Studies of the California Current System

STUDIES OF THE CALIFORNIA CURRENT SYSTEM

bY JOSEPH L. REID, JR., GUNNAR I. RODEN, and JOHN G. WYLLIE

Contributions from the Scripps Institution of Oceanography, New Series No. 998 ILLUSTRATIONS

Figure Page Figure 1. Avernpe monthly atmospheric stw level pressure ovrr the e:istrrn North Pacific Ocean :ind tlic western coast of Sorth .iineric:i (luring four niiinths of tlir year____ 2!) 2. Variations of wind sl)c,ed with distance from coast, hIay, 1963 ___-______-____ 30 :<. Ocean currents off the western roast of Sorth ,\nic,ric*:i 3% 4. Ocean ten1per:iture :it 10 nirters, August, l!).;: :nit1 AIarcli (com1)osite) ______:G r). Vertical I)rofiles of temprr:itiirr, s:ilinity, osygrn. :inti phosphate from the sarfnce to 600 nirters, Aiignst,

1!).7.7 ______~ _-__----- ____--__ __-_ --______- ____ :xi G. Seasomil ynriation of temperntiire in the ii1)prr 15 - nieters :it four lorntions______40 t. Sr:ison:il v;iriation of trrnper:itnre :it the se:i siirf:iw off the western coast of Sorth Amrric:i______-41 S. I*'rrcliienry tlistribiition of monthly nvcw~pt, trwi1wr:i- tiire. Scripps I'ier, l!)li-N______-______41 9. AIonthly nvernge trmprraturr :it Sorth Far:illoii 1sl:intl in 1940 and 19K_...... ______42 10. Salinity at 10 nieters in August, 1955, March (coni- posite), .January (average of three years), and Jun~ (average of three years) ...... ____ 4.3 11. Seasonal variation of salinity in the upper 125 meters at three locations...... __ 4: 12. Seasonal variation of salinity at the sen siirfnre off the western coast of Xorth Xmeric:i ______46 THE WINDS OVER THE NORTHEASTERN PACIFIC OCEAN AND THEIR EFFECT UPON THE WATER The most important force moving the surface waters of the ocean is the wind. Upon comparing a current chart of the North Pacific Ocean with a chart of the winds, one is iinmediatrlg striick by the sinii- larities in direction of niotioii. Tlic strong westerly winds in high latitudes iiiow the, watw (wtivar(1 ancl the strong ancl coiistniit trade, wiiitls f;irtlier sontli push the water westwartl. Ihth tlit. iviii(1s ;iird the water go through an enoriiioiis clockwise c*irc.iilatioii in the North Pacific (Icean. Tli~C'al iforilia ('iirwiit lies at the eastern, soiitli\v;irtl-flo\\.iiip sitlv of the circulation. The circulation is of coi~rscIiot cliiitc so siiiil)l(~as this. Tlirre arr c'oiiiitrrciirrc,iits aiitl su1)siirf;ic.c. rui-- 50" N

40"

30"

20" 150"w 140" 130" 120" 1 10"

FIGURE 1. Average monthly atmospheric sea level pressure (in millibars) over the eastern North Pacific Ocean and the western coast of North America during four months of the year. FIGURE 2. Variations of wind speed with distance from coast, May 1953. Measurements made along Station Lines 80, 100, 120, and 137, on CCOFI Cruises. Wind expressed os meters per second. Stronger: winds occur off Point Conception.

