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+69 Coastal z information Center ftT 7 1970 UNIVERSITY OF PUERT-011CO btPA"0TMENT.'II0F ARINE SCIENCES M 'Y ATAGUEZ, P IINAL REPORT,QN OCEAN THERMAL ENERGY PROJECT touTAL 10 INFORMATIO ANTEIT TK 1073 .033 1976 AUGUST .1976 on@e All PROPERTY OF THE UNITED STATES GOVERNMENT NATIONAL OCE-ANG AND ATMOSPHERIC ADMINISTRATION 4- For Retention When no longer needed, please return to'. Technical Processes Branch - D823 FINAL REPORT Ocean Thermal Energy.Conversion: Resource Assessment and Environmental Impact for Proposed Puerto Rico Site NSF Grant No. AER 75-00145 August,-1976 by Donald K. Atwood*, Peter Duncan Marvel C. Stalcup**, and Michael J. Barcelona Present address, NOAA/AOML, 15 Rickenbacker Causeway, Miami, Florida, 33149 Present address, Woods Hole OceanograOhi6,1n@sUtution, Woods Hole, Mass., 02543 k CONTENTS INTRODUCTION 4 PART I: SURVEY OF HISTORICAL DATA 5 1.1 Bathymetry 6 1.2 Bottom Quality 6 1.3 Seismicity 6 1.4 Climate 6 1.5 Winds 1.6 Hurricanes 12 1.7 Tides 20 1.8 Sea and Swell 20 1.9 Water Masses 32 I.10 Temperatures 35 1.11 Salinity 35 1.12 Density 35 1.13 Currents 39 1.14 Nutrients 43 1.15 Oxygen 50 PART 11: 0CEANOGRAPHIC SURVEY OF POINT TUNA/YABUCOA SITE 52 Ii.1 Extent of Survey 52. 11.2 Bathymetry 57 11.3 Temperature 57 11.3.1 Seasonal Variations 57 11.3.2 Comparison to Hawaii Area Temperatures 11.3.3 Diurnal Variations 69 11.4 Salinity 69 11.5 Nutrients 77 11.5.1 PhospLiate 77 11.5.2 Nittate/Nitrite 77 11.5.3 Silicate 83 11.6 Oxygen 83 11.7 Geostrophic Currents 83 PART III: CONSIDERATION OF OTHER SITES NEAR PUERTO RICO 97 PART IV: COHMENTS ON TRW SYSTEMS' LIST OF DESIRABLE CRITERIA 99 FOR AN OTEC TEST SITE -4 PART V: CONCLUSIONS 101 PART VI: SEMINARS 102 PART VII: BIBLIOGRAPHY 103 2 ACKNOWLEDGEMENT Computer plots included in this report were compiled using plot programs from C.P. Duncan and J.R. Duncan, 1974, Plotter Programs For Oceanographic Data, National Research Institute for Oceanology (Durban, South Africa) IG74(5):1-52. Other figures were drawn by Mrs. Vangie Fradera Hernandez from the authors' pencil sketches except where other- wise noted. Bathymetry figures in Section 11.2 were drawn at Woods Hole Oceanographic Institution. 3 FINAL REPORT. Ocean Thermal Energy-Conversion: Resdurce Assessment and Environmental Impact for Proposed Puerto Rico Site NSF Grant No. AER 75-00145 August,-1976 by Donald K. Atwood*, Peter Duncan Marvel C. Stalcup**, and Michael J. Barcelona Present address, NOAA/AOML, 15 Rickenbacker Causeway, Miami, Florida, 33149 Present address, Woods Hole Oceanographi6-InstItut'lon, Woods I Ne,- t ,;- Hole, Mass., 02543 CONTENTS INTRODUCTION 4 PART I: SURVEY OF HISTORICAL DATA 5 I.1 Bathymetry 6 1.2 Bottom Quality 6 1.3 Seismicity 6 1.4 Climate 6 1.5 Winds 1.6 Hurricanes 12 1.7 Tides 20 1.8 Sea and Swell 20 1.9 Water Masses 32 I.10 Temperatures 35 I.11 Salinity 35 1.12 Density 35 1.13 Currents 39 1.14 Nutrients 43 1.15 Oxygen 50 PART II: OCEANOGRAPHIC SURVEY OF POINT TUNA/YABUCOA SITE 52 II.1 Extent of Survey 52 11.2 Bathymetry 57 IT.3 Temperature 57 11.3.1 Seasonal Variations 57 11.3.2 Comparison to Hawaii Area Temperatures 66 11.3.3 Diurnal Variations 69 11.4 Salinity 69 11.5 Nutrients 77 11.5.1 PhospiLate 77 11.5.2 Nit-tate/Nitrite 77 11.5.3 Silicate 83 11.6 Oxygen 83 11.7 Geostrophic Currents 83 PART III: CONSIDERATION OF OTHER SITES NEAR PUERTO RICO 97 PART IV: COMMENTS ON TRW SYSTEMS' LIST OF DESIRABLE CRITERIA 99 FOR AN OTEC TEST SITE PART V: CONCLUSIONS 101 PART VI: SEMINARS 102 PART VII: BIBLIOGRAPHY 103 2 Jw ACKNOWLEDGEMENT Computer plots included in this report were compiled using plot programs from C.P. Duncan and J.R. Duncan, 1974, Plotter Programs For Oceanographic Data, National Research Institute for Oceanology (Durban, South Africa) IG74(5):1-52. Other figures were drawn by Mrs. Vangie Fradera Hernandez from the authors' pencil sketches except where other- wise noted. Bathymetry figures in Section 11.2 were drawn at Woods Hole Oceanographic Institution. 3 INTRODUCTION As a combined result of declining fossil fuel.reserves and man's increasing technological capability in the oceans, the concept of ex- tracting vast reserves of thermal energy stored in the tropical sea sur- face by a process called Ocean Thermal Energy Conversion (OTEC) is rap- idly approaching a functional reality. As part of a program to exploit this energy reserve the Research Applied to National Needs (RANN) Pro- gram of the U.S. National Science Foundation (NSF) has funded a one year. study of a specific high potential OTEC site near Puerto Rico. This publication comprises the final report of that study. The,site chosen is near the southeast coast of Puerto Rico just off Point Tuna and close to the town of Yabucoa (See Location Map, Fig- ure 1). It was considered both as a high potential site for an OTEC prototype plant and as a typical "near island" site. The potential of southern coasts of the Greater Antilles for OTEC sites is great and.has been discussed in detail elsewhere (Duncan, Atwood, and Stalcup, 1976). The work reported on consisted of two parts. Part I - A survey of existing oceanographic and meteoro- logical data at and near the site and for other pos- sible sites near Puerto Rico Part II - A survey of the specific site to confirm the oceanographic conditions prevalent there. The first part of the report is derived from a literature survey in which the aim has been to set down the oceanographic and meteorological facts concisely. A complete list of the works consulted is listed in the bib- liography, but, references in each section have been kept to a minimum to save the reader a plethora of parenthesis. Our conclusion is that the specific Yabucoa site is oceanographi- cally excellent for ocean thermal energy conversion and that it is probably typical of several sites along the south coasts of the Greater Antilles. A AA 4 A T L A N T I C. 0 C E A S Tho Culebra P-U.: Mona RA-C Vieques Passage ij < .......... St a., Mona @Serial evINV Sta. 0 c A R I B B E A N S 0 10 20 L L---j statute miles 670 660 61 FIG.1 LIOCATION MAP FOR SURVEY AREA PART'I: SURVEY OF HISTORICAL DATA 1.1 Bathymetry The site surveyed is located to the south-east of the island of Puerto Rico, on the Caribbean side of the Puerto Rico - Virgin Island shelf (see Figure 2). The narrow continental shelf and steep conti-- nental slope at the site ensure that depths in excess of 1000 meters are found within 5 km of the shore, between the'island,of Puerto Rico and a sill which extends eastwards and separates the Virgin Islands Basin from the Venezuela Basin, in which bottom temperatures are slightly colder than in the Venezuela Basin. Results of more detailed surveys of the Isite.are discussed in Part II of this report (section 11.2). 1.2 Bottom Quality A core taken at 17*46' n, 66*01' W at 1270 meters depth on the island slope of Puerto Rico, some 18 km to the southwest of the site, revealed that the first meter of sediment is a mixture of clay, silt, sand and gravel. In general, the region is one in which the bottom shal- lower than 200 meters is dominantly gravel and rock, and deeper than this is mud. Data taken from SP1&911. 1.3 Seismicity The following qualitative data is contained in U.S.N.O.O. Pub. No. 700 (V). The entire island of Puerto Rico falls within the seismic area extending from'Panama, through the Andes and coastal Venezuela, along the Windward Islands to Cuba. In addition, two submarine faults strad- dle the island to the north.and south. Consequently it falls within a region where earthquakes are reported to be "relatively frequent", with epicenters at depths between 70 and 300 km. Tsunamis have been reported from all Puerto Rican coastal regions facing the Caribbean. No volcanoes are known in Puerto Rico. 1.4 Climate The site has a marine tropical climate characterized by a high mean annaul air temperature which varies little with season (80.3* F, + 3*), and a high mean relative humidity (78% ). Figure 3, drawn from data in "Summary of Synoptic Meteorological Observaiions, Volume 4" (SSMO Vol. 4), illustrates the mean seasonal temperature cycle with an envelope of the observed maxima and minima. Figure 4, from the same source, shows the frequency distribution of relative humidity. SSMO, Vol. 4, is a valuable reference for climatic conditions and should be consulted by those interested in the diurnal variations of wind, cloudiness, fog, relative humidity, etc. Abbreviated tables for oceanic conditions from "Sailing Directions" (H.O. 21) are included here as Figure 5 and Table I-. 6 10-30 CABO ... SAN JUA% BATHYMETRIC MAP OF THE SUBMARINE SLOPE AREAS V3 ADJACENT TO PUERTO RICO 0 1 2 3 4 5 Scale: noutical mi es Contour Interval 100 meters 4.4.4,ro.LJAYA.@ A:: ri8*00 N, A 6.6100' 65*30, FIG.2 GENERAL BATHYMETRY AP 7 95- A IIR TEMPERATURE OF OCEANIC REGION SOUTH OF PUERTO RICO FIG. 3 MAXIMUM 90- DRAWN FROM SSMO Vol. 4 u- 0.1 w ir 85- D MONTHLY MEAN cr w ANNUAL a. m I MEAN= w 80@ 80.39 75- MINIMUM 70 i F M M A S 0 N A , @w 1* o &@ 50- 40- z w 30- a w ir U. 20- z 00 w X w 10- 0- 0 30 40 50 60 70 80 90 100 RELATIVE HUMIDITY FIG. 4 DISTRIBUTION OF RELATIVE HUMIDITY-OCEANIC REGION SOUTH OF PUERTO RICO ..... D wn. f rom S.S M O,vo 1. 4 85* 80. 751 70* 65* 60* 301L 30' 25t 25* 20'@- -20* El. 15*- MG -1.5* IV-1\1 85* go. 75' 76- 60* F I G. 5 LOCATION OF OCEAN AREAS F AND G (From H. 0. 21 10 UNIT AREA F Months Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. at 16 Pressure .......................... of obs. %! 1017 1017 1016 1016 1016 016 1017 1016 1016 10166 1016 Sea le pressure ................. : ............... MIledian 1018 101 10 1017 11017 1018 1017 1016 1016 1017 1017 (Millial.) -------- I . is II I -------------------------------------- 34 of obs 1019 109 to leis 1018 1019 10 80 71017 1017 1018 Temperature. air (I F.) -------------------- ----- of obs. @2 176 76 76 77 is A0 80 91 at 77 Cdlan 77 80 81 81 92 82 81 91 78 X of ohs. S 78 82 82 82 8.3 83 92 92 -19 I I IIII Iso I sol Temperature, mean sea surface (0 F.) ...................... 781781 791 811821821831 8;1831 821 80 observations with precipitation ---------------_-_---- 1314131 41 71513151 61.7 1 5 1 3 Cloudinem: Percent of observations with 5i cover ... ------------ I ------ W48 32 48 38 37 39 53 44 48 42 48 ----------- 76 11 81 72 65 62 63 77 68 70 70 76 cover ........... :.............. go 91 95V 94 so 81 go 89 88 88 91 Visilbility: Percent or observations.. . ................... < 2 miles- .......... 