ocean Survey (Section 2.2) were
to the coast during major storm periods. Predomi- intended primarily to define the tidal currents. Al-
nantly southerly winds tended to cause an onshore though the current records were relatively short (a
component of surface-water flow. Canadian in- month or less in duration) they can be used to
vestigators also have observed fresher water near make initial estimates of the longer period
the surface on the southern side of the Strait of estuarine and wind-driven currents without regard
Juan de Fuca during similar winter storm condi- for seasons. No summer observations were made.
tions (Crean and Ages, 1971). The flow reversals A new PMEL current observation program is
have been observed across the entire continental measuring currents in the eastern Strait for 1978.
shelf in the glacial trough which cuts the shelf The data are not available for this report, but will
(Cannon et al., 1972), and Canadian investigators be available about one year after the study ends.
recently have shown PVDs with similar reversals The mean surface currents for the eastern Strait
near Pillar Point (Hugget et al., 1976). Drifter of Juan de Fuca and for the region in and around
studies on the continental shelf also have indicated the San Juan Archipelago were calculated for the
winter northward flow along the coast. Some drift total, but varying, record lengths (Figs. 38 and
bottles released during the winters of 1960-63 near 39). The data were scattered in time so that they
and south of the latitude of the Columbia River do not give an instantaneous picture of the mean
have been recovered in the Strait of Juan de Fuca flow. Instead, they are suggestive of the magni-
(Burt and Wyatt, 1964). A few were recovered tude and direction of the currents with periods
east of Port Angeles. Some bottom drifters re- longer than those of tidal currents and of the
leased along the coast also have been recovered in variations in the magnitude with location. The
the Strait, but these are not necessarily indications numbers beside the current vectors are related to
of the surface intrusions (Barnes et al., 1972). standard deviations of the components and are
measures of the reliability of the mean current vec-
3.4 Eastern Strait-San Juan tors. A number much less than one indicates 1hat
_N SIMON P
1411 @4@1

the scatter of the individual currents, which were
Island Currents sampled every six hours after the tidal currents
had been removed, was relatively small and
The transport of water and material between demonstrates that the mean current was relatively
the Strait of Juan de Fuca and the Strait of Georgia steady during the period of observation. Numbers

VANCOUVER ISLAND

1,07

1,29
.50
.24 94
.60
. ........ ... 109
25
36
.oc
.24 /T Z
1,27
.70
;,5 .26 @35
J
13
3 '18
'61 .95
23 .10
.50
..... ... ......... . . .....

6
MEAN
@62/
CURRENTS
22
20 c ms
... 10 fathom Curve WASHINGTON

Figure 38. Near-surface mean currents observed during spring and fall
in the Strait of Juan de Fuca. Prepared for this report by Mofield.
Numbers near the current vectors indicate the scatter in the long
period currents.

MEAN
CURRENTS
0 20cm/s
..... 10fathom curve

FSE N DE R
SAT RNA 1.

is.
91
46
EuM I
41
ON

%
SLAND
ORCAS I
35@

DR
C
SHAW
Y

SAN JUAN
ISLAND
ANACORT

C3
LOPES

.20

viCTORIA

Figure 39. Near-surface mean currents near the San Juan Archipelago.
Prepared for this report by Mofjeld.

equal to or greater than one indicate that the long- data have verified, however, that the deeper,
period currents varied considerably and that the long-period motions tend to be opposed in direc-
mean therefore was not representative of the non- tion to the near-shore surface flow, which is con-
tidal current at those locations. The variability sistent with estuarine flow.
was due in large part to fluctuations in the wind- Similar calculations were made for the mean
driven currents. However, no wind records were current vectors for the region immediately north
available for the varying times of observation. of the San Juan Islands in the southern Strait of
Small variability probably indicated that the long- Georgia and in the immediate vicinity of Cherry
period flow was controlled by the estuarine cir- Point (Schumacher et al., 1978; Tracy, 1975).
culation, although rectification of tidal currents in Mean flow during late winter-early spring 1975 on
near-shore eddies also produces a local mean cur- the western side of the southern Strait of Georgia
rent observed by a moored current meter. Several was found to be predominantly driven by Fraser
of the large mean currents directed toward the River discharge (Fig. 40). River water crossed the
beach at near-shore locations are thus suspect. Strait and proceeded along its western side in a
Most of the largest mean currents were observed southeasterly direction. Bathymetry north of
in the more confined passages. The vertical dis- Boundary Pass (between Saturna and Patos
tribution of the long-period currents in the system Islands) caused a portion of the less saline surface
are not defined with precision by the NOS data waters to bifurcate, with one portion flowing east-
because of the limited number of meters deployed ward and southeastward along the San Juan
on each mooring to measure tidal currents. The Archipelago and the remainder flowing seaward-