THE CURRENTS The. Califoriiia Current tern is a part of the grwt clockn isc circulation of the Korth Pacific Ocean. .\t high Iiititud(>\ the. 11 aterr; move eastward under the iiifliieiicc of the strong westerly Jviiids (the “roar- iiig forties”) aiitl near the roast of North America diritlc iiito two braiiehes. The siiialler part turiis iioi*thward iiito the Gulf of Alaska, aiid the larger part tiinis southeastward to become the California Current. 111 geiieral the temperatnrcs in the opeii oceaii are lower toward the iiorth so that the branch turiiiiig northward into the Gulf of Alaska is knomii as a wariii cnrreiit. The ivater which is brought south by the California Current system is cooler than the waters farther offshore. As it moves slowly south at \pwdx g(1iicXrally less than half a knot it becomes \variwr niiclcr the iiifliieiice of the suii and by mixing vith the. wariiier waters to the west. As it nears the latitude of 25’ r\’ it bcgiiis to turii westward and its u-aters becoiiie part of the west-flowing North Eyua- torial C‘nrrciit. On the inshore side of the current soiiie disturbaiices in the circnlatioii are found. 11 sinal1 eddy is iisilally fouiicl offshore from Cape Plleiiilociiio through most of the year (Fig. 3a). A similar cddy is foiiiitl between Guadalape Islaiid aid the iiiaiiilaiid. A periiiaiieiit eddy, the Southern Cali- foriiia Couiitercnrreiit (Sirerdrup aiid Fleming, 1941), is fouiitl iiisicle the subnierged peiiiiisula that estriicls sonthcast from Point Coiiceptioii and iiicludes PROGRESS REPORT. 1 JULY 1956 TO 1 JAR’CARY 1958 31 Santa Rosa Island, San Nicolas Island, and Cortes measured at the points indicated. In order to express Bank. The waters on the eastward side of this are these density distributions as currents it is necessary protected from the northwest winds by the land and to make certain assumptions. These are that the cur- separated in part from the strong southeasterly-flow- rents and density distribution are steady, there is no iiig offshore current. The currents are weaker and effect of friction either at the bottom or from wind usually to the north. The waters remain off the coast at the surface, there is some depth (perhaps 1000 of southern California for a considerable time and meters) at which there is no motion and to which become much warmcr than those offshore, which are the density measurement can be referred, aiid above constantly replaced by cooler water from the north. this level all movement is horizontal and east-west. The area off southern California was studied by These assumptions are no doubt best fulfilled farther Sverdrup and Fleming (1941) using the data taken upstream where the west wind drift at 160” W longi- by the California Division of Fish and Game vessel tude is very nearly east-west and where the ocean Blziefin in the late ’30s and the University of Cali- is deep. At any rate the currents computed from the fornia vessel E. W. Scripps in 1940 and 1931; and density distribution in that area have been in agree- until the CCOFI program began it was the only area ment with the many nieasurcments made by the set which had received any detailed attention. The small and drift of mrrchant vessels (university of Califor- area covered by these cruises made speculations about nia (in press) and U. S. Hydrographic Office, 1947). the continuity of the iiorthward flow around Point Offshore in the California Current system these Conception extremely difficult. Only one extensive measurements are equally in agreement with the set cruise was made from Punta Eugenia to Cape Men- and drift results and present a coherent picture of dociiio. As this was conducted in the summer of 1939, the clockwise circulation of the North Pacific. Near it did not bear upon the problcni of the continuity of the coast, however, the assumptions are riot so well the wiiiter c.outiterciirreiit. However, many of the re- fulfilled. The eff’ect of the irregular coastliiir cannot sults of the CCOFI program in the regions where be entirely ignored, nor the varying depth. These and Srerdrup and I”1eining had little or no data had been the winds, which sometimes reinforce and sometimes anticipatcd to a remarkable dcgree by their specula- oppose the current, aiid the sigiiificaiit yertical motion tions. in the regions of upwelling and thc oscillations of A deep countercurrent, below 200 meters, flows to internal wares (Reid, 1956) all conibiiie to make the the iiorthwest along the coast from Raja California measurement of currents by density distribution less to some point beyond Capr Mendocino. It brings accurate and less useful. warmrr, more saline water great distances northward The currents computed from density are less clear along the coast. When the iiorth winds are weak or near the coast (Fig. 3). Indeed it is not upon the absent in late fall aiid early winter the couiitrrcurrciit density measurements alone that our knowledge of forms at the surface well 011 the iiishore side of thr the countercurrent is based, but upon the observed main strcain and exteiids from the tip of Baja Cali- effect of the countercurrent in moving large quantities fornia to iiorth of Point Conception, where it has of water of a distinct type far up the coast, and upon been called thc Davidson current. The causes of the various direct measurements obtained by drogues, cte~pcountercurrelit and its appcarance at the surface drift bottles, and an electronic current-measuring in- in winter are not undrrstood. Rossby (1936) derived strument, the Geomagnetic Electrokinetograph (von a theory of oceanic circulatioii in which a large ocean Arx, 1950). currrnt has associated with it on its lefthand side Because of the doubtful validity of computing cur- lool~iiigdownstream a countercurrent ; and Sverdrup rents from density in the nearshore regions, especially et al. (1942) mentioned the possibility that the Cali- around the Channel Islands, work was done as early fornia Current system is an example of this sort of as 1937 with drift bottles (Tibby, 1939) and in 1950 circulation. However, the assumptions are not all with drogues. The density distribution indicated a fulfilled and this theory cannot be applied with any movement to the northwest inside the islands. Meas- coiifidence at present. urements of the currents made at the same time (in The process of upwelling, in which winds parallel June 1950) by both the density method and drogues to the coast move the waters offshore, has been men- showed a northwesterly flow. Whether this flow tioned. This effect seems to be intensified south of reached as far as Point Conception and proceeded capes and points which exteiid ou‘t into the stream. iiorthward around the Point in summer has been more Thus Cape Mendocino, Point Conception, and l’unta recently inquired into by using drift bottles. These Eugenia are regions of more intense upwelling than hare been put over on all the CCOFI cruises made in the rest of the coast. the last three years. The results have been very in- Some of the current measurements made by the formative. They have indicated a flow northwestward CCOFI program are shown in figure 3. They are com- from the Channel Islands region around Point Con- puted from the density distribution of the water, ception oiily in late fall and winter. In summer the "') .)-

I 50" 140" 130" 120" 110"

cI25 120" 115" 110"

FIGURE 3. Ocean currents off the western coast of North America. (a) Surface current, August 1955, dynamic height anomalies, 0 over 1000 decibars, contour interval, 0.10 dynamic meters; (b) Surface 35 35" current, November 1952, dynamic height anomalies, 0 over 500 decibars, contour interval, 0.05 dynamic meters; (c) Surface current, March (composite). dynamic height anomalies, 0 over 500 decibars, contour interval, 0.10 dynamic meters; (d) Current at 200 meters, August 1955, dynamic height anomalies, 200 over 500 decibars, contour interval, 0.05 dynamic meters; (e) Current at 200 meters, March (composite), dynamic height anomalies, 200 over 500 decibars, 30" contour interval, 0.05 dynamic meters; (f) Current in December 1954 as determined by three methods-from density distribution, drift bottles, and Geomagnetic Electrokinetograph (GEK).