1 01 1 0 < S miles ............ 0 2 0 21 1 1 1221 10121 Median-Half the obseevatlons fall below and halt above this point. !Z Equal to or less than. 5 Equal to or more than. < L*.m than. OCEAN AREA G Months Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Pressure. ....... ..... of bs. Z 1011 1012 1012 101110 1, 1012 1012 1011 1010 "1 00 1011 II I 11012 toll Sea level 5;@WL@W --------------------- ... hedlon 1012 1013 10 30 21OL2 10 210 31 101? 'loll L 1012 (Millibars) --------------------------------------- of ohs. 5 1014 1015 IOL5 1013 1013 1014 1014 1013 1012 1012 1012 1013 Temperature, air (0 F.) ------- --_-_--------- 77 76 77 78 79 2 101 78 Vied' IOZ 78 77 78 In 91 81 at, '82' 6.21 $82 81 so Yj of obs. 1; 80 79 79 so 92 82 82 93m 83 62 at I- I- Iso -1011 Temperature, mean sea surface (* F.) ....... ........ --------------- SO 79 79 80 81 92 92 83 84 83 V at Pre@lpllallon, t of observations with precipitation ------------------------ 1134 4 488811 9 a 7 Cloudiness: Percent of observations witb Z 16 cover ............................ 45 50 52 42 41 31 34 41 40 41 39 48 Z % cover --------------- 72 78 78 71 68 62 63 70 69 72 70 72 Z % co;W ------------_ 90WW W a 83 84 89W W 90 98 Visibility- pareant of observations ....................... < 2 miles ........ III I < 3 miles ........ . 222 3 2222 2 1 2 101 o Median-Halt the observations fall below and hall above this point. Equal to or less than. Equal . or more than. <len ban. I: From: H. 0. 21. 1.5 Winds The following is of doubtful value to the design of an OTEC plant which must be designed to withstand hurricane-force winds and their effects (see Hurricanes), but it is included for completeness and for its use in considering the requirements of surface-supply,vessels. The propo sed Yabucoa site-falls within the climatological region of the easterly Trades, which in the Caribbean are"relatively constant in speed and direction throughout the year (see Figure 6). the center of the Bermuda high moves slightly north in-the summer, and south in winter so that the dominant wind direction at the site is easterly in @spring and summer and NNE in autumn and winter. Windspeeds average from 9 to 10 knots in autumn to 12 to 15 knots in summer (H.O. 21) but the passage of fronts and easterly waves interrupts the normal Trade- wind pattern and strong northerly winds of greater than 28 knots may occur from November to April, with a frequency of about 2 % (SPI89II). A diurnal variation is common in the Trades, with winds dropping at nightfall and increasing to a maximum in the afternoon. At Yabucoa this diurnal variation is accentuated by the landbreeze caused by the presence of the Puerto Rican landmass, with slight northerly winds being common during the night. A crude graphic summary of oceanic wind conditions around the is- land of Puerto Rico is shown in Figures 7 - 10, drawn from data in SP- 18911. More detailed data is available in SSMO Vol. 4. 1.6 Hurricanes The majority of tropical cyclones in the Caribbean occur between the months of June and November inclusive. About 58% of these reach hurricane force (H.O. Pub. 21). In the five-degree square bounded by 15' - 20*N and 65* - 70*W, which includes the island of Puerto Rico, some 130 hurricanes may be expected within a one hundred year period (Figure 11). Typical hurricane tracks are shown in Figure 12. The expectancy of hurricaneswithin the site surveyed is naturally much less (about 13 in a hundred years), but sufficiently probable to warrant consideration since: M Windspeeds may be in excess of 130 knots, with sustained speeds between 65 and 90.knots. (ii) Waves as a result of these winds are characterized as 11mountainous". (iii) The surface of the sea is raised by up to one meter in the eye of the storm because of the locally lowered atmospher- ic pressure. This "dome" moves with the eye, producing the effect-of a single wave between 25 and 500 n.m. long, tra- velling at about 12 knots. Uv) Drastically lowered sea surface temperature caused by hur- ricanes, with noticeable effects to 500 meters. The iso- therms rise sharply under the eye, as a result of the 12 jANUARY FEBRUARY G) MARCH z APR IL rrl w MAY -n 0 IZ F NZ z JUNE rn t CA U) JULY G) M cm .1 M U) AUGUST n SEPTEMBER M 0 OCTOBER 0 NOVEMBER DECEMBER 30 -15 WINDS -FEBRUARY 25- (n 20- -10 0 z W cn z I%%. cn 15- cr W W W ALL 0- NW S N,SE NE E W z 10- 5 3: 5 0 5 10 50 100 FIG-7 PERCENT AS GREAT OR GREATER THAN (10 % of al I winds have speeds greater than 13 m /s) 30 -15 25,- WINDS MAY cn 20- -10 .0 z W cn z cn 15- ir t-n a W W W N E NE E ALL a- W z 10- -5 5- S4\ \NE 0 0 1 5 10 50 100 FIG.8 PERCENT AS GREAT OR GREATER THAN. (10% of all winds have speeds greater than 12.5 m/s) 30 -15 25- WINDS -AUGUST cn 20- -10 0 z W cn z *,%. 15- cn 0 cr W W W N SE NE E ALL 0, W cn z 10- 5 5 "' \ \N,' \N E 0- 1 1110 1 5 10 50 100 FIG-9 PERCENT AS GREAT OR GREATER THAN (10% of all winds have speeds greater than 12.3 m/s) 30 -15 WINDS -NOVEMBER 25- 20- -10 0 E NE ALL z uj Y_ (n z (n cr 15- S SE uj U) 0 -5 z 10- 5 0 5 10 50 100 FIG. 10 PERCENT AS GREAT OR GREATER THAN (10% of all winds have speeds greater than 12.5 m/s) FIG. 11 OCCURRENCE OF TROPICAL CYCLONES IN THE FIVE DEGREE SQUARE BOUNDED BY 1500-200N, 650-70OW 50- - -30 00 0 tc) 40- w z w OD a z CD -20 30- w cr_ w w CL a w 20- w 0- x -10 w D cr_ w 0 m cr. lo- w D co z D z 10 JUNE. J ULY AUGUST SEPTEMBER OCTOBER NOVEMBER MIMI MI'm M M M mm M 120* 115* 110, 105, W* 95. go- gs* go* 75, 70, 65* 60- 55' SV 45' 40' 35' 30' 2S' 20' is, 10, D. 5*E so. 10. FIG-12 TRACKS OF SOME DEVASTATING NORTH ATLANTIC HURRICANES. 35* From: H.O. 21 5 10 40' 35' 25* 30' NO. DATE 20* 1Aug 2Au,.@ 18 5, M3 3Aug. 27 Sept. 3, 1900 25, 4Sept. 10-30, 1906 5Aug. 5.22, 1915 6Sept. 6.22, 1926 7Sept. 6.20, 1928 8Aug. 31-Sept. 8. 1935 is, 9Sept. 17-22, 193EI 0Sept. 9 1r., 1944 20. IAug. 25'31, 1954 12 Oct. 6-15, 1954 13 Sept. 22-29, 1955 Opemcirctes indicate a.m. PositiOns 75 meridian time EXCEPT Track 1 10 10, F0 12 13 a gs. so t 70' 65, 60' 55. so. 45* 40. 35 30 25* pressure imbalance and the oceanic divergence caused by the Ekman effect as the winds blow water away from the center. (See Figure 13). 1.7 Tides The tidal cycle on the Caribbean coast of Puerto Rico is of the mixed diurnal type. The site is near the amphidromic (nodal) point of the principal lunar semi-diurnal (M2) tidal constituent, which reduces the semi-diurnal contribution to tidal height. Figure 14 has been drawn from the 1974 Tide Tables produced by NOAA, for the coincidence of:new moon and summer solstice to illustrate the maximum typical tidal range, which is about 55 cm. At the coast, therefore, the cause of major fluc- tuations is likely to be meteorologic al with run-up during storms. In deep water, both tidal and meteorological effects are minimized. 1.8 See and,Swell As the winds in. the Caribbean near Puerto Rico shift from easterly in spring and summer to NNE in autumn and winter, so the oceanic wind- waves vary in direction (see Figures 15 - 18). Swell, however, has a dominantly easterly component all *the year round. (See Figures 19 - 22). These figures were drawn from the data contained in SP189II for the oceanic region surrounding Puerto Rico and do not take into account the masking at Yabucoa by the islands of Puerto Rico and Vieques. The information is included for its value as a guide to the conditions which may be expected while the plant is being towed to the site from its place of construction. A noticeable amelioration of conditions is found along the southern coasts of the Greater Antilles. Table II has been taken from H.O. 21, and refers to the south exposure of the islands of Jamaica, Cuba, His- paniola and Puerto Rico. The percentage of "calTn" swell is over 85% for winter and summer in coastal waters and less than 19% in the open ocean. Similarly, swell in the coastal area is never observed in the quadrant N to E (0' to 90*) but in the open ocean this quadrant accounts for over two-thirds of all observed swell, and nearly all observations greater than 12 feet high (3.6 meters). Very detailed monthly averages for the south of Puerto Rico are contained in "Summary of Synoptic Meteorological Observations", Volume 4, published by the U.S. Naval Weather Service Command in 1974. The region covered by this Summary overlaps Puerto Rico to the east and west, protruding into the Mona Passage and to the Virgin Islands. The aver- ages, therefore, more closely resemble those for the oceanic regions of SP18911 than those in the table above. Note should be taken of the relatively frequent passage of hurricanes 20 SCHEMATIC REPRESENTATION OF DOMING CAUSED BY A HURRICANE HIGH PRESSURE LOW PRESSURE HIGH PRESSURE WIND WIND DOMING CAUSED BY I meter TMOSPHERIC PRESSURE 0- DIFFERENCE MSL EKMAN FLOW EKMAN FLOW w ISOTHERMS -i cn cn cr -i w w w z > w a- w w x w 1000. FIG. 13 PREDICTED TIDE FOR PUERTO MAUNABO, 15-24 JUNE, 1974 (GMT) DRAWN FROM NOAA NEW SUMMER TIDE TABLES OON STE -40 -30 -20 -10 0 15 j6 17 is 19 20 21 22 23 24 FIG. 14 JUNE 1974 Fl G. 15 10 3 w SEA -FEBRUARY w U- -2 z cn cr_ NE ALL w 5- w M w SE N 0 0 1 5 10 50 100 E SE N PERCENT AS GREAT OR GREATER THAN (10% of all seas are greater than 2.2 meters) FIG.16 10 3 w SEA - MAY w U- -2 z cl) 5- w SE NE E LL w w -.1 04 0 1 5 10 50 100 PERCENT AS GREAT OR GREATER THAN (10% of all seas ore greater than 2.0. meter*s) FIG.17 10 -3 SEA - AUGUST W W W -2 z cn cr W un 5- SE NE E ALL W W cn 0 0 1 5 10 50 100 PERCENT AS GREAT OR GREATER THAN (10% of all wove heights are greater thon 2.3 meters) FIG. 18 10 SEA - NOVEMBER W W U- -2 z cn cr- W 5- ALL NE W Ej, x E < SE N W co 01 0 5 10 50 100 PERCENT AS GREAT OR GREATER THAN (10% of all wave heights ore greater than 2.1 meters) FIG. 19 12 SWELL FEBRUARY 10- 3 W W u- N SE NE E ALL cn z -2 cr- W W W 5- r -i W 0 so 1 5 10 50 100 PERCENT AS GREAT OR GREATER THAN (10% of all swell is greater than 3.4 metee.t) FIG. 20 12 SWELL- MAY. 10- W W SE \N E ALL U- cn 2 Ix ui 00. 5- W 01 0 1 5 10 50 100 PERCENT AS GREA1 OR GREATER THAN. (10%-of all swell is greater than 3.4 meters) tM FIG. 21 SWELL- AUGUST 10- -3 W W U- z SE NE E ALL cn cr W CD ui W W cn 01 0 0 5 @ \NE 50 100 PERCENT AS GREAT OR GREATER THAN (10% of all swell is greater than 3.2 meters) F I G. 22 SWELL - NOVEMBER 10 -3 W W z W SE N NE E ALL 4 W W- 5 W call 0 0 5 10 50 100 PERCENT AS roREAT OR GREATER THAN (10% of all swell is greater than 3.3 meters) 80. 