123 20' 123 00' 122 40'
49 00' 49 00'
PT
100 fms ROBERTS CURRENT METER STATIONS
0 5 10 20 30 NET SURFACE FLOW(5 m)
NET MID-DEPTH FLOW(21 m)
SPEED SCALE NET BOTTOM FLOW
(cm/sec') 58 INFERRED FLOW
REGIONS INDICATING FRASER
RIVER WATER

through Haro Strait. Oceanic water entered the Little work is currently available describing
system flowing landward at depth through Haro flow in the passages between the San Juan Islands,
Strait (the deepest connection with the sea) in re- and that which is available is of short duration.
sponse to the fresh-water runoff. A two-layered Drogue observations made in various places along
flow regime also was observed in the Strait of Rosario Strait for durations of 1/2-1 day showed
Georgia across the section from Point Roberts to no groundings of the drogues except for a few re-
Mayne Island. On the shallower eastern side of the leased very near to shore (Schumacher and
Strait of Georgia, surface waters showed a weaker Reynolds, 1975). Current observations in the
mean current flowing northwestward, and the southern half of Haro Strait showed two-layered
water- column was well-mixed. There was little or flow with the depth of no-net-motion at about
no evidence of mean northward flow through 50 rn near the junction with the Strait of Juan
Rosario Strait. This work and the satellite �tudies de Fuca and deepening northward to about 100 m
of the Fraser River plume are mutually supportive. (D. Evans and E. E. Collias, University of Wash-
The indications of Fraser River water in this study ington, unpublished manuscript). The no-motion
(Fig. 40) are the same as shown previously for ebb layer sloped across channel and upward toward
flow partly exiting into Haro Strait (Fig. 19). the east, or to the left looking seaward. Cross-
It has beenreported that in the southern Strait channel surface flow was observed near periods of
of Georgia the flooding tidal current was stronger slack water, a phenomenon which is common to
and of longer duration than the ebb on the eastern many of the more restricted passages. Some recent
side. The opposite existed for the western side, Canadian work in Haro Strait is noted below in
and this tidal inequality tended to drive the ob- Section 5.
served counterclockwise circulation (Waldichuck,
1957). However, more recent data have indicated
no net flow northward through Rosario Strait 3.5 Plankton Observations
(Schumacher and Reynolds, 1975). These two
studies suggest that the apparent tidal inequality Cruises were made in the Strait of Juan de Fuca
results from superimposition of tidal current upon for over a year during 1976-77 to determine sea-
mean estuarine flow. sonal distributions of plankton. The sporadic oc-
The wind field during this study was relatively currence of a group of coastal surface-living
uniform over the entire area; topography con- plankton species was unexpected in view of the
quasi-constant surface outflow (Table 1).
trolled the flow, Which resulted in axial winds Initially, the zooplankton species were believed to
Strong estuarine flow on the western side reduced be deep strays entering the Strait at depth. How-
the impact of wind-induced movement, and thus ever, these zooplankters were not seen in deep
there was little direct correlation between mean samples, and they were not found in summer,
flow and winds. On the eastern side of the Strait when they can be very abundant offshore.
near Cherry Point, winds played a more dominant In November 1975 a large bloom of phyto-
role in driving the circulation, and a relatively plankton occurred off Neah Bay together with
high correlation coefficient existed between axial typical offshore phytoplankton and zooplankton
winds and currents. During periods when winds species. Physical oceanographic observations
exceeded 10 m/sec, approximately 71% of the independently taken at that time revealed an in-
variation in the mean current velocity was ac- trusion of relatively warm coastal water into the
counted for by a linear relationship with axial western Strait. During two cruises in 1977 there
winds, and axial current speeds were approxi- were no independent physical data to support the'
mately I% of axial wind speeds. occurrence of some of these coastal species. But at
The southern Strait of Georgia encompasses a all other times these coastal species were only
relatively small area. However, its geomorphol- found in the Strait in association with or very
ogy divides this small area further into two dis- close to incidents of documented coastal water in-
tinct subregions. Circulation response to local trusion and current, reversals from seaward to
forcing mechanisms in each of these subregions is landward flow. The correlation is excellent.
substantially different. The western half is domi- These plankton species could act as indicators
nated by gravitationally convected estuarine cir- for surface coastal water, which at times might in-
culation, while the eastern half responds almost fluence even the easternmost limits of the Strait.
solely to wind-forcing. Some recent Canadian Also the distribution of deep-water plankton is
studies have examined various aspects of flow in limited within the Strait system by the presence of
the Strait of Georgia in considerably more detail the various sills. More details of this work are dis-
(Chang et aL, 1976; Tabata, 1972; Crean, 1978). cussed in Damkaer and Larrance (1978).

cp > z a 0 0 z
eD (D a 0 rD eD rm
M M M 0 m eb
n n n
t@ al (.n tj
tj rm
ol Ul,
1 00
w Cn
(n (D 00 00 10 >

0 1> -2) z >
t3 0 C: "a rD
'D GQ U,
t'j U, w
U, (7
i@n w W I t'@ rm
0, - Un
Ul 00