30" 25 PROGRESS REPORT, 1 .JUI,Y 195G TO 1 JANUARY 1958 33

l5U" I4V 130" I LO" I I

6 I I , 1 I 150" 140" l30^ 12v I drift bottles have moved short distances northwest- the Subarctic water mass. This water has remained uard along the coast betwern Sail Dicgo and Port in the central part of the North Pacific gyral long IIueiieine but none has rounded the corner. There is enough for its temperature to be raised, its salt con- reason to believe that they turn southward again in tent to be raised by evaporation, and the nutrients in summer as they near the Point aiid are carried down the surface layer nearly exhausted. These two bodies with the main currcnt. An interesting feature of the of water move eastward side by side until they ap- drift bottle results is that few of the bottles put over proach the coast of North America. Some mixing more than 40 miles offshore have returned to the takes place as they move to the eastward, though the coast. This result is consistent with the assumption boundary still remains relatively sharp. But as the that the surface waters are nearly always moved Subarctic water turns southeastward to become the slightly offshore by the prevailing winds. California Current much more horizontal mixing takes The currents were measured in Dcceinber 1954 by place near the surface. This continues down the coast the distribution of density, by drift bottles, aiid by so that the upper waters have attained quite different means of an electronic current-iiieasuriiig device (Fig. characteristic values by the time the Current begins 3f). The three methods are in gcliieral agrecincnt, all to turn southwest. The mixing does not take place of them shou ing a northwestward flow past Point cqually at all levels but is most intense near the sur- Conception. The electronic measiiring instrunleiit has face., so that the upper waters come to be domiiiated revcalcd many short-period changes in the surface more nearly by the Central Pacific characterist:cs currents OFCalifornia (Reid : in press). Some of these than do the waters below 100 meters. This effect will variations appear to be tidal. Thme is so much varia- be shown later on vertical profiles. tion over a 12-hour period that a single ineasureinent is difficult to interpret. A clearer picture is found From the South when some averaging system is introduced either by To the far sonth lies a great body of water called area or by time (Knatuss and Reid, 1957). Equatorial Pacific, which has been defined by a certain easily recognizable temperature-salinity relation. In the upper levels these waters are very warm and THE NATURE OF THE WATERS salty. The major influx of these waters into the Cali- ENTERING THE MAIN STREAM fornia Current system occurs along the coast well The waters of the California Current come from beneath the surface. At the tip of Baja California the four water masses distinguishable by their content of temperatnre-salinity relation below 200 meters coin- heat, salt, oxygen, and phosphate. (The deeper circu- cides with that of the definition of Equatorial Pacific lation is excluded froin this discussion.) Processes of water. This water also fills the lower levels of the Gulf mixing and surface effects cause these properties to of California. The water which moves up the western change as the water inoves. We shall identify them by coast of Raja California at depth must have been their descriptions as they enter the area of interest. beneath the surface for a long period because it is low in oxygen and high in phosphate. This implies a From the North great deal of decompositioii of organic matter fallen A great part of the water mass which nioves east- from the surface, and no extensive mixing with the ward across the North Pacific has been called Sub- surface waters. arctic water. At 147" W longitude this eastward- From Below moving mass is centered at about 48" N latitude in summer. It is this water mass which gives to the off- The strong northwesterly winds near the coast of shore waters of the California Current their charac- the Californias combine with the earth's rotation to teristic surface properties of low temperature, low effect an offshore transport of the surface waters. salinity, high oxygen and, in part, their high phos- These are replaced by colder, more saline waters from phate. These properties distinguish this water mass below. Having been below the surface for a long time, sharply from the waters to the southwest with which the water thus upwelled contains nutrients which have it mixes as it moves down the coast of North America. been both produced iii it by decay and by mixing with Mixing alters the properties of the Subarctic water the still richer, untapped reservoirs below. Some part considerably before the Current begins to turn south- of these upwelling waters conies from the lower levels west at about 25" N latitude. Rut it is still clearly rec- of Subarctic water and' some parts are a transitional ognizable, especially by the low salinity, as it turns form of the Equatorial Pacific water which has flowed westward and becomes part of the North Equatorial far up the coast beneath the surface and mixed with Current. the lower levels of Subarctic water. The wind charts (Fig. 1) have shown that winds From the West are more likely to cause upwelling in spring and early In the central part of the North Pacific lies water summer but that there is some tendency for upwelling whose properties are in sharp contrast to those of at other times of the year. The predominance of the wind from the northwest even ~vlieii weak and the general sonthcastwrd movement of the ciirrent coni- bine with the irregularities in the sea bottom and with such sharp breaks in the coastline as Cape Mendocino, Point Conception, and I'luita Eugenia to cause spots of cold, salty water near thc coast through a great part of the year though, as will be seen, spring and early biiinnier are the periods of strongest upwelling.