70. 60'. WINTER.. -SUMMER THISS U REIS DESIGN ED TO GIVE THE PERCENT FIREQUENCY OF SEA AND EA* SWFLLEBY LIRECTION AND HEIGHT FOR VARIOUS COAS'r.L ALINEMENT$. <3' @12' IOTAI 13, IV-51151111i'Ll' t2llTOTALI THE DATA Afll@ APPLICABI.E TC NFARSHORE WATERS WITHIN TEN MILES OF THE COAST. EXCEPT FOR 6EPMUDA WHERE THE LATA APPLY TO THE AP- si51 N, 6N.1 J@* I PROACHES TO ST. GEORGES HARBOR THPOUGA FIVZ FATHOM HOLE. THE is1 17 NE711 1 10 ALINEME TS MA,E BEEN SELECTED ON THE BASIS OF SIMILArITY OF ELI E2971 2 1 39 POSIJRE,NMETEOROLCGtCAL C0140:11ONS, AND OBSERVED SEA 0 SWE _1_ 385 1 44 _L_ DATA. WAVE CONDITIONS AT SPECIFIC COASTAL LOCATIONS MAY VARY FROM _LE 1211 13 SE 231 25 THE PRESENTED DATk BECAUSE OF NONCONFORMITY TO THE GENERAI. 84 @. 4S2 2 CHARACTERISTICS OF THE ALINEMENT. THE GENERAL NATURE OF IIHIS -iw- - -2 SWI I STUDY DOES NOT PERMIT AN ANALYSIS OF SEA AND SWELL CONDITIONS L-2 FOR EACH SPECIFIC COASTAL LOCALITY. * MEANS LESS THAN 0.5 w2 21 1 NWJ5 5NI I I ITOIALl 831811 93 TOTAL 65 CALM7 NO. 003.2,203 CAL14 19 NO. 093. 1943 WINTER SEA SUMMER SWELL 40* 11-61 V-121 -IZ' TOTAL 11-61 61-1211 L21 TOTAL <3, 3-5,1 .1z' TOIAIJ 43, 31-51 S-4- 41@121 @121 TOTAL N4 2 6IN1 2 2L 12 1 12 1 N411 NIE Is _ _.L NE 10 7 is NE9 4 13 16 NE 241 14 E16 12 29E26 is 44 E26 26E271 __2_7 7jE2 1 3SE7 4 11 _T7_ SE9 7_0 _s SE 16 1 S Ss 1 -75 6 SW S Sw3 3S2 2 W w w 3wI I @vw_ NW NW 1 -L Nw1 1 32 22 TOTAL 43 26 to-, 4 4. 11 9@ LOTAI 63 65 CALM .44 NO. OBS.1636 CALM 30 so. Ols. 1998 cama CONFUSED NO. OSS-8301 CALM 35 "(1.0113.5982 SWELL WINTER SUMMER I'_" 161-12; > 12, T 0 1 AL 1 11-61 16--k2' >%I, TOTAL SEA N I I.@3' @Izl TALI 1 @31 IV-51151-1111fIll-121 >12,lrOTALI NE Na aN1 4* 1 14 E E E342 36 HE 302It * 33 SE A SE 4 2- 6 E38 39E404 3 * 41 S 1 5 1 1 7 SE41 SE 6 S 2 w I Sw 3 1 4 sI* S 2 W w 2 2 SWI* SINI Nw I *1 2NW I I I wI wI TOTAL I1_4 L I I IITOTAL 1-5 5 1 1 201 NWI2* NW 30-L CALM 89 010. OBS,6202 CALM 80 NO-093 6637 OTA 894 1 TOTAI A is- 30' CALM6 NO. Olls. 1985 CALM5 $10. OBS. 2119 SWELL 11-91 41-L21 >IV TOTAL 1-81 1 61-1211 >121 TOTAL NE NE E E SES SEa 5 13 S Sw -1 lw wI W H NW Nw T".-T". -, IOTA,9 4b CALM 89 CONFUSED N0.09LIZ65 CAL14 85 No, OBS. 1388 ;o Lo o' 0 2r- 20' JkM@AICA. CMA. IS Ali IOLA, PUERT@"RICO (SOUTHl;;;0Sl AVERAGE SEA AND SWELL CONDITIONS FOR COASTAL WATERS (PERCENT) 76- N' w w 2 S w E43 @N N E i'E E E ,E SE S S SW W VY W @N Tft TABLE II:.From: H. 0. 21 31 through the region (see Hurricanes, section 1.6). Resultant seas are not listed in these averages and reliable estimates of wave height are still being sought. The plant should be designed to withstand hurricanes on the site. Depending on the place where the plant is built, the safest approach for the tow to the site is along the southern coasts of the Greater- Antilles. 1.9 Water Masses A floating OTEC plant 1000 meters long will-pass through four dif- ferent water masses which have vastly.different origins and properties which need to be considered. From the surface to about 100 meters the Tropical Surface Water is found with high temperatures (25* - 29*C) and salinities between 33 */oo and 36 O/oo but usually less than 35.5 '!oo. This water mass has its origin in the tropical rain belt under the equa- torial atmospheric trough. The salinity is also somewhat decreased by river run-off from the Amazon and Orinoco Rivers before the North Equa- torial Current passes the Lesser Antilles to become the Caribbean Cur- rent. The warm water wedge of Tropical Surface Water (TSW) attains its greatest thickness (about 100 meters) along the coasts of the Greater Antilles because of the geostrophic tilt of the isotherms as the Carib- bean Current moves westwards. Figure 23, a temperature section along 67*W from Puerto Rico to Venezuela, illustrates this wedging effect. The 20*C isotherm is 210 meters below the surface at Puerto Rico, but only 120 meters at Venezuela. Beneath the TSW, between 100 to 200 me- ters, is found the Subtropical Underwater, which has its origin beneath the Bermuda atmospheric high. This water mass is more constant in char- acter, varying only about 20' - 24*C and 36.8 0/-- - 37.2 O/o-. A large density difference is found between these upper two water masses, maintaining them essentially separate and retarding mixing despite their contiguity. (See Density, section 1.12). At depths of 600 - 800 meters the Antarctic Intermediate Water is found, which is characteristically 60 - 70 C, 34.8 O/o.. At 1000 meters the influence of the North Atlan- tic Deep Water (NADW) which flows into the basin over the Anegada/Jung- fern Sill is seen with temperatures of 4* - 50C, and salinities very near 35 */oo. This last-water mass extends to the bottom.in the Vene- zuela Basin, and is over 3000 meters thick in parts. Since it is some- what different than NADW, e.g., in silicate content,.it is more aptly called Venezuela Bottom Water (VBW). A.rQugh estimate of the amount of this deep water in the Venezuela Basin alone is in excess of 150,000 cubic kilometers. These water masses are most easily identified by their characteristic temperatures and salinities on a Temperature - Salinity (T - S '/oo) plot (Figure 24) which oceanographers find con- venient for water mass analysis. However, this type of plot does not show the relative proportions, nor the absolute amounts of water present and should be interpreted accordingly. 32 F I G. 23 D IS TAN CE, km ------ cm N 0 100 200 300 400 500 600 700 800 900 S w 28 26 24 22 100 20 18 200- 16 12- 300- 400- 10 8 500- 600- 700 - ro 800- X 900 - N 5 X 1000 N 1100- N X N N N X 1200 1300- (5-0 R/V CRAWFORD CRUISE 72-27, TEMPERATURE PROFILE 1400L LA PARGUERA, P.R. LA GUARA,VENEZUELA 11, 1 tv ,v 4 mmmmmmmmm mmmmmm m mini TEMPr-RATLIRE a C 26 27'2e 9 0 FIG. 24 0 -20-21 22232425 6 7 e' '9 1 0 11 12 13 14 '1 C 6 7 le 1:9 TS-PLOT FCR STAI .33 2739 2747 '592e _n. 4 -694 '600 0601 2610 33.8 2611 16 70 26 1 34 2632 2649 165, 34.2 1 2661 Z662 16 0 70 0677 27k-e 27CI. A 3-4.6 .1712 0713 w -714 -P- IF- 430 33 35- 34 271S V BY 16 w 71 1-9 1725 > 7 7 2726 .2727 5.4 z '7128 37;. 8 36 T.- I.. NI 36.2 iv 36.6 6 40: 37 I.10 Temperatures The strong westward-flowing Caribbean Current causes a geostrophic tilt of the isotherms, so that a wedge of warm water is always found in the northern part of the Caribbean Sea (Figure 23). Large tempera- ture differences with depth are therefore found along the south coast of Puerto Rico. Figure 25 shows the-variation of in situ temperature with depth at the PESCA serial station at 17'38' N, 67* W. The wedge. of warm surface water, the sharpness of the thermocline and the rela- tively invariant temperatures at depths greater than 750 meters stand out well. Surface temperatures vary about 3.5 ', but at 1000 metet s the variation is less than V C. By using the mean surface temperature as a reference, an estimate of the mean temperature difference between the surface and any depth can be derived from the lower abcissa of the figure. In this and the next diagram the slight adiabatic cooling (about 0.01*/ per 100 meters) which occurs when water at depthis brought to the surface has been ignored. Figure 26 has been drawn from the same data to illustrate the vari- ation with time of temperature at a single position. The 25* C isotherm lies at about 100 meters, with small deviations. This ensures a thick warm surface layer which is accentuated in the summer months by an increase in temperature of the water above 100 meters to as much as 29*C. This warming is not the result of local insolation alone, butis gener- al for the Caribbean. The variations in depth of the 15'C isotherm may be due to reversals in the current. The temperature difference between the surface and 1000 meters has been extracted, and is presented as a time-dependent variable, showing that this difference is never less than 20.31 C, and can exceed 230 C. I.11 Salinity Figure 27 shows the variability of salinity with depth at the PESCA serial station. Surface waters show a wide variation (34.2 '/-o to 36.2 '/.o) due to seasonal effects associated with precipitation and discharge from large South American river systems (Amazon and Orinoco) (Froelich and Atwood, 1976). At about 150 meters a high salinity (36.5 */,,. to 37.2 */..) core called the Subtropical Underwater is found. Between 600 and 800 meters a water core called the Subantarctic Inter- mediate Water occurs with a minimum in the salinity (about 34.8 0/00) and below this is found the almost constant Venezuela Basin Water sa- linity of about 35.00 O/oo. Note that although there is extensive vari- ation in surface salinity there is very little scatter at 1000 meters. For a more complete discussion of the above mentioned water cores see section 1.9, Water Masses. 1.12. Density This section is included fortwo reasons: 35 2. 3. 4. G. 6. 7. '-J, 9. 10., 1 1,12. 13. 1 -1. E-3. 16.. 17. 18. 19. 20. 21, 22. 23. 2-1. 2S. 26. 27, 28,29.30, YE@P@R@TURlt-C FIG. 25 TEMPERATURE vs. DEPTH SCATTER PLOT ALL DATA, 1971-1973 XX XN 17 40'N , 67 0 00'W '21ov, C "A@ v w e.g. MEANAT 500wI5*C CL w Z32e. 0 20 15 10 5 0 MEAN AT, SURFACE TO ANY DEPTH FIG. 26 VARIATION IN TEMPERATURE WITH TIME AT PESCA SERIAL STATIGN---- 1973 1971 1972 J F M A M J J A S 0 N 0 J F M A M J J A S 0 N D i --F M A M J J A S 0 N -23 23- 0 0 -22 7 0 20 20 R/V CRAWFORD STATION NUMBERS F C, m CD 0 U) 0 a- 0 oo mo ID ID 10 w to 'D r.. 0 g C-i CIA N N N ci N N cli -0 0 25 100 00 20 200 -zoo- -300 (n 15 w -Ili @@ 400 Ld LLI 400 - ui w -500 500- 10 (L CL -600 ui Ld 0 600- -700 Too- -800 600- -900 wo 1000 1 f I I I I F M I A I M J J A S 0 N D J F I M A I m A s 0 N 1000 i F M A M i J A S,.. 0 N D I J 1972 1973 lid 35.0 36.0 37.0 3e. e %x X@ Xq: X* xx x44 @A gxA SALINITY X xx "A xx,41 x @i x N zi, 1. 