Calanus
tenuicorni

Clausocal
lividus
Clausocal
paraperge
Calocalan
styliremis
Acartia
danae

Phronima
sedentaria
Dictyocys
reticulat

Parafavell
gigantea
Radiolaria

Coccolith

Bacteriast
delicatulu
Asteromp
heptactis
Rhizosole
alata

Chaetoccr
convolutu

4. OIL-SPILL TRAJECTORY MODELING

4.1 Model Description

An oil-spill-trajectory computer moder consists Models increase in complexity from this point. In
of three basic components. The first is a collection the present study, for example, the time behavior
of tables and/or numerical formulas that specify of the current has been simulated by using locally
the time and spatial behavior of wind and current. measured tidal amplitude and phase data for the
These tables represent the movement and mixing five most significant tidal harmonics. The spatial
of ocean and coastal waters at some nominal reso- behavior of the current was interpolated between
lution independent of the possibility of an added measurement points using hand-derived coeffi-
pollutant. The second component is a motion cients. The spatial behavior of the wind field was
equation that relates the movement of a central deduced by using a combination of local measure-
element of an oil spill, treated as a particle, to the ments and the results of the numerical model dis-
specified local wind and current. The third com- cussed in Section 2.3 that accounted for the effects
ponent is a set of quantitative relations that of the local topography and air stability.
specify the spreading, sedimentation, and Because the equation of motion is empirical and
weathering of the oil following a trajectory path. based on only a few observations,- there currently
The latter clearly depends upon the physical and is little knowledge of the errors inherent in any
chemical characteristics of the oil as well as envi- particular calculation of spill motion. Without a
ronmental conddions. The results to follow have knowledge of these errors, it is not possible to esti-
neglected those factors which depend upon the mate quantitatively the effects of errors in the
volume and type of oil and have concentrated specification of the wind and current fields on the
simply upon trajectory plots of idealized particles spill trajectory, because the trajectory and the
advected by currents and drifted by the wind. driving forces are coupled by these poorly under-
All oil-spill trajectory models are essentially the stood equations. However, some conclusions are
same with respect to the motion equation. They still possible regarding the properties that should
rely on empirical and uncertain relationships that be built into the wind and current simulations, ir-
link oil-spill velocity with the vector sum of the respective of the spill motion model. Of prime im-
local current velocity and a fraction, e.g., 3%, of portance is the proper simulation of the evolution
the wind velocity. Such estimates are obtained of the-winds and currents in time. In this regard,
from after-the-fact analysis of the trajectories of the ebb and flood phases of the tides are obviously
major oil slicks. Drift factors represent an ap- important, but so is the persistence of the wind.
proximate composite response for the complicated Most winds only remain in a given octant for a
interaction between wind, waves, oil, and water. few hours, and the changes after that are funda-
Comparison of observed and predicted trajec- mentally random, although they may exhibit cer-
tain patterns. The reason this time-wise evolution
tories for the grounding of the Torrey Canyon is important is that the assessment of oil-spill risk
showed daily variability of drift factors of from a location requires that the ensemble of all
2.5%-4.5% for best fit. For the cases shown here possible spill scenarios be examined. Spills can
particles were advected with the velocity of the happen at all phases of the tide and in all wind
tidal current plus 3.5% of the wind speed in the conditions. Each initial condition will result in a
direction toward which the wind is blowing. collection of trajectory possibilities consistent
The method of handling the wind and current with the temporal evolution of the wind and cur-
data largely distirtguishes one model from an- rent fields from the initial state. It is this time-wise
other. The crudest models assume spatially uni- behavior that will determine which beaches are
form and time-steady currents or winds, or both. most likely to be impacted.

An algorithm to simulate the tidal currents in Island. These local wind patterns were estimated
the Straits of Juan de Fuca, Georgia (U.S. part), from observations for each synoptic case supple-
Rosario, Haro, and in other connected channels mented by subjective guidance provided by the re-
and bays was written for use with the oil-spill gional meteorological model described in Sec-
trajectory model. The principal purpose of this tion 2.3. To date and for this report, two local
algorithm was to furnish components of the tidal wind fields have been completed, corresponding
velocity when interrogated with appropriate in- to the more persistent cases of east and west winds
formation about position and time. The two (Fig. 41). An important omission is the short-
major sources of tidal current information were 57 duration storm situation with strong southerly
stations from NOAA/National Ocean Survey winds in the eastern Strait and light winds at Port
(1976), in conjunction with the NOS standard har- Angeles in the lee of the Olympic Mountains.
monic constants for the prediction of currents at
six primary stations, and 90 stations from Parker
(1977) with standard harmonic constants for each 4.2 Sample Trajectories
station. Stations from Parker were considered the
primary data set, with NOS tidal tables supplying The unity of the oil-spill trajectory model stems
information primarily in the secondary channels. from its ability to incorporate wind and current
The computations were carried out using a one- fields that are variable in both time and space.
kilometer grid over the entire region of interest. Tidal currents are nearly periodic in time at a
Each square in the grid was assigned a sequence given location over the period of several days but
number related to the current configuration in. that can change magnitude and direction over short
square. Several neighboring squares might have spatial distances. The wind field varies signifi-
similar currents and all have the same sequence cantly in both time and space. The trajectory
number. The groupings varied in size from groups model provides a testing ground for determining
of one or two squares in small channels to groups the importance of these features to the oil-spill
of 80 or more in areas of less complicated flows. motion problem. This section discusses three ex-
Each sequence number was assigned a direction of periments with the trajectory model. The first two
flow at flood current, and up to three NOS sta- specify winds constant in time corresponding to
tions were used to interpolate the current and the the east and west wind fields outlined in the pre-
respective proportionality fractions of their influ- vious section. The third specifies time-varying but
ence. The direction of ebb was assumed to be spatially uniform winds for a release site near Port
opposite that of flood. Angeles. Five release sites in the eastern Strait of
The currents at the reference stations were cal- Juan de Fuca were used in the first two cases
culated by the numerical harmonic method de- (Fig. 42). Sites a, b, and e correspond to intersec@
scribed in U.S. Coast and Geodetic Survey (1958). tions in the vessel traffic-control system, while
The five largest contributing tidal constituents, Sites c and d are the entrances to major shipping
M, S, N, K, and 0, were used. routes through Rosario and Haro Straits.
The routines were tested in parts and as a Figure 42 shows the plotted trajectories for
module in the trajectory model. A test run was easterly winds in the Strait (Fig. 41) keyed to a
made for March 1976 off Port Angeles. The wind magnitude at Tatoosh Island of 10 m/sec.
diurnal inequality was well represented in the re- Crosses on trajectories are at 24-h intervals. Start
sults, and the phasing matched the predicted time for the current field was noon on March 15,
values in the NOS tables. While a mean drift is 1976. Trajectories a and b were under the influ-
specified for each station from the tidal analysis, it ence of strong winds at the outer end of the Strait.
represents a climatological mean value of non- Drift toward the west was on the order of 10
tidal drift over the period recorded by each instru- km/day. The release in Haro Strait (Site c)
ment. The model, therefore, does not include the traveled south under the influence of the cold air
instantaneous effects of non-tidal drift such as ex- winds from the north. It reached the central Strait
tremes in the estuarine flow described above in far enough west that the trajectory continued west
several sections. under the influence of the gap winds in the central-
The procedure for providing spatially de- western part of the Strait. The release in Rosario
pendent winds to the trajectory model was to Strait (Site d) was blown south similarly to that at
specify two keying parameters, the direction and Site c but approached a region of lighter winds in
wind speed measured at Tatoosh Island at the the vicinity of Site e, where the response was pri-
entrance to the Strait of Juan de Fuca. Amplitude marily tidal.
ratios and local directions were estimated for a For time-invariant winds from the west
fou'r-kilometer-square grid overlying the region to (Fig. 41), the same five release sites have been
convert the keying parameters to local winds for simulated (Fig. 43). The keying wind magnitude is
each 45' segment of wind direction at Tatoosh again 10 m/sec, and the currents were initialized