RESULTANT DISTRIBUTION OF PROPERTIES AND THEIR VARIATION WITH SEASON The properties of the water are shown by the horizontal charts aiicl yertieal profiles. Some have smooth patterns, some change abruptly, some are character- ized by niaxinia and minima which appear as tongues or fingers penetrating other waters.

Temperature In general ocean temperatiires become higher toward the equator and lower toward the poles. Over most of the Pacific Ocean the lines of constant temperature run east-west. The clockwise circulation of

150 14W 130 I20 ll@1

I50 I40 I30 120 I I0

20 ,,,1/,1,1/11,1,,, ,, j,, 20

FIGURE 4. Ocean temperatures at 10 meters (degrees Centigrade). (a) August 1955. (b) March (composite).

The great eddy off southern California results at this time of year in a local high temperature between San Diego and Sail Clemente Island. This water is nioviiip very slowly to the northwest aiid is warmed to their high temperatures as it moves. Four profiles of the Tipper 600 meters of water drawn roughly pcrpendicular to the direction of flow are showii in figure sa. The high temperatures at the surface diminish very rapidly with depth and at 600 36 CALIIWRSIA COOI'ERATIVE OCE,\SIC I'ISHI3RIES ISTESTIGATIOSS

150 140 130 120 1 IO I I I I I u 3.k I I I

600 M

I I I I I I I I 1 150 140 130 120 11(

FIGURE 5. Vertical profiles of temperature, salinity, oxygen and phosphate from the surface to 600 meters, August 1955.

(a) Temperature, degrees Centigrade. a small area and through a narrow range of depth thermocline. In spring the water receives more heat the temperatures may actually increase with depth from the sun and a thin layer of warmer water ap- at about 100 to 150 meters. pears at the surface. A new thermocline is formed Offshore the upper waters vary seasonally in a near the surface and this strengthens and becomes rather smooth and regular pattern (Fig. 6.). In Janu- d6eper as the summer passes, and the original winter ary and February a well-mixed surface laxer is found thermocline loses its identity. The surface is warmest with the water becoming colder quite suddenly be- from August to October but the new thermocline con- neath it. The regioc of sharp change is called the tinues to deepen until finally it reaches the depth of PROGRESS REPORT, 1 JULY 1956 TO 1 JANUARY 1938 3;

150 140 130 120 I 1 I I I I I

0< 34 00%. 34 007, - 34 20%. 34 2096. - 34 40%. 34 40%- 34 605h. 10 > 34 60%. --- MAJOR MINIMUM ..a .a* INTERMEDIATE WATER +++ SOUTHERN MAXIMUM

I I I I I I I I J 150" 1 405. 130" 1200 11

FIGURE 5-Continued

(b) Salinity, parts per mille. the original thermocline. A curious result of this se- talrrn from Robiiison, 1957, arid Mrs. Robinson also quence is that the high temperature5 are found later prepared the rest of the data for the figure.) in the year at deeper levels than at the surface. Heat Near the coast two entirely different causes of sea- is still conducted downward by the process of mixing soiial change are found, and these alter the simple long after the highest surface temperatures are past. offshore sequence. The first is upwelling, which occurs This circumstance niay be of soiiie importance in the earlier south of Point Coilwption than northward. To distribution of dissolved oxygen and will be mentioiled the south it occurs at about the time of the offshore again. (The tipper left-hand section of figure 6 is seasonal low in temperature. t'pwelling arid seasoiial 38 CALIFORSIA COOPERATIVE OCEASIC FISHERIES ISVBSTIGATIOSS

150 140 I30 120 11 I I I I I 1 I

, ... , [ C

--- MAJOR MINIMUM ..-...INTERMEDIATE WATER ...... e++ SOUTHZRN MAXIMUM

,OO M

I 1 I I I I 1 I 150 140 130 I20 I'

FIGURE 5-Continued

(c) Oxygen, milliliters per liter. cooliiig cornbind result in a wider raiige in tempera- The second priiicipally coastal cause is the seasonal ture than is fouiid oRshore. Sorth of I'oiiit C'oiicarptioii ebb and flow of the> c.ouiitercurreiit. This ciirrmt, ~ipwelliiigoc'curs later aiid leiigttitns the cold period. which is foiiiicl off Baja Califorilia iii the fall. briiigs Hiid diiiiiiiishea tbe sea.;oiial raiige n-(111 below that of n ariiier water froiii tlic. south i~~rtli~vestvart1 aloilg the offshore natcrs. Thiis the hlarvli aiitl ,Iugnst tem- the coast. Tt iiicrciiscs tlic fall high iii tciiipcratnre peraturcs of C'apcl Coliirltt ( :3O0 K) are 12" C ant1 ant1 citc.iitls it lo~gciioiigli to tlclay the spriiig low. 19" C whilc off ('apt> 1Ieiidociiio t1ic.J arr Iwtli b(>tucwl It \rill be swii to Irw (>\ ('11 iiiorc~ cxffrrtiw iii alttbring 10" c alld 11" c (lr'1ps. 4a and 41)). thc saliiiity. I'ROCRERS REPORT, 1 JUIAY1956 TO 1 JAN17ilRY l!K3 39

150 140 130 I 120 1 IO I 1 I I I I I

--- MAJOR MINIMUM ...... INTERMEDIATE WATER +++ SOUTHERN MAXIMUM

600 M' I

600 M

600 MI , I

I I I I I I 1 I I11 150 I40 130 120 110

FIGURE 5-Continued

(d) Phosphate-phosphorus, microgram atoms per liter.