16-@ FIG. 27 SALINITYIDEPTH AT PESCA SERIAL STATION @;ee. oL co A 600. :4. i) To aid in the design of a floating plant ii) To consider the consequences of the proposed heat- exchange on the water column. The density of sea water depends on the. temperature, salinity and pressure in situ. In the surface waters the pressure effect is negli- gible, bx@t_a@t_1000 meters accounts for a 0.4% increase in the in situ density. Figure 28 illustrates the variation of density with @_ep7t_h_at the PESCA serial station,, and an estimate of the variability of density in the surface waters with season. The total density change between the surface and 1000 meters is about .01 g/cc, but this small difference is quite sufficient to keep the water masses separate and distinct. As water is pumped up from depth (say 1000 meters) it is relieved of the pressure and expands slightly. Even though there is a slight adiabatic cooling effect, this expansion effectively reduces the density. Allowing for a 2* C increase in temperature as this water passes through the condensor, the density of the water at the outflow will be about 1.02735 for an ini- tial temperature and salinity of 5.2* C and 34.9 */oo. Assuming that the surface water is 27.00 C, 35.4 0/,,,,, with a density of 1.02304, the out- flow water willsink, be compressed, and come to rest at a depth of about 800 meters. Similarly, the surface water which is cooled by 20 C in the evaporator will have a resultant density of 1.02366 which will float above the thermo- cline - thereby reducing the effectiveness of the heat source. However, if both intakes are exhausted through the same pipe, being mixed in the process, the density of the resulting mixture will be 1.02587 and the mix- ture will sink to 200 meters, well removed from either intake and below the euphotic zone. Any further mixing which takes.place after the outflow water has reached an equilibrium depth will result in a denser water mass which will sink further by the process known as caballing. The hydrostatic pressure at 1000 meters is about 100 atmospheres and as water is pumped up from this depth it will be replaced laterally from the immense reservoir of VBW. At the surface warm water intake the pressure head is much less, but if the intake is at 20 meters, the replacement supply is more likely to travel horizontally (driven at 30 psi) than vertically. Since the out- flow will sink to intermediate depths, it is quite possible that the plant could operate indefinitely even in the absence of currents. 1.13 Currents A number of atlases of surface currents in the Caribbean have been prepared from ship's drift observations, and they all show the same gen- eral pattern, a westerly and northwesterly flow at up to 2 knots, with some flow through the island passages connecting the Caribbean and North Atlantic Gyre. Figures 29 and 30 are reproduced from Wust (1964) but should be considered as giving only a general picture since recent unpub- lished work indicates that extensive variations to flow depicted occur. Of special note is a relatively permanent easterly flow just north of 15* N indicatin g the existance of gyres in the northern half of the Caribbean. 39 FIG. 28 IN SITU DENSITY ENVELOPE - PESCA SERIAL STATION Lo 1.01 1.02 1.03 0 U) Ir w w 500 - z 0- 1000 40 13 0' 75' 70: 106 25 ZOO 46. C4) 15 03 20t 0\ FIG. 29 SUF@FACC CURRENTS 81 .4 4(+--oo-2 @04 4f4(--12 k 44 04-00 4(444 -.0.6 10* WrER TEO AW&WS N@INPERS(SrEWt PLp A.- .1 0'.. mll'ol@ AM li min 85* so* 75o 70 65* 6 25* 2.1 %b 4s A'p 20' I's AlL Nil 05 15* L A4*- FIG. 30 SURFACE CURRENTS 7 4*-08-12 <04 (14-OJB 44 lo* INTUOK)PTED ARROWS NONPERSISTENT UE@ Again, little data can be found specific to the site, or even the coastal waters of the Greater Antilles, but, of the observations made in open water (H.O. Pub. No. 700, Section I), up to 50 % may deviate from the expected westerly or northwesterly flow. Close to a land mass cur- rents usually parallel the coast, withan actual reversal of the open ocean current direction being common. it is expected that the surface flow will be easterly or westerly at the site, the division being about 50 : 50. Few subsurface current records are available. Figure 31 shows.twe current profiles near the site, unfortunately with no reference to the number of observations on which they are based. They indicate that large differences in direction with depth can be expected, with low speeds (variable in direction) at the bottom and up to I knot at the surface. Geostrophic calculations made using PESCA/CICAR data along 67' W (Figures 32 and 33) indicate that current reversals along the south coast of Puerto Rico may extend to 1000 meters, with surface speeds in excess of 2.5 cm/ sec ( 11 knot). This easterly flow is no doubt associated with the above mentioned gyre system. An attempt was made to measure deep currents at the Point Tuna/Yabucoa site during the survey described herein (Part II), however, attempts to recover the current meters placed at the site failed. 1.14 Nutrients As is typical in tropical seas the surface waters of the Caribbeai. are deficient in nutrient salts. They are removed from the photic zone by plankton which die and sink before all the nutrients can be recycled. A permanent and stable gradient in thi- thermocline at.shallow depths (30 - 100 meters) prevents recirculation of the nutrients to the surface waters once they are removed. As the plankton sink they are oxidized (decay) and return the nutrients to the deeper waters, thus below the euphotic zone nutrients are plentiful. Figures 34, 35 and 36 give the distribution of phosphate, silicate and nitrate with depth at the PESCA serial station. Note that maximums occur in the concentration of nutri- ents between 600 and 800 meters. The data in Figures 34 and 36 indicate that at this maximum the serial station molar nitrogen and phosphorus ratio is about 15 : 1 which is close to what is considered as the mean world ocean value of 16 : I which is the same ratio by which these ele- ments are taken up by phytoplankton (Sverdrup et.@jl,, 1942). At the Point Tuna OTEC site we have nitrogen data collected over one complete year which will.be discussed under the results of the cruises to that site. (See Part II of this report, section 11.5.2). From the above discussion we can see that the deep water ca *r be considered as an ideally proportioned fertilizer for planktonic growth. An OTEC plant with pumps cooling water from between 600 and 1000 meters will bring some of these nutrients to, or near, the photic zone where they might stimulate plankton growth. Our data on distribution of nutrients with depth allows us to calculate the enrichment of surface waters which might occur once the depth and OTEC plant pumping rate is 43 95* go, 85* 80* 75* 70" 65* 60* 1 1 1 1 55* 30* SPEED (KNOTS) SPEED JKNOTS) SPEED JKNOTS) 0.2 0.4 0.6 0.8 1.0 1.2 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.2 0.4 0.6 0.8 1.0 100 40 328 200 1 41 low 1 636 100 42 1 1 -320 e NE 200 --- 656 '00 1312 200 - 1-- 656 25* OW *NE NE tu- x 400 1312 Boo 262A 400 1312 OW C-MAR' 800 C'-';- 2624 1600 !tl- ft--A1241 SDO 2624 390 , A OCT zo* 1600 5248 1600 15248 40 i43 42 41 SUBSURFACE CURRENT PROFILES 15o 6 4400,t5 470 b 48* -40 5004 DE L 95. 90. 85* 80* 75* 70* 65* 60' 55* FIGURE 31 LOCATIONS OF SUBSURFACE. CURRENT PROFILES (FROM SP 189 U ............... 0 ......... 4:0 ............... 20 2 . ............ ........... ........... ........ .......... ......... ... ........... ........ 20 . ............ .......... .............. ... ............... .......... EST EAST ....... ........... ............... 5 10 ............. ............... ............... ............... .. .... 5 ............... ............ ............ ............ 500 ............ ............... Cn ............ ............... ............ ................ ............... 0 ............... w ....... ........ ............... ............... ............. ............. ................ ........... w ............... .............. ........... . ............... ............. ................ ............... ...... ............... ....... z ............... ................. ............... ........ .. ................. ........ .. .............. ................ ... ............... ............ Reference Level------------ .... ............. 1000 .......... ... ................ ... .......... ................ .... .............. ................ .... .............. ................ .... ............ . ................ .... .. ............ ................ ........ ...... ................ ....... .............. ...... ........ ................ ....... ............ .............. ........ ............... ................ ....... .............. 0 ................ ......... *.* ....... ................. ................. .......... ....... ...... ......... ............... ................ ............... ... ................ .......... ............... ................ ................ ....... ... FIG. 32 ........... ..... ....... ... ................. ........... .................. . ..... .... *- ...... . .... . ... ................. 1500 R/V CRAWFORD, CRUISE ................. ........... ................. ............ . . ............. JUNE 1972 .................. ................. ...... .......... ........ . ........ ........ .... .......... 0 @@@W E S T@ . . . . . . . . . . . . . . . . . . . . . . . . . ... .................. .................. ................... ... ..... ... 180 176 16* 150 140 130 120 110 GEOSTROPHIC VELOCITIES (cm/sec) FROM PUERTO RICO TO VENEZUELA ALONG 670W - 1@ Iq 14 9 1d 0 5 0 40-- 0 20 .... ........ ............. WEST 10 .......... .......... .......... .......... .......... ........... WEST 10 ............... 30- ............ 5 ........... ............ EAST ............ ............ 500. ........... .... ............... ............ ........... ................ ............ 5 ............ ............ ............ JX ............ ......... ............ .......... ............. ............... ............ w ............. 10 ............ W 5 0 .............. ................ 0 ............. ........... .......... ............. ................ ................ z ................ .......... ................ -----------Reference Level------------- .............. .............. 1000 ........... ....... .......... ....... ................. ....... .............. ........ ............... ........ .............. ............... ................ ........ ......... ......... .... ......... ............... ................. ......... w ................ ........... .......... ........ ........... ........ ............... ........... ................. .......... .................. ........... .......... .......... ......... ................ F I G. 33 ....... ........ ........ . ........ R/V CRAWFORD,CRUISE 72-27 ... .......... ................ ........... .......... I ...... .......... ................ ........... ................. ................ 1500'***'**'*"**'**-'*"* OCTOBER 1972 ..... ........ .... .................. ....I ...... *-**** .. ...... .......... ........... .................. ........... ............ ................. .. ........ ...... ........... .................. ........... .*.... ............ ................. .......I ......... ............ .................. ............ . .. ............ .................. ............ .................. .... .................. .................. ............ . ......... ... ........ ................. ......... .................. ............ ................... ............. ........................ ............ ............... ............. ................... .................. 180 170 160 15* 140 IY* 120 110 GEOSTROPHIC VELOCITIES (cmAec) FROM PUERTO RICO TO VENEZUELA ALONG 670W PHOSPHATE UGAT/L oe AL&, IV 9x xx j.,V, x FIG. 34 PHOSPHATE/DEPTH AT PESO OX X 20-0. R x ,yd" X SERIAL STATION XX, x xx X X-x x x x xx x x x x X x A X" X. X Xx x x X)t w it XX X x x .44, xv x )tw x 9. X. x Xx x x x x x X xt % x x E;eo . e, x x x x 9 x x 600 0 X X x x x x9 xx x XxX x x x XX x x 800. 0 x xxx x x x yxx x x x if x x 90o.e_ x @), x X0 X XX x @x xxx x x xx xx K "X xx 1, 2. 3. 4. G. 6. 7. e. 9. lo: 11. 12. 13. 1 1 G. 16. 17. i 2. 19, 20. 21, 22. 23 2-1. 2G. 26. 27.. 28. 29. 30. ........... SILICATE@JGAT/L 00. 0 FIG. 35 SILICATE/DEPTH AT:PESCA 2 00 . 0 SERIAL STATION AN x4, e 0 . 41 oo Ilk af LLI x X LLJ X A X ui 0 8001. 0 N:x X x 0.00. NITRATE YM 0 10 20 30 0 cr- 500- w w z x CL w a F I G. 36 NITRATE/DEPTH AT PESCA SERIAL STA. DATA FROM CICAR/CINTEX Il EXPERIMENT 1000 SEPTEMBER 1975 49 known. For each metric ton of water brought to the surface from 1000 meters into ideal photosynthetic conditions (i.e., 100 % conversion of nutrients), some 10 grams of plankton can be grown. This is unfortu- nately only possible in the surface layer of*the ocean, and it is inad- .visable to pump cold water into the heat source (see section 1.12). Some form of vast water management project could be undertaken, possibly@ to take advantage of the "free" nutrients., but it is very doubtful if such a pro .ect cap be realized when one considers that an OTEC plant pumping 500 Xsec of deep water can bring to the surface 43 million m3/day. This is not a lot compared to natural oceanic flows, it being equivalent to about 0.04% of the rate at which nutrients are carried by the Carib-,. bean Current in the photic zone. However, if this water were pumped into I meter deep ponds and held for only one week to allow plankton to bloom, it would require 320 sq. kms. of tank space. 1.15 Oxyaen Figure 37 shows the distribution of oxygen with depth at the PESCA serial station. Near surface values are close to 100% saturation while beneath the surface, saturation is always less than 100%. A-slight maxi- mum is observed at about 300 meters which represents water formed in the Sargasso Sea in winter (Kinard, Atwood and Giese, 1974). The oxygen minimum at 600 to 800 meters,corresponds.,to oxygen depleted by oxidation of planktonic detritus and the resultant maximums in nutrient concentra- tion mentioned under the discussion of nutrients (section 1.14). The deep water is high in oxygen reflecting the deep circulation of cold, oxygen rich polar waters. There is ample oxygen at all depths to sup- port all forms of marine life. 50 2. 3. .6. .0 OXYGEN ML/L 100.0- W@ A X 260-0- xu 300.0- A 4x@X ,400. 0@ FIG. 37 OXYGEN/DEPTH AT PESCA C;00. 0 SERIAL STATION w x W@X x 600-0- x z 'A xxAX;< X X g ;lJ N Z.@ x X x OW Q 700.0- xx x E300. 0 Xx A4 xx A, -A' x x 900.0- 1000.0 PART II: OCEANOGRAPHIC SURVEY OF POINT TUNA/YABUCOA SITE II.1 Extent of Survey A hydrographic and bathymetric survey of the Point Tuna/Yabucoa OTEC site has been made by the University of Puerto Rico Marine Science Department and the National Ocean Survey (NOS) of the National Oceanic and Atmospheric Administration (NOAA). The hydrographic data was all- collected from the University of Puerto Rico R/V CRAWFORD on four cruises in September 1975, January, March and May 1976. Preli minary bathymetric data'was collected from the CRAWFORD in September 1975, however, a -,om- plete survey was conducted by the NOAA ship MT. MITCHELL in March and April 1976 and has been compared to historical data collected previously from the NOAA ship WRITING. This bathymetry is discussed ir detail in iection 11.2 of this report. Table III lists the hydrographic stations occupied by CRAWFORD as well as their dates and positions. Figures 38 through 41 show the po- sitions of these stations at the site area. The prime prototype OTEC location is considered to be just off Point Tuna where stations 2748, 2793, 2825 and 2827 were located. This is due to the proximity of deep cold water close to shore (see Bathymetry in section 11.2). TABLE III OTEC HYDROGRAPHIC STATIONS OCCUPIED AT THE POINT TUNA/YABUCOA SITE Crawford Date Latitude Longitude Station Mo/Day/Yr Number Cruise # 1 2748 9/ 9/75 17058.3'N 65052,61W Sept. 175 2749 9/10/75 17050.5'N 65043.1'W 2750 9/10/75 17055.01N 65*45.8'W 2751 9/10/75 17059.5'N 65049.8'W 2752 9/11/75 17054.0'N 65052.0'W 2753 9/11/75 17048.21N 65051.21W 2754 9/11/75 17050.4'N 65056.81W 2755 9/11/75 17055.2'N 65058.2'W Cruise # 2 2793 1/ 8/76 17057.1'N 65052.1'W Jan. '76 2794 1/ 9/76 17053.8'N 65052.0'W 2795 1/ 9/76 17048.0'N 65051.4'W Cruise # 3 2825 3/11/76 17*57.5'N 65052.01W March '76 Cruise # 4 2827 5/11/76 17058.0'N 65052.41W May '76 2828 5/11/76 17049.01N 65051.01W 52 - ----- 18005' Pn ............ A.GUAYANES ............... . . exi. i*...i'-..........-...--...--....*.*..........,. ..................... PTA. YEGUAS 18000'N 2751 .. ............. TAJUNA PTAMENTO 2748 2755 2750 0 2752 17055' 2754 2749 -1705 2753 GRAPPLER BANK -17045' PPL 117040 66DOO'W 55' 50' 45' 40 35' 65030' FIG. 38-STATION POSITIONS FIRST OTEC CRUISE -SEPT. 1975 18*05 .......... PTA.GUAYANES PTA. YEGUAS 180 00' TA.TUNA PTA. VI ENTO 92793 17055' *2794 -17050 2795 GRAPPLER - BANK -17045 17*40 66000' 55' 50 45' 40 35 650301 FIG.39-STATION POSITIONS SECOND -OTEC C-RUISE--,JAN.1976 18005 P GUAYANES TA TA.YEGUAS p -18000, r 1A.TUNA PTA.VIENTO 92825 -17055' Ln 17 *5 0' GRAPPLER 17*45'- BANK 1 17040' 66*00' 55' 50' 45' 40 35' 65030' FIG-40-STATION POSITION THIRD OTEC CRUISE-MARCH 1976 18005 PTA.GUAYANES PTA. YEGUAS .......... .. ... 18000' PTA. TUNA PTA.VIENTO 02827 17055' Ln cr% 17 0 50' 2828 GRAPPLER BANK 1704.5 117 40 66000' 55' 50' 45' 40' 35 65030 FIG. 41 -STATION POSITIONS FOURTH OTEC CRUISE MAY 1976 11.2 Bathymetr The bathymetry of the southeast coast of Puerto Rico near the Point Tuna/Yabucoa site is shown in Figure 42. Contours are meters cot rected for the speed of sound in sea water according to Matthews (1939) Fras_@tto and Northrup (1957) indicate that depths east of here, near tb middle of the Virgin Islands Basin exceed 4,400 m and Stalcup and Met- calf (1973) 3how that the Anegada Sill, at a depth of 1960 m, is the controlling sill for this basin. Water in the Atlantic Ocean at this depth and near the Anegada Sill has a potential temperature of 3.60 C and originates in the surface layers of the Labrador Sea. Wright (1972 estimates an average production of 3.5 x 106 m3 sec -1 of Labrador Sea water. The deep water off the southeast coast of Puerto Rico is in direct communication with the Atlantic at depths shallower than 1960 m thus ensuring a virtually limitless supply of deep cold water to this area. Bathymetric profiles offshore from Point Tuna (A) and near Point Yeguas (B) are shown in Figure 43. Water deeper than 1,000 m (at a potential temperature of 5.2* C) is found 3.3 km from Point Tuna and 2.6 km from Point Yeguas. The Coast and Geodetic Survey chart #920 indicates that the bottoi in this area is hard and is composed of yellow clay, yellow sand, blue mud and coral. A gravity core taken off Point Tuna during this study consisted of coral sand with mud. 11.3 Temperature 11.3.1 Seasonal Variations Figures 44 through 47 are plots of temperature versus depty using temperature and depth measurements obtained from protected and unprotected thermometers during each of the four cruises to the Point Tuna/Yabucoa OTEC site. Figure 48 is a composite plot of the same thing for all four cruises. The plots show that the surface temperature varie from a maximum of 29.2"C in September 1975 to a minimum of 24.5' C in March 1976. By May 1976 the surface temperature had risen back up to 26.70 C. In contrast the temperature at 800 meters varied only from 6.5* C to 7.0* C and at 1000 meters was a constant 5.1 � 0.1' C. The A T between the surface mixed layer'and 800 and 100 meters varied as shown in Table IV. TABLE IV A T BETWEEN SURFACE AND 800 AND 1000 METERS FOR POINT TUNA/YABUCOA OTEC SITE Depth A T * C From Sfc. Meters Sept. '75 Jan. '76 March '76 May '76 800 21.8 19.0 18.3 20.2 1000 23.3 20.2 19.4 21.3 57 66* 65* 64PW 05' 18*N PT. Y 18*OdN PT. TUNA.""' 'B 00 00 0 55' %A rdoo A 000 is 0 is 00 5U I t fo 46 --800--- 0 KIL OW rERS -------- 10 1 40' rwodw 55' 5d 45' 400 0 FIG 42 Chart of the bathymetry in the western portion of the Virgin Islands Basin (hatched area in inset) southeast of Puerto Rico. Depth contours are in meters corrected for the speed of sound in sea water (Matthews. 1939). Data courtesy of NOAA, National Ocean Survey and from a bathymetric survey conducted during the present study. -200- -400- 600- Uj -800- -1000- -1200- KOO - -1600- -1800- -2000- 0 2 4 6 8 10 KM. BatHymetric profiles offshore from Point Tuna (A) and Point Yeguas (B) along lines shown in FIG. 43 Figure 1. Depths are meters corrected for the speed of sound in sea water and distance is kilometers. 41 1. 2. 3. 4. 6. 7. 6. 9. 10. 11. 12. 13. 14; 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 2B. 29. 30. 0 MW TEMPERATURE C KA X41 x 100.0- )ft x Wx OW x XOAlXX XX** x 200.0- AX .,x FIG. 44. 300.0- TEMPERATURE/DEPTH x xx U.P.R. OTEC CRUISE 1 1.x SEPTEMBER 1975 400.0- C, Goo.0- x x W Ac F- W E: LL! 700.0- x x x x 800.0- xx x x 900.0- x .1000.6 x 1 2. 3. 4. S. 6. 7. B. 9. 10. 11. 12. 13. 111. 15. 16. 17. 18. 19. 20. 21. 22. 23. 2,4. 2s. 26. 27. 28. 29. 30. .0 TEMPFRATURE C 100.0- x x x x x x x 4 x x x X X 2-00.0- x x x x x FIG.