4-4-

-4

Figure 41. Local wind field for offshore winds from the west (top) and
east (bottom). Relative wind speed is scaled by the length of the
arrow.

at noon on March 26, 1976. Trajectories starting Islands. West winds in this part of the Strait of
west of Port Angeles (Sites a and b) traveled east Juan de Fuca diverge on a line running due east of
at a rate of 10-15 km/day, separating with a Race Rocks, blowing toward the San Juan Islands
diverging current pattern at the east end of the above this line and toward Admiralty Inlet and
Strait. Landfall occurred in five days, which is Whidbey Island south of this line. The trajectories
much longer than west winds can be expected to reflect this behavior.
persist. Releases from points at the eastern sites (c, Figures 44 through 46 show 24-, 48-, and 72-
d, and e) quickly reached landfall in the San Juan hour trajectories for a release site southwest of

124.0.Ow 122.35.Ow
48.30.On

C d

-48.0.On

Figure 42. Trajectories from five release sites during easterly winds.
Crosses (X) represent twenty-four hours of travel time. Stars (*) rep-
resent landfall or termination at five days.

Race Rocks with six releases at 1200 PST on sults both from the strong channeling effect of the
March 12, 15, 18, 21, 24, and 27, 1976. The wind Strait on the tide and the east-west orientation of
was assumed uniform over the region, and the the wind in the vicinity of Race Rocks. This is
time variations were based on hourly wind obser- something of an artifact because of the spatially
vations made at Race Rocks in March 1976. Due uniform wind field assumption. Based on Figs. 42
to the known spatial variability in the wind field, and 43, some northward component in the trajec-
these trajectories can only be trusted while they re- tories can be expected once they get as far east as
main in the vicinity of Race Rocks. For purposes New Dungeness and as far north as Race Rocks.
here, "vicinity" was loosely interpreted as mean- The two spills that traveled into Admiralty Inlet
ing west of New Dungeness and south of Race both spent some time in this region, and some
Rocks. During a typical March the average wind is north-south perturbations might have been ex-
from the west in the Strait of Juan de Fuca, so pected. Spills with a net westward transport also
spills should be expected to have predominantly could be expected to have some northward com-
eastward trajectories subject to tidal currents and ponent once they were beyond the lee of the
the local wind. This behavior is reflected in all Olympic Mountains.
three figures. After 24 hours, two spills had There are several qualifications that should be
traveled 15 km to the east, three spills had emphasized regarding these trajectories. First,
traveled about 5 km to the east, and only one spill they are not intended to be an exhaustive sampling
showed a net transport to the west (Fig. 44). After of all the trajectory possibilities. They are simply
48 hours, four spills were clustered in the region six trajectories from a typical March. If six trajec-
northwest of Admiralty Inlet, one spill returned to tories had been drawn from March of 1977, which
the vicinity of the launch site south of Race Rocks, was atypical, the predominant transport would
and the last spill still showed a net westward have been to the west, not to the east. No attempt
movement (Fig. 45). Finally, after 72 hours, two has been made to present a spectrum of results
spills were as far east as Admiralty Inlet, two spills that would have indicated this potential for vari-
were between New Dungeness and the launch site, ability. Second, only wind and tidal currents have
and two spills were 3-5 km west of the launch site been considered. Besides these, there are strong
(Fig. 46). Because of the assumption of a spatially low-frequency currents associated with wind
uniform wind field, the location of the spills setup along the coast and with fresh water runoff,
farthest east must be considered questionable but as described in various parts of Section 3. These
nevertheless suggestive. are not included in the current field. Transport
A prominent feature of all three figures is the from these currents could easily overwhelm a rela-
east-west orientation of the trajectories. This re- tively weak wind transport. Unfortunately, these

124.0.Ow 122.35.0-Ow
11 -48.30.0 n

Port Angeles

__48.0.0n

Figure 43. Trajectories for five days during westerly winds.
124.0.0 w 122.35 1Ow
11-48.30.On