The rrsults of the various seasonal forccs arc shov 11 is dwrcascd airtl tht. roc11 1)rriotl Iciigtlicncvl 111 111)- in figure 7 for the surface temperatures. ORshore the n elliiig. 13rtwcc.n l'oint ('oiiwptiou aiitl l'iiiita Eli- seasoiial variatioil is largely the result of radiation gciiia upwolling iiii.rc~asc.s the scasollal raIlg(1 South aiid exchange with the atmosplicrc,. A siinple pattcril of I'iiiita Eiigeiiia thc fall c.ouiitt.ri.iirreilt rd1v.s thc is foiuid n ith the ranges greatest iii the north, \\here raiige abor P that ofshorc airtl tltla~s t tic lo\\ uiitil the variation of simliglit is greatest Sear the con- latc spriiig (Data for thc arcas 40-43" IK 12'7-130" TT, tineiit Iiorth of Poilit Conreption tlic seasonal range and 13-50" S 124-127° TTT, arc fro111 RobiiIsolI, 1957 ) .P 0

50 Q b

100

125 40C-45”N 130 -135’W 25 MILES OFF POINT CONCEPTION

JAN FEE MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEE MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Om

100

125

185 MILES OFF POINT CONCEPTION 70 MILES OFF PUNTA ABREOJOS 26”N-114‘ W

FIGURE 6. Seasonal variation of temperature in the upper 125 meters at four locations. Temperature in degrees Centigrade, depth in meters. The upper left-hand section is from Robinson (1957); the other sections ore from CCOFI data, 1949-55. 41

12 16 20 24OC 60- 40-

12 16 20 24 60 -

12 16 20 24 60-

!$ ;;AlI , 0 12 16 20 24 30" 60-

25- 25- 25-

12 16 20 24

I I I I I 130" l2P I IO FIGURE 7. Seasonal variation of temperature at the surface off the 12 16 20 24 western coast of North America. Temperature in degrees Centigrade. 60- Values over five-degree squares are from Robinson (1957); values at 40- Blunt's Reef, North Farallon Island and Pacific Grove are from U. S. 2 Coast and Geodetic Survey (1956); values at numbered stations are 20- from CCOFI data, 1949-55. -