- 45 300.0- >c TEMPERATURE/DEPTH U.P,R. OTEC CRUISE 2 JANUARY 1976 )vx x SOO.0- x xx cy- 700.0- x x x 800.0@ xx 900.0- 1000. 4 14 4 1 1, 2. 3. 4. G., 6. 7. B. 9. 10. 11, 12. 13. ll. 15. 16. 17. 18. 19. 20. 21. 22, 23. 2,4. 25, 26. 27. 2e. 29. 30. TENPERATURE C x 100.0- x x x x x 200.0- x x x x FIG. 46 300.0- TEMPERATURE/DEPTH x U.P.R. OTEC CRUISE 3 MARCH 1976 x 500.0- eoo.o_ 900.0- 1000.D 4 @vl + 1. 2. 3. 4. S, 6. 7. 8. 9. lo.- 11, 12. 13, 14. 15. 16. 17. 1B. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 25;. 30. .0 T--l xx x TEMPERATURE C x x xx 100.0- x XX x xx x ,,X 200-0- x x X. 30010- x FIG. 47 x TEMPERATURE/DEPTH U.P.R. OTEC CRUISE 4 x 400.0- MAY 1976 x x r :@Oe. 0 600.0- x x 700.0- x eoo.o_ xx 900.0- x x X 1000.0 1 2. 3. 4. G. 6. 7@ 8. 9. 10. 11, 12, 13. 1-4. 16. 16. 17. 18. 19, 20. 21. 22. 23. 2-1. 25. 26. 27. @6. 29. 3e. T- F -7 ------1 !*---1 3w TENCERATURF C x Akx x xm x x x bk X -XV X 200,0- 14(hA 3001 41, FIG. 48 x X TEMPERATURE/DEPTH lleo. 0 COMPOSITE OF ALL U.P.R. OTEC CRUISES SEPTEMBER 1975 TO MAY 1976 SOO. R mix of TABLE V SUMMARY OF HYDROGRAPHIC STATIONS REPRESENTED IN TENP/DEPTH PLOT FOR HAWAII AREA Ship* Country Station Date Latitude Longitude Number D-M-Y HR Japan OC7 ll-IX-69 20059.0'N 154059.01W YQ USA HAH 31- V-66 22053.81N 158054.7'W YQ USA HAH 1-VI-66 24030.61N 161030.0'W CQ USA 004 2-VI-71 21029.01N 157003.0'W PI USA 0069 12- X-61 23030.0'N 160000.0'W PI USA P021 9-IX-61 23028.0'N 162056.0'W PI USA P028 10-IX-61 23056.0'N 167020.01W PI USA 105 6- V-63 25001.0'N 165001.0'W vi USSR 4317 2-11-59 20000.0'N 158009.0'W Ship's names represented by NODC code 65 The depth of the mixed layer varied from minimums of about 50 meters (in both September 1975 and May 1976) to greater than 100 meters (in March 1976). However, at no time was the water above 75 meters colder than 24* C and in May 1976, 24* C water was'available to a depth of > 150 meters. It is interesting to note the discontinuities in the ter[17-. perature/depth profile within the mixed layer or at the base of it. These are present in the plots for September 1975 and for January and May 1976. In September 1975 and May 1976 the dise@ontinuity indicates that the miyed surface water advecting into the area is gaining heat from radiant energy faster than heat is diffusing downward below 50 meters. By contrast, in January 1976 the surface mixed layer was losing heat to the atmosphere faster than it diffused upward. Apparently in March 1976 an equilibrium situation-existed. Figure 49 shows a vertical section of temperature versus depth for stations 2748, 2752 and 2753, taken in September 1975 (see Figure 38 for station locations). Except for minor transient variations it seems ob- vious that at any one time the temperature profile does not vary much from place to place within the site area. The isotherms in Figure 49 are, in fact, virtually horizontal. Below 1000 meters the site area has slightly lower temperatures than the Venezuela Basin since it is actually located in the Virgin Island and/or Whiting Basins where a deeper sill (Anegada Sill) allows colder North Atlantic Deep Water to flow into the area than into the Venezuela Basin. 11.3.2 Comparison to Hawaii Area Temperatures Figure 50 is a composite plot of temperature versus depth for the hydrographic stations listed in Table V. These stations are all in the vicinity of Hawaii and represent data taken in the months of February, May, June, September and October. Since Hawaii has received consideration as a potential OTEC site it seems pertinent to compare the temperature regime to the Puerto Rico site. This can be done by comparing Figures 25 and 48 to 50. Some general results of this com- parison are listed in Table VI. TABLE VI Parameter Puerto Rico Site Hawaii Area Surface Temperature 24.5 - 29.20 C 23.2 - 27.00 C A T to 800 meters 18.3 - 21.80 C 19.0 - 22.20 C A T to 1000 meters 19.4 - 23.30 C 19.7 - 22.90 C Depth of mixed layer 50 - >100 meters 50 - 100 meters 66 00 DISTANCE' IN KILOMETERS ro c%j to to r-- 5 10 15 c\j 0 -25 20 15- 500-- cn cr lo- w w z 0. 1000-- w 5 - 1500 FIG. 49 TEMPERATURE SECTION FOR OTEC CRUISE #1 - SEPT. 1975 mmi i 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11, 12. 13. 14@ -15. 16. 17. 13, 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. .0 I I" IX x I I I I x x x * x x X xx M TENFERATURE C xx x x xXx x X x X X x 100.0- XX X xx X x x x xx x x x x xx X 200.0- XX x x x x x x FIG. 50 x X TEMPERATURE/DEPTH 300.0- x x COMPOSITE PLOT FOR x HAWAII VICINITY STATIONS X x x x LISTED IN TABLE V 400.0- X x x x x X X x m X 00 x XX x F- XX x z 700.0- x x x x x eoo.o_ 900.0- X X x x x 1000.D X4 x The gradient oftemperature versus depth is somewhat greater in the Hawaii area down to about 700 meters and the temperatures at 800 and 1000 meters are respectively 4.2* C and 3.5* C compared to about 6.2* C and 5.1* C at the Puerto Rico site. 11.3.3 Diurnal Variations During the May 1976 cruise to the Point Tuna/Yabucoa site a survey of the diurnal variations in temperature was made to a depth of 750 meters using XBTs (expendable bathythermographs). 750 meter XBT probes were dropped every hour for a 24 hour period starting at 1650 hours on 10 May 1976. The XBT traces obtained are shown in Figure 51 in serial fashion. The figure has a common depth scale for all traces at the right. Temperatures may be read by orienting to the 20* C point indicated on each trace and using the temperature scale in the lower right corner of the figure (the scale is constant for the entire trace). Negligible variation is noted in the deep water except for slight changes which are associated with local shear and density gradients. These are scientifically interesting but of little importance to siting'an OTEC plant. Of more importance are variations noted near the surface. Tem- perature variations in the mixed layer were relatively insignificant with the surface varying only from 26.2* C to 26.8' C and the point just above the discontinuity being a constant 26.2* + 0.1* C. However, the depth of the mixed layer did vary significantly from a minimum depth of 40 meters to a maximum of 66 meters. This variation occurred on abouta 12 hour cycle (semidiurnal) and is probably tidal in origin. Throughout the di- urnal temperature survey water with a temperature of 24* C or higher exi.s- ted to a minimum depth-of 110 meters. The temperature at 750 meters was 7.0 + 0.2' C throughout the 24 hour period. 11.4 Salinity Figures 52 through 55 show the distribution of salinity with depth for each UPR OTEC cruise to the Point Tuna/Yabucoa site. Figure 56 is a composite plot of the same thing for all four cruises. These plots show essentially the same features as Figure 27 does for the PESCA serial station data except that surface salinities lower than 34.8 '/.. were not observed at the OTEC site. However, surface salinities of < 34.5 */oo probably occurred at the site shortly after the September 1975 cruise during October and November. Surface mixed layer samples col- lected at the PESCA serial station on 8 November 1975 had salinities of 34.030/oo to 34.04 0/.o. These lower surface salinities during the period of September to January are associated with seasonal discharge from large South American river systems, e.g. the Amazon and Orinoco (Froelich and Atwood, 1976: see also section I.11). Figure 57 is a temperature salinity (TS) plot for all UPR data col- lected at the Point Tuna/Yabucoa site. It shows the same features as the TS plot shown in Figure 24 for the PESCA serial station. The reader may refer to it and section 1.9 for a discussion of the water cores represented. The only notable difference between Figures 24 and 57 is the higher percentage of salinities > 37 */oo in the salinity maximum (SUW) 69 I A '-A A 1209 LOCAL TIME 1800 10 MAY 1976 0000 11 MAY1976 0600 12100 0 100 200 300 400 F- 500 600 FIG. 51 SERIAL PRESENTATION OF XBT TRACES TAKEN HOURLY ON 10 & 11 MAY 1976 . TEMPERATURE Is READ RELATIVE TO 20-C DOT ON TRACE AND SCALE. 700 800 25 I TEMPERATLi-RE IN *C 900 A4 34.0 0 36.0 37.0 38.0 X X x xxX SALINITY x x x 100. 0@- x xw 200.0- x X(X :fX 400.0- FIG. 52 SALINITY/DEPTH U.P.R. OTEC CRUISE SEPTEMBER 1975 IX It X 3F>. 0 36.0 37.0 38.0 X x x Ox SALINITY x x x 100.0- x xx xx X X XX 200-0- ox X x X X x x 300.0- x X X FIG. 53 *A x SALINITY/DEPTH U.P.R. OTEC CRUISE 2 500.0- JANUARY 1976 600.0- xX. 700.0- x eoo.o- X x x x 900.0- x x 1000.0 x 314.0 35. e 36. e 37.0 38.0 .0 x x SALINITY 95. x x 100.0- x x x x 200.0- x x x 300.0- x x FIG. 54 x SALINITY/DEPTH soe.0- U.P.R. OTEC CRUISE 3 MARCH 1976 x LJI F- L! 600.0- K z a- LIJ 0 700.0- x 800,0- x 900.0- x 1000.0 x A 34.0 35.0 36.0 37.0 38.0 1 .0 x x SALINITY 5r. x x 100.0- Xx x x x x X xx x 200.0- XX x x 300.0- x AM 0 x x x FIG. 55 GOO.0- SALINITY/DEPTH x U.P.R. OTEC CRUISE 4 MAY 1976 x x eoo.0 x1c 900.0- x X. 1000.k 3-4. 0' 3F@, 0 36'. 0 37. 0 38. 0 .0 '* ,, *. " " - IxI", X;@c Xx Z x x x OX x X SALINITY 7. x 01 x ioe.o- 4x XXX " xk x x xx X,;, x X W , x0 x )6 ox 200.0- x xx x X xx 300-0- wx 1100.0- @1000 FIG. 56 x xx x COMPOSITE SALINITY/DEPTH X9 ce x FOR ALL U.P.R. OTEC CRUISES u F- Lj: 600.0- K , X Z. x X 700-07 x X: )(N N AX )00. 01 xx X XX 1000.D X TF-Nr-'--RATUF,E- " C @ 1 @'-' 4'1 ",617 1 E3 -1-9 -0 21-2 23 24 21S 26 27 29 2930 0 1 2 3 4 5 6 7 PH 10 11 33 TS PLOT FOR STATIONS: 33.4 FIG. 57 2-748 TS PLOT FOR ALL 2749 U.P.R. OTEC CRUISES 2760 2761 2762 33.2 N.B. SALINITY VALUES 2763 2754 > 37.2% ARE NOT PLOTTED 276G '34 .2793 Z794 2795 2825 34.2 ZE327 2828 34, 6 -Poe 4::@z 36 .36. 2 set ..@cl. D 0 37 a at the OTEC site. This is due to two factors; (1) the OTEC site is some 90 miles closer to the origin.of the SUW water and (2) in 1975 and 1976 this water core generally exhibited higher salinities. 