Port Angeles

48.0.On

Figure 44. Trajectories for six releases at site northwest of Port Angeles.
The releases were at three-day intervals starting at noon on March
15, 1976. Each trajectory is based upon hourly winds at Race Rocks
initialized on the six days. Each trajectory is for twenty-four hours.

currents are not yet sufficiently understood to be strong dispersion evident in the drift card trajec-
modeled. Third, no explicit consideration was tories shown in Section 3.1. Finally, no considera-
given the effect of storm passage on spills in the tion was given to summer cases, which are charac-
eastern strait region. Within several days of a re- terized by persistent high pressure offshore, result-
lease, a frontal passage could be expected, chan- ing in predominantly west winds modified by
neling strong southerly winds through Puget diurnal sea breeze. Further work, including the
Sound. Such events may be responsible for the summer examples, is underway in the numerical

124.0.Ow 122.35.Ow
4J k-48.30.On

Port Angeles

-48.0.On

Figure 45. Trajectories after 48 hours for releases shown in Fig. 44.

124.0.Ow 122.35.Ow

Its

Port An(
,jeles

-48.0.On

Figure 46. Trajectories after 72 hours for releases shown in Fig. 44.

studies group at PMEL, and the results should be
available in a separate report late in 1978. Results
to date from their ongoing study have been de-
scribed here.

5. OTHER STUDIES

Canadian investigators conducted a number of the bottom. The principal semidiurnal component
studies in the western Strait of Juan de Fuca in the M, changed very little near the cross-section,
vicinity of Pillar Point during 1973 and 1975 and averaging around 48 cm/sec with a phase angle of
in the southern part of Haro Strait northwest of 245'. Similarly, K, averaged 29 cm/sec with a
Victoria during 1976. Results from these studies phase angle of 2540. The residual currents showed
are beginning to be published, and brief sum- a seaward or westward current in the upper por-
maries from their reports follow. These are part of tion of the Strait and a landward or eastward cur-
ongoing studies, and the results should be con- rent in the lower half. The line of null velocity
sidered preliminary until completed by the respec- sloped upward from around a depth of 110 m on
tive scientists. Recent Canadian work in the Strait the north side of the Strait to the surface on the
of Georgia was noted in Section 3.4. Also, the southern side about one-half mile offshore. The
tidal modeling work in the Strait of Juan de two layers had the same maximum speed (around
Fuca-Strait of Georgia system is a continuing en- 14.5 cm/sec) with the maximum seaward current
deavor, and the most up-to-date descriptions are being on the surface in the center of the Strait and
in Crean (1978). PMEL trajectory modeling will be the maximum landward current centered about
continued this year as outlined in Section 4, and the middle of the lower layer. The close similarity
further results will be in a future modeling report. of our overall averages was indicated in Sec-
Major field investigations in 1978 are underway in tion 3.3. Also, reversals were observed in their
the eastern Strait of Juan de Fuca because of a lack current records, but no attempt was made to cor-
of information about this area. This is a joint in- relate them with storms or wind events. A signifi-
vestigation between PMEL and the Institute of cant finding is the possibility of net eastward flow
Ocean Sciences, Environment Canada, and a brief at all depths near the southern shore at this time of
summary of the study follows. Preliminary results year at this location.
for the eastern Strait work are planned for sum- The 1975 Canadian observations of currents,
mer 1979 as a supplement to this report. bottom pressures, and various auxiliary data were
The 1973 Canadian oceanographic program in obtained in the Strait of Juan de Fuca from May to
the Strait of Juan de Fuca was both an investiga- July. The primary purpose of these measurements
tion into the flushing process of the Strait of was to investigate the relationship between the
Georgia and an attempt to obtain current observa- currents flowing along the Strait and the differ-
tions as input to the Strait of Georgia numerical ence in bottom pressures across the Strait. A close
tidal model. Continuous records of currents (and correspondence between these two quantities
temperature and conductivity at some locations) would provide a method for computing the cur-
were obtained for three months, and at two sta- rents from pressure measurements made on oppo-
tions for over five months, all commencing in site sides of the Strait (Fissel and Huggett, 1976;
March (Huggett et al., 1976). Time series of tem- Fissel, 1976).
perature and salinity profiles were taken at a num-
ber of stations during the time the current meters The Canadian group calculated currents from
were in place and at a few stations from June to these differences of pressure, which generally
December when there were no current ob- agreed within 20% with the measured current.
servations. Errors in the method were determined to be due to
Their data showed current speeds from just physical phenomena which also caused differences
under 125 cm/sec on the surface to 75 cm/sec near in the pressure across the Strait. These phenomena