12 16 ' 20. 24 'l'hert> are marked year-to-year differences in 60- Inonthly average temperaturc.. Such diff'erences are 40- indicated in the long and continltous (40 years) data 4 20- for the Scripps Pier (Fig. 8). (Teiiiperatures at this position will later be shown to represent to a high 12 16 20 24 tlegrcv the general flnctnations in conditions off 60- southern California and northern Baja California.) 40- The maxininni observed range of average monthly temperature is about ioC and the average range is nearer j" (2. The frequency distributions are not 12 16 20 24 symmetricd, especially during the months of mini- 60- niiitn temperature ( February through April). In this period the mean temperatiire is closer to the minimum g;0"I1 I I, thaii to the maximllnl of the range. This can be in- 0 * terpreted to iiieaii that large temperature departures 12 16 20 24 in the cold months are caused by an intrusion of warm 60- rather than cold water. In late summer an opposite as! inmetry is less clearly snggested. $2, In regions of small seasonal range the highest teni- 0 peratures in 011~year may be lower than the lowest 12 16 . 20 24 FIGURE 8. Frequency dis- 60- tribution of monthly in ailother. Thus the monthly temperature averages average temperature at at Sorth Farallon Island (where the seasonal range is Scripps Pier, La Jalla, rednced by upn elling) in 1930 ere higher through- from 1917 to 1956. n Temperature in degrees ont the year than in any month in 1955 (Fig. 9). Centigrade. 12 16 LV L-r b 42 CA1,IFORSI.I COOL'ICRATITE OCILli\'IC FISHERIES JSTESTIGATIOSS shown to be small by the first profile, has now almost 16- "C entirely disappeared. Still farther south the amount of water of low salinity has diminished and the minimum has been 14- ,940 gradually eroded by vertical mixing. The California Current does not terminate here, however, but can be 12- traced to the west by its low salinity into the west- /-\, 1955 ward-flowing North Equatorial Current. The effect of the subsurface countercurrent is most 10 - rr +,a) strongly seen in the last profile. The water, as it en- ters, has the temperature-salinity relation character- 8- istic of the Equatorial Pacific water. The salinity is 111111111111 sufficiently greater than that of the California Cur- JAN DEC rent water above it and the clecper Pacific water below it to produce a maximum which continues as far north FIGURE 9. Monthly average temperature at North Farallon Island in 1940 and 1955. Temperature in degrees Centigrade. as Guadalupe Island. After the local maximum ha? been mixed away th(3 Equatorial Pacific water can Salinity still be identified in a state of transition along the coast possibly as far north as the Gulf of Alaska, and The California Current brings water of low salt in offshore waters as far as 40" N latitude. coiitcnt (about 32.5 parts per mille is the mininiani treain) from higher latitudes dowi The direct effect of the seasons upon salt coiit(~1itat mixes with water of higher salinity the siirfacc is limited to proce5Ses of prwipitation from below, from the west, from the inshore upwelling and evaporation. Jacobs (1951) has estiinateil thc areas and the south (Figs. 10a aiid 10b). At tiiiies difference brtwcen thcv terms in each season. Over (Fig. 10a) the Coliuiibia River makes an appreciable the northern part of the current, rainfall prrdonii- contribution of fresh watcr and at other times the nates thronghoiit the par, aid evaporation in the countercurrent in the south contributes vcry salty south, with the bonnclary at Sail Francisco iii summer \vatu (Fig. 10c). and at Poilit Coiicc3ptioii in winter. The wasoiial This history of the lowsalinity Subarctic water as change5 are not large coiiiparrd to other areas of the it moves_ down the coast is shonn by the vertical pro- oeran. Tlip largest tlifY(~rcwct~is fount1 oft' Washington files of figure jb. On the npp~rline the water of low aiid Oregon her(> rainfall exceeds evaporation in salinity is shown cwming in aboyc. 200 nirters. Already tlie winter by 1-1- cciitiiiietcw per inoiitli aiid in the the horizontal niixiiig (wliivli talies place faster in the simmer by only 3 cciitimeters per month. If this upper layer) has caused the snrfaw layer to be differc.nce of 11 cciitimetcm of rainfall wew mixed increased more than that below the perinanent ther- into the uppw 30 iiitJtc,rs of natrr of about 32.5 parts mocline, and a slight but clearly detectable aiid per iiiillc the salinity TI onld drop by 0.12 part per continnous minimum can be seen (it is iiidicated by inillc, aiitl this might b(x the order of the seasonal vari- the loiig dashes). Values greater than 34.00 parts per ation expectccl from exrhaiige T\ ith the atinosphere. mille (the shaded areas) are found over niost of tlir Such a inial1 imgc is cliffic~iiltto detect against a dceper waters of the North Pacific (Sverdrup et nl , backproiiiid of stronz v(Jrti(aill and horizontal varia- 1942) except where they are interrupted by Iiiteriiic- tion (Figs. 5b mid lOa-(l).The niiiiininiii vain(, ~~onltl diatc Tater (dotted line). This water is generally snp- fall at about tlie tinic. of year when the. ~111~1soff posed to form (?bid.) ill the western Pacific at tllp \Y\'ashington are from the southvmt, aiid thcsc ma.\- iiitersrction of the warm salty Kuroshio and cold, lo~v- bring in eiioiigli salty, offshoro uater to caiiccl or saliiiity Oyashio Currents iii the winter, alid it sinks revcme the trc.iid. 111 any caw, no such consistent to a depth correspoiiding to its density after iiiixin: ininiiiiiiiii has been found in the offshore \\i\tcrs of and \preads over nearly all the North l'arific. I11 the the California ('iirrciit. ,\lthonph several large upper profile it loses its identity in the 1ow-salinit)- changes arc' iiitlicatcd in the data taken by thc CCOFI Siibarctic water of the California Current, aid in the progrwin iii this region, they occqr in such ti sc.attc.ret1 other profiles its low value i5 gradually incrcJasetl by fashion as to prcwiit 110 coherciit pattorn at this inixiiig lvith the higher sa1iiiitic.s of the Equatorial n riting This niay iiicaii that offshore the seasonal I'acifir and transition water to the east. I tiriations are small cmnpared to changes of other licfor~the watclr rcachcs the latitude of Ran Frail- pcriods, and this will be taken up in the section on cisco much more east-west mixing has talien place, and long-ttmn variationh. the infiux of salty water from thr west has greatly Sear the coait, ho~vcvcr,several sorts of scJasonal iiitciisificd the difference bet~vcenthe surface valiies chaiige are found. Tn the far north tlie rnnoff from aiid the minimum. The ~ffectof the Columbia River, thr Coliiiiibia Itivcr has a seasonal variation, I\ ith the PROGRESS REPORT, 1 JULY 1956 TO 1 JANUARY 1958 43

Lll Lll _..-..