11.5 Nutrients During each UPR cruise to the Point Tuna/Yabucoa OTEC site sampleE were collected for phosphate, nitrate/nitrite and dissolved silicate. These were analyzed using the techniques described by Strickland and Parsons (1968) with modifications noted by Atwood (1974). The results of these analyses are represented in Figures 58 through 68. The pro- files are typical of those for open tropical seas and no major differ- ence from the results for the PESCA serial stations (described in sec- tion 1.14) were noted. In general all nutrients were quite depleted in the near surface or photic zone due to removal by plankton which are produced there. The nutrients are more concentrated at deeper depths where sinking plankton detritus decays releasing the nutrients to the water. Maximum nutrient concentrations occur at close to the same depths as the oxygen minimums (see section 11.6) reflecting the fact that the oxidation or decay of plankton partially depletes the oxygen at these depths as the nutrients are regenerated. The reader is re- ferred to section 1.14 for a discussion of biostimulation which might occur if these deep, nutrient rich waters are pumped to the surface by an OTEC plant. The following is a brief discussion of each of the nu- trients analyzed for 11.5.1 Phosphate Phosphate versus depth plots for each UPR OTEC cruise are shown in Figures 58 through 61, and Figure 62 is a composite plot for all four cruises. At no time did phosphate values above 200 meters, i. e., in the photic zone, exceed 0.3 11 M. Values were highest in the September and January cruises, but, were very depleted in the March and May cruises. In September near surface values between 0.20 V M and 0.25 p M were found at stations 2748, 2755 and 2754 (see Figure 38 for locations). This may be.due to some upwelling near shore and near Grap- pler Bank, however, neither stations 2751 nor 2753 exhibited similar high values. In January high values (0.20 - 0.25 p M) were observed at stations 2793 and 2795 (see Figure 39). In March and May most values above 200 meters were zero,i.e., readings were equal to or less than those for the reagent blank used in the analysis. Deep phosphate values were relatively constant throughout the year and most of the scatter below 300 meters in Figure 62 can be con- sidered as analytical variation, the precision of the analysis being less as the phosphate level increases. 11.5.2 Nitrate/Nitrite Due to the large volumes required, samples for nitrate and nitrite were collected only at the stations closest to Point Tuna (Sta- tions 2748, 2793, 2825 and 2827, see Figures 38 to 41). We regard this 77 2. 3. .,o @w x X 'AX X X PHOSPHATE UGAT/L 100. oam x A X x r< xx x 200.0- Y, x X x FIG. 58 x x PHOSPHATE/DEPTH 300.0- x x U.P,R. OTEC CRUISE I x x x SEPTEMBER 1975 3A X x GOO. 0 x 00 x x X XX x 600-0- x x z x x iE x 0- 700.0- x x X X XX doo.e- x xx x x x 900. O.L x xx 1000-a 2. 3, xx X x X X x PHOSrHATE UGAT/L x 100.0- x x xXX x x x x X x xxx x x x 200.0- x x >1 xx x XX x x X x 300.0- x FIG. 59 x PHOSPHATE/DEPTH x x X U.P.R. OTEC CRUISE 2 JANUARY 1976 x xx x 500.0- X x x F_ W 600.0- x x x IL U-1 700.0- x X x 800.0 xx x x 900.0- x x x cw# 3. PHOSPHATE UGAT/L i oe. FIG. 60 200. e*- PHOSPHATE/DEPTH U.P.R. OTEC CRUISE 3 300.0- MARCH, 1976 -100.0- QD 506.0- 600.0- z 700.0- 200.0- 900.0- t4 N '4 2. PHOSFHATE UGAT/L 100.01 ,7 'x 2oe.d:- x x F-IG. 61 PHOSPHATE/DEPTH 300-0- U.P.R. OTEC CRUISE 4 MAY, 1976 .100.0- x 600.0- Li 600.0- z :E 700.0- Boo. 0 900.0- looo.b 4m Aw No " x xx x xx xx X gwoxx x PHOSPHATE UGAT/L 100.019N. x xx Xx w x ox xXAX x x Xxx x x xx ),xx x xx x x x .. x x 300.0- x x x x xx x x FIG. 62 )o x X X x x PHOSPHATE/DEPTH X x COMPOSITE PLOT FOR ALL x x XX U.P.R. OTEC CRUISES YA xx x x x OD 500.0- x xx x xx x x x X X� x XX Ld x Ld 600.0- >c x )(Xx z X, XX x x 0 700.0- X>1 x X XX E300. 0 X X X xx x x x x X x x 900.0- >, x x x YA x XX 1000.6 x xx x x x specific location as the most favorable one for siting a prototypp, OTEC plant. Nitrate values were all < 0.05 p M and generally < 0.03 p M. High- est values were found at the bottom of the mixed layer or between 75 and 150 meters. The results for the nitrate analyses are given in Figure 63 for all cruises and a mean nitrate versus depth curve is drawn. The curve is very similar to that for the PESCA serial station data shown in Figure 36. Photic zone nitrate values at the OTEC site were lowest in the September and January cruises (0.2 to'1.5 ji M) and highest in May (I to 4'jj M) with March intermediate. This is opposite from the phosphate data which was highest in September and January and dep'leted in March and May. This would indicate that plankton productivity and/or upwelling are not the only mechanisms affecting nutrient concentrations in the photic zone. If these were the only mechanisms the N : P ratio would stay relatively constant. Comparison of Figures 62 and 63 shows that the N : P at the nutrient maximum is almost exactly 16 : 1 indicating that the nutrients in the deep water are ideally proportioned as a planktonic fertilizer (see sec- tion 1.14). II.'5. 3 Silicate Figures 64 through 67 show the distribution of dissolved sili- cate with depth for each of the cruises to the Point Tuna/Yabucoa OTEC site. Figure 68 is a composite plot for all four cruises. As with the other nutrients the distribution of dissolved silicate at the OTEC site is not basically different from that at the PESCA serial station (see Figure 35) and no significant variations were noted throughout the study. 11.6 Oxygen Figures 69 through 72 are plots of dissolved oxygen versus depth for each of the four UPR cruises to the Point Tuna/Yabucoa OTEC site. Figure 73 is a composite plot of the same data for all four cruises. The data is essentially identical to that sbown in Figure 37 for the PESCA serial sta- tion data. With the-exception of the slightly higher surface values ob- served during the May 1976 OTEC cruise very little variation in the oxy- gen profile is noted. There is ample oxygen at all depths to support all forms of marine life. The features of the oxygen profile as they relate to their causes arLd the water cores present is discussed in section 1.15. The minimum in the curve between 600 and 800 meters is also discussed under nutrients in sections 1.14 and 11.5 11.7 Geostrophic.Currents We have attempted to determine the aagnitude of near surface (upper 500 meters) currents at the OTEC site using the geostrophic method. The results of these calculations for Cruise No. 1 in September 1975 are 83 N03 CONCENTRATION IN YM 0 10 20 30 0 0 A STATION 2748 SEPT. 75 o STATION 2793 JAN 76 0 0 STATION 2825 MARCH 76 A STATI ON 2827 MAY 76 MEAN CURVE NO- vs Z 3 A 0 0 500- 0 w z m 0- w - FIG. 63 NITRATE/DEPTH, UPR-OTEC SURVEY COMPOSITE PLOT 1000- FOR ALL CRUISES SHOWING MEAN NITRATE 84 A C) L A 4. 15. 6. e 9- 10. 11. 12,- 13, 1,1. 16. 16. 17 19. 19. 20. 21. 22. 23. 2,4, 26. 26. 27. 28. 29. 30. T xw SILICATF UGAT/L mw x wx xx 100. 0 - *A xx 0., x 200-0- X @1:11x :mo. -0 X x x FIG. 64 X x SILICATE/DEPTH. -100.0- U.P.R. OTEC CRUISE 1 SEPTEMBER 1975 Goo. 0 x x x 600.0- X EL X 0 700.0- X x X X X 900.0- NX X x looo.b 2. 3. 4. G. 6. 7, B. 9- 10. 11. 12. 13, iq. 15. 16. 17. 10. 19*. 20. 21, 22, 23. 2,4. 25. 26. 27. 26. 29. 30. .0 T--T --- T--l x x xxxx SILICATF UGAT/L XX 100.0- *@x >ex xx* x >r ,X A X 200.0 x x x xx x x X X i Firi. 65 >,X SILICATE/DEPTH -100.0- U.P.R. OTEC CRUISE 2 JANUARY 1976 x X )k co 500. 0 a, x x L! 600.0- 1: x x z X 700.0- x x x eoo.o- x X 900.0- x x 1000. 0 I I i, , @A, @4) 1 1 2. 3. 4. G. 6. B. 9. 10. 11, 12, 13. Jd. 1G. 16. 17. 18. 19. 20. 21. 22. 23. 24. 26. 26. 27. M. 29. 30. ---I -T ---- 11 SILICATF UGAT/L x x 200.0- x x x x FIG. 66 400.0- SILICATE/DEPTH U.P.R. OTEC CRUISE 3 MARCH 1976 f@oel. 0 600. 0 (27, 0 . goo.oL .0 1 2. 3. 4. S. 6. 7. 8. 9. 10. 11. 12. 13. 1,1. IF-;. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. x SILICATE UGAT/L x X, 100.0- x X x x x x x x 200.0@ x x x x 300.0- x x FIG. 67 SILICATE/DEPTH x U.P,R. OTEC CRUISE 4 X MAY 1976 GOO.0- 00 00 x CK LL: 600.0- r- z 0- 700.0- eoo.o- 900. 0, x 10001 x M@w M M 1. 2. 3. 4. 6. 6. 7. 8. 9. 10. 11. 12. 13, 1-1. 16. 16. 17. 1 e. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. .0 -a-v@x x XMWXX X x SILICATE UGAT/L W.0 xg x x 100.0- *"If xx x Y.OXX x x x ltx xx xx xX 200. 0 x @% X, j x Xx M x 300.0- x FIG. 68 >I(xxx X x xx SILICATE/DEPTH xxxygxA x 400.0 x COMPOSITE PLOT OF ALL x x U.P.R. OTEC CRUISES x x Y@ x x X SEPTEMBER 1975 TO MAY 1976 00 500. 0 x x x x X xx x x x x x X x x 600.0- x N z x x x x X x (L x 700.0-' x x x X x x x E300. 0 x x X X x x x X x X x x x 900.12@ x x x x x X X iooojb x x x 6. .0 X X KxW X >WW x x xc.,4k>, OXYGEN ML/L x x Am x @)ox Ax* )ou 200.0- x 300.0- )K4 x X 400.0 x soo.0 xx x FIG, 69 x OXYGEWDEPTH 600-0- 4x A U.P.R. OTEC CRUISE 1 )e SEPTEMBER 1975 x X CL 'x 700.0- x x x X X eoo.o- x X X X 900.0- X 4 10001 jA 2. 3. 4. 6. .0 *x OXYGEN ML/L 100.0- x x x x x x 200.0- >( xt x XX il x 300.0- x x 400. e FIG. 70 OXYGEN/DEPTH *X U,P..R. OTEC CRUISE 2 JANUARY 1976 600. XX t iL 700-0- x Goo.e- x x 900.0- x x x OXYGEN NL/L. 100.0- 40o.e- Goo. 0 FIG. 71 OXYGEN/DEPTH U.P.R. OTEC CRUISE 3 MARCH 1976 600.0- z T LL2 700.0- eoo.e- x 900.0- x 000. OXYGEN ML/L x X -6-02 200.0- FIG. 72 OXYGEN/DEPTH Uk U. P. R. OTEC CRU I SE 4 MAY 1976 Ul 920 0 2. 6. xx .0 x woo" x x x )0*#kx A OXYGEN ML/L x x x x x XA: x xx x 200.0- 'A "'Ix x X 300.0- ,'A X X X 500.0- FIG. 73 'A A V x, )(x OXYGEN/DEPTH IX x XX a, COMPOSITE OF ALL U.P.R. OTEC CRUISES 600.0- x SEPTEMBER 1975 TO MAY 1976 z mr F- XX 700.0- x X w x X 800.0- X x XX x x x X 900.0- xx x x x X. X 1000.6 x given in Tables 7 and 8 (see Figure 38 for station locations. Unfortu- nately the geostrophic method is most suited to the study of meso-scale circulation, and is at its limits of accuracy when stations are only 20 km apart, so the results of the calculationi presented in Tables 7 and 8, should be interpreted with caution. (Note that the zero velocity at 1000 meters is an assumption necessary for calculation, and is not an obser- vation). TABLE VII GEOSTROPHIC VELOCITIES AT THE YABUCOA SITE CRUISE # I (See Location Map- Fig. 38) Distance between 2751 and 2749 = 20.21 km Mean latitude = 17.91 Maximum depth is at Station 2749 and is 1000 meters. Dynamic heigbt dif- ference between Station 2751 and Station 2749 is -0.019 dynamic meters at 1000 meters Depth Volume Velocity Volume Z Transport at Z Transport above Z Z2-ZI 0 0.00 -21.0 5.0 -0.14 - 7.7 -0.14 C.03 100 -0.12 13.2 200 0.07 5.5 300 0.18 5.5 0.10 400 0.28 4.4 0.04 500 0.33 - 0.0 -0.03 600 0.30 - 3.3 700 0.21 - 5.5 -0.09 -0.09 800 0.12 - 3.3 -0.02 900 0.09 1.1 0.01 1000 0.11 0.0 Meters Megatons/sec CM/sec Megatons/sec Note positive values denote westerly flow and negative values easterly flow 95 TABLE VIII GEOSTROPHIC VELOCITIES AT THE YABUCOA SITE CRUISE # 1 (See Location Map, Fig. 38) Distance between 2748 and 2753 = 19.04 km Mean latitude = 17.88 Maximum depth is at Station 2753 and is 1000 meters. Dynamic height dif- ference between Station 2748 and Station 2753 is -0.036 dynamic meters at 1000 meters. Depth Volume Velocity Volume z Transport at Z Transport above Z Z2-Zl 0 0.00 -42.2 -0.26 50 -0.26 -11.7 0.02 100 -0.24 15.2 0.35 200 0.11 21.1 300 0.43 12.9 0.32 0.20 400 0.63 8.2 0.16 500 0.79 8.2 0.15 )00 0.93 7.0 0.09 700 1.02 2.3 800 1.08 3.5 0.06 0.06 900 1.13 2.3 1000 1.16 0.0 0.02 Meters Megatons/sec CM/sec Megatons/sec Note positive values denote westerly flow and negative values easterly flow Both calculations show an eastwards flow at the surface over a slow subsurface westwards flow, degenerating to random noise at 500 meters, below which depth the values are -,ieaningless. About all that can be said is that at the time of the survey easterly surface velocities in the or- der of 1/3 to 1/2 knot were indicated between 0 and 50 meters with a reversal at about 100 meters to westerly flow of less than 1/3 knot. Since the stations were taken over a three day period this is an "average" condition. 