were thought to be local accelerations of the cross- occurrence of spring tides, the maximum north-
channel current and variations in the density on ward flowing tidal current was associated with the
either side that were not in isostatic balance with appearance of a 250-m-thick layer of almost uni-
the sea-surface elevation. Thus, for the full signal form salinity in the southern end of Haro Strait.
the accuracy of the pressure difference method The 1978 PMEL program in the eastern Strait of
will depend largely on the size of these other fac- Juan de Fuca consists of two separate experiments,
tors relative to the pressure differences resulting one in winter (December 1977-April 1978) and
from the Coriolis force. The method could not be one in summer (July-September 1978), utilizing
tested properly for residual currents, because large moored current meter arrays, surface wind, sen-
spatial variations of residual current fluctuations sors, and CTD data. Supporting meteorological
across the Strait indicated that sampling the cur- and circulation data will be obtained from, NWS,
rent at five locations was not adequate to compute NOS, FNWC, and Environment Canada. Three
a meaningful cross-channel averaged residual cur- surface and three subsurface moorings will be
rent. However, correlation with the pressure dif- positioned as centrally as possible in the main
ferences was surprisingly good. channels connecting the eastern Strait with the
The 1976 Canadian study in Haro Strait was western Strait, Haro Strait, and Admiralty Inlet.
conducted from July to September to determine A triangular configuration of these arrays will be
some of the major water characteristics and flow used to describe flow. Additional subsurface
in that region for late summer. The study included moorings will be placed near the Admiralty Inlet
observations of currents across a section, tempera- sill and farther west at the same locations occupied
tures using thermistor chains, several time series during the program in the western Strait described
of CTD profiles over 25 hours, and winds (D. M. in Sections 2.2 and 3.3. At the same time, Cana-
Farmer, Environment Canada, personal com- dian scientists will place several moorings near the
munication; Webster, 1977). north end of Haro Strait in the Strait of Georgia.
This study showed estuarine circulation, and Winds measured at the surface moorings will be
the level between inflow and outflow was ob- supplemented by wind measurements from ane-
served to vary between 40 and 100 m on the east- mometers located on Smith Island, Tatoosh
ern side to greater than 100 m on the western side. Island, New Dungeness spit, and from the weather
Deepening to the west was similar to that noted in station at Port Angeles on Ediz Hook. Tidal
Section 3.4. Following spring tides, the velocity, heights will be available from NOS tide gauges at
temperature, and salinity gradients were found to Neah Bay, Port Angeles, and Port Townsend.
be minimums, and following neap tides they were CTD sampling of the entire Strait of Juan de Fuca
maximums. Tidal phases were smallest in the sur- including the Admiralty Inlet sill region will be
face on the eastern side. Phases increased with done during deployment and recovery of the
depth and towards the western side. Pronounced moored arrays and once about midway. Other ob-
changes occurred in the water characteristics in servations of surface flow on a broader scale may
the whole water column of Haro Strait over take place at short intervals during the summer
periods of a day. For example, coinciding with the deployment.

6. SUMMARY AND CONCLUSIONS

The Strait of Juan de Fuca estuary is a major of the San Juan Islands and in Admiralty Inlet, ex-
shipping route for both the United States and ceeding 4-5 knots in some places. In addition,
Canada. The most recent published oceano- tidal currents away from shorelines can mix and
graphic description of this estuary is now over fif- disperse floating and suspended material, but they
teen years old, and much new work has since tend to produce concentrations in near-shore
taken place. Recently, the Pacific Marine Environ- eddies and at tidal fronts. Satellite photographs
mental Laboratory (PMEL) has been studying have shown large numbers of tidal fronts, particu-
near-surface circulation and its driving mecha- larly on either side of the San Juan Islands (Figs. 23
nisms and has been developing a computer model and 24). Studies in the Puget Sound laboratory
to predict possible trajectories of spilled oil. The hydraulic model at the University of Washington
National Ocean Survey of NOAA has been have shown, in the vicinity of Admiralty Inlet (the
measuring tides and tidal currents in order to pro- northern limit of the model), the existence of near-
vide improved predictions. Environment Canada shore eddies almost everywhere on the down-
also has been investigating various circulation current side of points-of-land and in some embay-
problems in these waters and has been developing ments (Fig. 7). Canadian numerical tidal model
a numerical tidal model. This report summarizes studies also have shown similar eddies in the Strait
some of the results to date. of Juan de Fuca, and they probably exist through-
Because of potentially increased tanker traffic in out these waters. Tidal currents appear much
these waters, this synthesis of ongoing environ- more sensitive than tidal elevations (the rise and
mental studies has been written so that the most fall of the sea surface) to local variations in water
recent results will be readily available for use in depth and details of the shore line. This zone very
decisions regarding these waters. The primary em- close to shore has had very little study.
phasis of these studies has been either directly or Superimposed on the tidal motions are the
indirectly on transport mechanisms that might estuarine (river discharge) and wind-driven cur-
affect the redistribution of spilled oil. The primary rents which transport floating and suspended
questions that the studies have been attempting to material through the system or toward the shores.
Studies of these motions have been carried out at
answer are: Given an oil spill at some location in PMEL using, for example, surface drift cards (Sec-
the Strait of Juan de Fuca or near the San Juan tion 3.1), satellite photographs of suspended sedi-
Islands, what would tidal currents, river dis- ment (Section 3.2), moored current meters for ex-
charges, and wind-driven currents do to the oil? tended durations (Sections 3.3 and 3.4), and an
Would it come ashore, and if so where, or would oil-spill trajectory model (Section 4).
it be transported out to sea and away from the Drift cards released during spring and summer
shorelines7 No attempt has been made yet to relate south of San Juan Island in the middle of the east-
these results to specific ecosystems in the Strait. ern basin of the Strait have been found on all
More details will become available, especially for beaches surrounding the eastern basin (Fig. 18).
the waters east of Port Angeles, about one year Cards released in Puget Sound flowed out Ad-
after completion of the 1978 field studies. miralty Inlet and were similarly dispersed around
It is well known that tidal currents dominate the the eastern basin. Cards released closer to the
water motion in this estuarine system. The tidal southern shore throughout the Strait moved sea-
currents are navigational hazards because the cur- ward and were found primarily on the southern
rents are quite large in the more restricted passages shore. Drifters that were tracked during several