40' 40

1 15W 14V I30 I20 I 1V

3c 34

3v 30

2e 26

FIGURE 10. Salinity at 10 meters, in ports per mille. (a) August 1955. (b) March (composite). (c) January (average of three years). (d) June (average of three years). 44 ChI,IFORSI.\ CXY3PERhTIVE OCEANIC FISHERIES 1SYRSTIC:ATIOSS highest outflow in &lay and June and the lowest from and reduce the seasonal range. In the south the sea- November through February. The U. S. Geological sonal effects extend well offshore, but in the north Survey (1952) reported that in 1951 and 1952 the the range is small and the nature of the variation is rate of outflow ranged from 1800 to 7000 cubic meters not clear. per second. Although the greatest outflow is about a Oxygen thousaiidth part of the California Current (Sverdrup, Oxygen will dissolve in sea water up to a limit al., 1942), the fresh water is lighter and lies upon et (saturation value) which depends upon the tempera- the top of the ocean water until it loses its identity by ture and salinity. Over most of the California Current mixing. the oxygen above the thermocline is concentrated to It is in the salinity that the eft’ect of the river water about 100 percent saturation. Oxygen is produced by is most obvious. spreads over the surface the It of the photosynthetic activities of plants in the upper southward-moving current in a thin layer affecting level3 of the ocean to which light can penetrate, and noticeably only the upper 10 meters. In this thin sur- it is consumed by processes of respiration and decay. face layer the salinities may be reduced from the off- Since there are no new sources of oxygen at depth, shore value of 32.5 parts per mille to as low as 30 the deeper waters become depleted in oxygen. The con- parts per mille. This is at once noticeable as a local centration of oxygen has been used as an indicator of minimum in salinity (Fig. loa). the “age” of the water, that is, the length of time In temperature and oxygen measurements the ef- it has been away from any contact with the surface ; fects of the river water are much less obvious, since and it is partly because of its low oxygen values that the values in the river water are not so vastly differ- the deep Pacific water is thought to be older than ent from those of the ocean water. The amount of the deep Atlantic water and to have originated in the dilution which has taken place by the time the waters Atlantic (Sverdrup et al., 1942). have moved 100 miles offshore (in the above case 8 Most of the time the content of oxygen at the sur- percent of river water to 92 percent of ocean water), face is at or slightly above 100 percent of the satura- obscures any difference. The same situation appar- tion value. Less often it is slightly below saturation. ently holds true for the phosphate. Although the effect The saturation value of oxygen depends upon both of the river water stands out on the charts of salinity, temperature and salinity, but over the range of varia- the charts of temperature, oxygen, and phosphate do tion of these two quantities in the upper layers of the llot show any corresponding offshore peculiarities. California Current, the temperature effect is several The CCOFI program has not nieasured the salinity times larger than the effect of salinity. The saturation north of Cape Blanco in the period December through value of oxygen is higher at low temperatures; thus February. The salinity in the area well south of the the deep waters, which are colder than the surface river shows a drop in July, which would be consonant waters, could hold more oxygen, but they rarely do with a maximum outflow in May and June, and the since the supply at depth is limited to mixing from values are below oceanic from July through Sep- above or vertical movement. tember. Tn summer the upper waters entering froin the Southward the two great causes of seasonal varia- northwest are high in oxygen, containing greater than tion in salinity are upwelling and current. The values 7 milliliters per liter (Fig. 5c). In the southwest change as the upper waters are moved offshore by the they hold generally less than 5.5. A striking feature wind at Point Conception and the countercurrent ebbs of the upper-layer oxygen distribution is the shallow aiid ilows south of Punta Eugenia (Fig. 11). The subsurface maximum found over most of the area in salty southern water advances in the fall and retreats summer and fall. Below this maximum, and at a level in the spring. corresponding to the salinity minimum, the oxygen North of Point Conception where the range of tem- shows a sharp drop. The percentage of saturation perature from March to August is reduced by upwell- value, which has been at or above 100, drops as ing the range of salinity is increased (Figs. 10a and markedly. This may mean that the water above the lob). South of Point Conception the range is less. permanent thermocline has relatively free access to March and August are not the extreme months in the the atniospheric oxygen, but that the stability of the south. It is in January and June that the 10-meter water at the level of the salinity niiiiimum (which salinities show the greatest effects of the countercur- allows a thin layer to preserve its low salinity over so rent (Figs. 1Oc and 10d). many miles of motion) severely limits the transfer of There are striking differences in seasonal variation oxygen downward from the rich layers. at the surface over the whole area (Fig. 12). The In the deeper layers very low values are found off extreme effect of upwelling is seen north of Point southern Baja California aiid extending northward Conception and of the countercurrent south of Punta along the coast. Values at 200 meters off the tip of Eugenia, with their high and low values at different the peninsula are less than one-tenth as high as those periods. In the intermediate area these effects combine in the northwest (Fig. 13). This water of low oxygen JAN FEE MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

25 MILES OFF POINT CONCEPTION

IAN FFR MAR APR MAY JUN Jut AUG SEP OCT NOV DEC Om

FIGURE 11. Seasonal variation of salinity in the upper 125 meters at three locations. 50 Depth in meters, salinity in parts per mille. From CCOFI dato, 1949-55. 75