96 PART III: CONSIDERATION OF OTHER SITES NEAR PUERTO RICO Prior to submissi"on of our original proposal and during the histori- cal data survey reported herein we considered other possible OTEC sites near Puerto Rico with the conclusion that the Point. Tuna site was the best site oceanographically. One other site which has some merit is off the Northwest coast of Puerto Rico near the town of Aguadilla. and. the inactive Ramey Air Force Base. Due to the real. estate available at Ramey this site could have potenials other than strict oceanographic ronsidera- tions. The following are some comments pertinent to this site. (i) Bathymetry. In general the west coast is shallow and only at Aguadilla does a deep tongue protrude shoreward. Even so, depths of 1000 meters are only found 10 kv (6 miles) NW from shore. (C & GS Chart 920). (ii) A T Profiles. Little temperature data is available, tut the south coast is likely to have both a more fa,.7o*rab".e surface water and a better rate of change of temperature with depth because of the geostrophic, tilting effect. men- tioned in this report (sections I.10 and 1.13). Fialure 74 compares A T profiles off the South coast and off Aguadilla for comparable times of year. (iii) "Accessibility in all weathers" is doubtful. Quoting from the Environmental Guide for the Mona Passage Area by NOAA, June, 1974, "Moderate or rough,seas also devei_@Tat times in winter when the northeast trades become stronR. There is a considerable increase in swell during the period De- cember to March, due to the increased strength of the north- east trades at Lhis time of the year. This is the season of 'rollers' when series of huge swells are liable to appear at any time. The rollers are very probably caused by gales further north over the Atlantic." (p. 14) "Waves of 20 feet or more have been observed for all months." (Op. cit. p. 25) (iv) Oceanographically the Yabucoa site is more favorable. A short term advantage in terms of ready-to-use housing may be available at Ramey, but, if t't-e plant is designed xo serve for fifty to one hundred years, such considerations are minor 97 ,Op, TEMPERATURE OC 5 10 15 20 25 0 CRAWFORD STATION NO.2652 .29 MARCH 1973 17'P 4 VN 66* 56'W cr w w m z500- KNORR STATION NO. 457 4 MARCH 1974 18c' 27.51 N a. 670 25.6'W w 10001 FIG. 74 TEMPERATURE PROFILES 98 PART IV: COMMENTS ON TRW SYSTEMS LIST OF DESIRABLE CRITERIA FOR AN OTEC TEST SITE During the May 1975 OTEC workshop in Houston,Texas, TRW Systems presented a series of criteria they felt were essential for an OTEC test site. (Proceedings 3d OTEC Workshop, Houston, Texas, May 8-10 1975). We feel it pertinent to a consideration of the Puerto Rico site that these cHteria be discussed in reference to the Puerto Rico site itself. Fol- lowing are the TRW criteria with a discussion of each with reference to the Puerto Rico site. 1. A T profile for plant operation all year Almost any site deeper than 1000 meters around Puerto Rico will. provide a A T of 20' C (36' F) between 1000 meters and the surface. Some sites can do better than this as we have shown for the south coast. 2. A site representative of an open ocean water mass: a) minimal run-off Puerto Rico has no great rivers, and the run-off from the existing rivers tends to remain close to shore until it mixes out. Any site around Puerto Rico fulfills this re- quirement if it reaches 1000 meters. On the south coast there is very little run-off. b) biologically, chemically and physically similar to open ocean As we have shown, there.are really four water masses to be considered, not one, as the TRW list implies. Both the historical data (Part 1) and the Point Tuna/Yabucoa data (Part II) show that any site around Puerto Rico that is more than 1000 meters deep will fulfill these requirements. 3. Availability of water mana@ement capabilities of the intake/ output to test possible effects and uses such as mariculture. Fr.om our discussion of nutrients and density the possibil- ity of mariculture seems to be somewhat questionable since it is advisable to let the outflux sink to avoid cooling the surface supply of hot water. However, if systems can be designed that Would not interfere witY plant operation, there is a vigorous program of aquaculture at the Univer- sity of Puerto Rico; land based but capable of being re- directed. .>There is a second vigorous mariculture program at the Lamont Laboratories at St. Croix-, Virgin Islands. 4. Access in extreme conditions "Extreme conditions" around Puerto Rico means hurricanes and there will be no access. The south coast is more sheltere'd than the north coast, however, see both "waves" in section 1.8 and our comments on the Aguadilla site. 99 5. Access roads to construction sites,, airports) deep water port Puerto Rico has an adequate road system that handles heavy truck traffic both for the sugar cane industry and the containerized cargo of Puerto Rico Maritime Authority. This net extends throughout the island and passes close to any construction site imaginable. There are adequate air- ports in Roosevelt Roads Naval Base, San Juan, Ponce, and Aguadilla which handle heavy jet traffic (including Boeing 747s and Lockheed 1011s in San Juan) and smaller airports in Mayaguez and Arecibo and other island cities. There is a deep water port adjacent to the Point Tuna site at Yabu- coa which commonly handles 600 foot tankers. There are also deep water ports at Roosevelt Roads Naval Base, San Juan, Mayaguez, Guayanilla and Ponce. 6. Adequate power, housing and transport facilities The western end of Puerto Rico is supplied by the 115 KV island-wide grid. Housing, if for more than 100 men will probably have to be constructed, but it can be prefabricated or constructed very cheaply on the site due to the mild climate requirements and utilizing cheap concrete housing techniques which Puerto Rico pioneered. Transport facili- ties in Puerto Rico are adequate (see access roads above) and include the Puerto Rico Maritime Authority ships and an adequate supply of containerized vans and tractors, air freight companies that work with both jet and propeller driven aircraft, and excellent seagoing tugs. Two active cement companies exist (Ponce Cement and San Juan Cement) and are presently supplying cement for up- dating Puerto Rico's highways into a modern four lane freeway system. 7. University interest with an active and adequate computer facility The University of Puerto Rico has a department of Marine Sciences and Engineering Faculty with an active interest in the OTEC plant. The Mayaguez campus has a PDP 10 com- puter with about 150 K core, three disk drives and four magnetic tape drives-the installations replaced an IBM 360. The Engineering Faculty has a Digital PDP 11 and the Marine Sciences Department has a small 12 K PDP 8 computer at its La Parguera Marine Station. 100 PART V: CONCLUSIONS 1. A survey of historical oceanographic data for the area south of Puerto Rico shows that the temperature profile there is excellent for OTEC exploitation. The A T to 1000 meters is about 24' C (43' F) in September and October and always < 200C (360F) . This has also been confirmed at a specific site off the southeast coast of Puerto Rico (just off Point Tuna and Yabucoa) during four separate hydrographic cruises during the period September 1975 to May 1976. 2. The continental slope at the Point Tuna/Yabucoa site is very steep and water depths of 1000 meters exist within 1@2 miles of shore. Thus, the site is very suitable for a floating prototype plant tied to the Puerto Rico power grid by direct lines. 3. Due to geostrophic conditions in the Caribbean the warm mixed layer at the Point Tuna/Yabucoa site is generally quite thick and geo- strophic calculation of currents at the site indicate that surface flows in the order of about 1/3 of a knot exist. Thus an OTEC plant is insured a plentiful supply of warm water for its boilers and proper engineering should easily avoid short circuiting the A T. 4. The supply of cold deep water at the site for the cooling cycle is virtually limitless. 5. The site is-protected from north and northeast swell and a mild .sea state exists all year round except for hurricanes. There is adequate access for constructing and servicing of a floating OTEC plant. 6. Adequate shore based facilities such as deep water ports, ac- cess roads, transportation facilities, housing, cement supply and air ports exist adjacent to, or near to, the site to allow for constructing and servicing of either a floating or shore based OTEC plant. 7. The salinity, temperature, nutrient distributions at the site are typical of an open tropical ocean even though the site has deep water within 11.1 miles of shore making the site ideal for a prototype OTEC plant. 101 PART VI: SEMINARS PRESENTED BY UPR OTEC PROJECT STAFF Ocean Thermal Energy Conversion - Presented to Department of Marine Sciences Seminar, August 1975. Ocean Thermal Energy Conversion - Presented to NOAA Atlantic Oceanographic and Meteorological Laboratory, Miami, March 1976. Ocean Thermal Energy Conversion - Presented to Puerto Rico Colegio of Engineers, April 1976. Ocean Thermal Energy Conversion - Presented to International Friendship Club of Mayaguez, P.R., May 1976. 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