days in summer in the vicinity of Slip Point to mined by moored current meters and by observa-
Pillar Point showed flow parallel to the shore dur- tions of water properties showed patterns similar
ing ebb currents and toward the shore during to the Fraser plume (Fig. 40). Many of the plumes
flood currents. Cards released in winter were were very close to shore.
found mostly on Vancouver Island (Fig. 18). Sum- Moored current-meter observations in the west-
mer recoveries on the southern shore and winter ern basin of the Strait showed that the near-
recoveries on the northern shore of the western surface currents averaged over long times were
basin of the Strait were consistent with the con- seaward (or westward). During summer shorter-
cept of current drift to the right of prevailing term averages yielded seaward flow. However,
winds. Westerly winds dominated in summer, and during winter considerable variability was ob-
easterly winds dominated in winter. Also, moored served, and there were extended periods of 3-10
current-meter observations in winter showed sea- days when the averaged near-surface flow was
ward flow with a persistent shoreward component directed landward (or eastward). One month's ob-
near the coast of Vancouver Island (Fig. 37). Ob- servations across the Strait at Tongue Point
servations in summer were not as close to the showed two periods of inflow and two periods of
southern shore, and flow towards that shore was outflow on the southern side (Fig. 28). During the
observed only during relatively short intervals. second interval of inflow, the eastward-directed
Satellite observations of suspended sediment surface flow extended entirely across this section,
were most useful north of the San Juan Islands in and significant changes in the deeper flow also
summer when. sediment concentrations were were observed. In another winter five major flow
largest because of the nearness of the Fraser River reversals occurred, accounting for 35% of the ob-
and its large volume of sediment-laden river run- servation interval (Fig. 33). These flow reversals
off. Mixing in the San Juan Island passages con- were accompanied by intrusions of coastal oceanic
siderably reduced the sediment concentrations in waters which were relatively fresher and warmer
the near-surface water. Sediment plumes and (Fig. 30) and which contained coastal species of
eddies were observed where the Fraser first enters both phytoplankton and zooplankton (Table 1).
the Strait of Georgia. The plumes moved seaward The intrusions probably were mixtures of
primarily along the western shore of the Strait of Columbia River discharge, which is known to
Georgia, then through various passages, and flow northward during winter under the influence
eventually into Haro Strait (Fig. 19). However, of southerly winds. These reversals and intrusions
during strong northwesterly winds the flow was appeared to be directly related to storm winds
modified sufficiently so that the sediment plume along the coast, which raised the sea level at the
extended further southeast along the northern mouth of the Strait enough to reverse the flow
coasts of the San Juan Islands, flowed between within the western basin (Fig. 36). Significant cor-
Orcas and Lummi Islands, and then into Rosario relations were observed between along-channel
Strait (Fig. 21). Parts of these plumes remained in currents at the mouth and sea-surface height at
the southern Strait of Georgia at times, and they Neah Bay, and between coastal winds and the sea-
continued eastward and then northward along the surface height. The intrusions were observed
Washington coast in the vicinity of Cherry Point. south from Race Rocks as far as 90 km from the
Tidal currents were small in the relatively shallow mouth. The speed and duration of these current
water near Cherry Point, and variable wind- reversals implies that oceanic water on occasion
driven currents dominated. Flow patterns deter- could possibly reach as far east as Whidbey

Island. However, it is not certain whether the in- have yet been run. Finally, the model includes
trusions of coastal water actually enter the eastern wind and tidal currents, but time has not allowed
basin of the Strait; nor is it certain to what extent inclusion of the winter current reversals arising
storm-related conditions drive the circulation in from wind setup along the coast. These currents
the eastern basin. These questions are being are not yet sufficiently well understood to be
addressed during the present field investigations. modeled in the computer.
The oil-spill trajectory model, while still incom- Drift cards have been found on some beaches at
pletely developed, has nevertheless provided con- all times of the year. Their recovery in the western
,siderable useful information. A simulated oil spill, basin appeared related to local winds. Recovery in
assumed to be under the influence of easterly the eastern basin throughout the year appeared to
winds that were variable in space but constant in be independent of season; however, the flow
time, had trajectories starting from five release patterns distributing the cards around the eastern
sites in the eastern basin, all of which remained in basin remain unknown. The initial trajectory
open water for the duration of the calculations. model experiments described here also indicate
The simulation for westerly winds showed trajec- that beachings would occur, but more compari-
tories ending on beaches after a day or two when sons remain to be made with actual observations
the release sites were near the San Juan Islands, for details of the paths, particularly for those ex-
and after about five days when the sites were west ceeding a day or two in time.
of Port Angeles (Fig. 43). However, it is unlik'ely The details of the circulation for the southern
that the winds would remain constant for as long Strait of Georgia and for the western basin of the
as five days. A third case was run for time-varying Strait of Juan de Fuca are better known than those
but spatially uniform winds for a release site west for the eastern basin. Considerably more informa-
of Port Angeles and south of Race Rocks. Six re- tion should be available from the ongoing studies
leases were simulated at noon at three-day inter- in the latter region in about a year and the gaps in
vals, using computerized data from winds ob- knowledge partially filled. However, little is
served at Race Rocks for March 1976. After three known about processes occurring in the nearshore
days, two spills had been transported as far east as zone extending about a mile or so offshore any-
Admiralty Inlet, two were between New Dunge- where in the estuary, in the passages between the
ness and the release site, and two were slightly San Juan Islands, at the mouth of the Strait of. Juan
west of the release site (Fig. 46). Because of the as- de Fuca, and at the junction with Admiralty Inlet.
sumption of spatially uniform winds, the eastern- These areas must await future research.
most predicted trajectories should be regarded as So far, these studies have shown that in the
preliminary results only. Also, the east-west chan- Strait of Juan de Fuca a variety of transport pro-
neling of these mid-channel releases may be an cesses exist which could result in considerable re-
artifact, because the model does not include all the distribution of spilled oil (or any other contami-
details of the actual currents (data from the drifter nant). Although much work remains to better de-
experiment indicate that oil would likely reach the scribe and quantify the cause and effect relation-
@
a

v
t'

northern or southern shore). ships, much evidence has been presented that indi-
These test cases were trajectories from a typical cates iK-e-str
qng pg�sibility of signi icant volumes
March. However, March 1977 was not typical, of ntaminant,-,reachin-- eac es within- th@
g
and had oil been spilled then, its transport would estuary instead of being transported out -of the
have been to the west. Also, no summer cases estuary and

7. ACKNOWLEDGMENTS

Funding for a significant part of these studies
was provided by the U.S. Environmental Protec-
tion Agency to NOAA and managed by NOAA's
Puget Sound Project Office of the Marine Ecosys-
tems Analysis (MESA) Program. MESA provided
additional funding for this report. This support is
gratefully acknowledged. In addition, these funds
were supplemented by the Pacific Marine Environ-
mental Laboratory (PMEL). The National Ocean
Survey (NOS) was supported primarily by its own
funds with a small supplement from MESA. The
NOS also provided ship support for many of the
PMEL field activities, and assistance by the offi-
cers and crews was invaluable.
Special thanks are due Dr. Patrick B. Crean,
Dr. Richard E. Thomson, and Mr. W. Stan
Huggett of Environment Canada's Institute of
Ocean Sciences at Patricia Bay. Many discussions
of their work as well as assistance in the field have
greatly aided carrying out much of our own work.
Special credit is due many at PMEL who have
contributed to and made these studies successful.
Dr. John R. Apel provided many helpful sugges-
tions during the final writing.

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49
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LABOR AT OR I ES

The mission of the Environmental Research Laboratories (ERL) is to conduct an integrated program of fundamental
research, related technology development, and services to improve understanding and prediction of the geophysical
environment comprising the oceans and inland waters, the lower and upper atmosphere, the space environment, and the
Earth. The following participate in the ERL missions:

MESA Marine EcoS ystems Analysis Program. Plans, GLERL Great Lakes Environmental Research Labora-
directs. and coordinates the regional projects tory. Studies hydrology, waves, currents, lake
of NOAA and other federal agencies to levels, biological and chemical processes,
assess the effect of ocean dumping, municipal and lake-air interaction in the Great Lakes and
and industrial waste discharge, deep ocean their watersheds; forecasts lake ice conditions.
mining, andsimilar activities on marine GFDL Geophysical Fluid Dynamics Laboratory.
ecosystems. Studies the dynamics of geophysical fluid
OCSEA Outer Continental Shelf Environmental systems (the atmosphere, the hydrosphere,
Assessment Program Office. Plans and directs and the cryosphere) through theoretical
analysis and numerical simulation using power-
research studies supporting the assessment ful, high-speed digital Computers.
of the primary environmental impact of energy APCL Atmospheric Physics and Chemistry Labora-
development along the outer continental shelf
of Alaska: coordinates related research activities tory. Studies cloud and precipitation physics,
of federal, state, and private institutions. chemical and particulate composition of the
atmosphere, atmospheric electricity, and
W/M Weather Modification Program Office. Plans atmospheric heat transfer, with focus on
and coordinates ERL weather modification developing methods of beneficial weather
projects for precipitation enhancement and severe modification.
storms mitigation. NSSL National Severe Storms Laboratory. Studies
severe-storm circulation and dynamics, and
NHEML National Hurricane and Experimental develops techniques to detect and predict
Meteorology Laboratory. Develops techniques tornadoes, thunderstorms, and squall lines.
for more effective understanding and WPL Wave Propagation Laboratory. Studies the
forecasting of tropical weather. Research areas propagation of sound waves and electro-
include: hurricanes and tropical cumulus magnetic waves at millimeter, infrared, and
systems; experimental methods for their optical frequencies to develop new methods
beneficial modification. for remote measuring of the geophysical
RFC Research Facilities Center Provides aircraft environment.
and related instrumentation for environmental ARL Air Resources Laboratories. Studies the
research programs. Maintains liaiscn with diffusion, transport, and dissipation of atmos-
user and provides required operations or pheric pollutants'. develops methods of
measurement tools, logged data, and related predicting and controlling atmospheric pollu-
information for airborne or selected surface tion; monitors the global physical environment
research programs. to detect climatic change.
AOML Atlantic Oceanographic and Meteorological AL Aeronomy Laboratory. Studies the physical
Laboratories. Studies the physica@, chemical, and chemical processes of the stratosphere,
and geological characteristics and processes ionosphere. and exosphere of the Earth and
other planets, and their effect on high-altitude
of the ocean waters, the sea floor, and the meteorological phenomena.
atmosphere above the ocean. SEL Space Environment Laboratory. Studies
PMEL Pacific Marine Environmental Laboratory. solar-terrestrial physics (interplanptary, mag-
Monitors and predicts the physical and netospheric, and ionospheric); develops tech-
biological effects of man's activities on niques for forecasting solar disturbances;
Pacific Coast estuarine, coastal, deep-ocean, provides real-time monitoring and forecasting
and near-shore marine environments. of the space environment,

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