100

125 70 MILES OFF PUNTA ABREOJOS 26 N-114 W 46 CALIFORSIA COOPERATIYE OCEAKIC FISHERIES ISVESTIGATIOSS the cold months the water has more oxygen than in 0 120 110 the warm months. The average range of this variation is about one milliliter per liter, though it niay sorne- times be higher. Thus the surface oxygen values offshore from Point Conception are usually slightly over 6 milliliters per liter from March to May and slightly under 5.5 from August through November. The occurrence of the high values is delayed over a month off Puiita Eugenia, corresponding to the delayed minimum of temperature. The high and low values are about 6 and 5 milliliters per liter. The surface values are sometinies less than 100 percent saturation. In periods of intense upwelling the water of low oxygen content from below may arrive at the surface and remain below saturation (as its temperature increases) for several days before saturation is attained. The slight subsurface maximum (Fig. 5c) has been referred to as a summer and fall occurrence. Such a FIGURE 12. Seasonal variation of salinity at the surface off the western maximum is rarely found in the winter or spring. coast of North America. Salinity in parts per mille. Values at Blunt’s The sequence of formation of the maximum is gen- Reef and North Farallan Island are from U. S. Coast and Geodetic Survey (1954); all other values are from CCOFI data, 1949-55. erally as follows: In winter the oxygen values in the mixed layer are fairly constant with depth at about has been discussed with the salinity and seen to be 100 percent saturation or very slightly above. In water from far south gradually weakening in distinc- spring the surface values begin to fall. The oxygen tion as it moves northwest. It is of high salinity and content at 30 to 70 meters depth does not begin to high phosphate as well (Fig. 5d). It must have been fall until July or August; thus a maximum value is below the surface for a long period, for its oxygen has found around 50 meters from late spring until win- nearly been consumed in the decay of organic matter ter, nearly always slightly supersaturated. from the upper layer. A possible cause of the subsurface oxygen maximum is the subsurface production by phytoplankton. A more likely one might be the “eiitrapriient ’ ’ of oxygen by the water during the cold periods. If the values near the surface, which is in contact with the air, decrease more rapidly from their common winter niaxi- mum, then the subsurface water will for some period contain more oxygen. The lag of the deeper values be- hind the surface in the period of minimum and maximum temperature has been mentioned. This would cause the saturation limits of oxygen to decrease later at depth than at the surface. Redficld (1948), after examining the seasonal changes in the Gulf of Maine, concluded that over the whole year photosynthesis there has considerably less effect than changes of saturation value, but that at the period of minimum temperature (and small change) photosynthesis may dominate.

Phosphate Phosphate is important to life in the sea as one of I 150” 140“ 13W 120” I 10” the principal nutrients. The North Pacific contains higher phosphate concentrations than the Atlantic or FIGURE 13. Dissolved oxygen, in milliliters per liter, at 200 meters, August 1955. Indian Oceans. Its maximum values are well below the surface, usually just below the oxygen minimum, The seasonal variations of oxygen at the surface which places them at a depth of 1000 to 1200 meters occur generally in response to the seasonal change in (Wooster, 1953). Values greater than 1 microgram temperature (and thus saturation value) ; that is, in atom per liter are found in the Subarctic water at PROGRESS REPORT, 1 JITLY 1056 TO 1 JANUARY 1958 47 the surface north of 45" N latitude, increasing to than they have been in the Atlantic. Redfield (1948) values as great as 3 at a depth of 200 meters. At and Redfield, Smith, and Ketchum (1937) have dis- corresponding latitudes in the Central Atlantic Ocean cussed the seasonal variation of phosphate in the Gulf the surface values are less than 0.1 microgram atom of Maine; and htkins (1929-30) and Cooper (1933 per liter (Sverdrup et al., 1942). It has been shown, and 1938) have discussed the variation in phosphate in fact, that for certain organisms the phosphate is in the English Channel. In both regions a marked present in sufficient quantity for growth everywhere change occurred in the upper levels in summer owing in the North Pacific (Goldberg et al., 1951). This has to the consumption of the phosphate by the phyto- not been shown, however, for all organisms and for plankton. However, the lowest values near the Cali- other nutrients. The phosphate continues to be investi- fornia coast at any time of year are generally higher gated in the Pacific, not only because of its own pos- than the highest values ever attained in the two sibly critical value, but because it may be an indicator Atlantic areas mentioned. The same consumption of of other nutrients. phosphate in the California Current would cause a The high phosphate values of the Subarctic water proportionately smaller drop in phosphate. Further- at 147" W longitude drop off sharply to the south more, the periods of minimum phosphate found by (Fig. 5d). Below 35' N in that longitude they are less the authors mentioned above occur in summer as the than 0.5 microgram atom per liter in the mixed layer. result of heavy plant growth. This same period in The average value over the southwest part of the re- the California Current is one of great replenishment gion is about 0.3 microgram atom per liter. Phosphate of phosphate by upwelling. In a discussion of the is concentrated at depth (Fig. 5d) and its upward dif- seasonal variation of oxygen in the Gulf of Maine, fusion is found to be limited, as was the downward which has already been mentioned, Redfield (1948) diffusion of the oxygen, by the stable layer below the made use of a relation between the oxygen and phos- seasonable thermocline. In regions where there is a phate transformation in the biological processes of salinity minimum below the mixed layer, the first photosynthesis and respiration. He accounted in part marked increase of phosphate is almost invariably for the seasonal change in oxygen by the change in found at the minimum value of salinity. In the Cali- phosphate. Using this relation, and taking into ac- fornia Current system the mixed layer is shallower count the maximum effect of photosynthesis allowed near the land. Some photosynthesis may take place by the observed values of chlorophyll "a" in the beneath the mixed layer in the nearshore regions, and region south of Point Conception (Holmes, personal the nutrients used in the process can be more easily communication), an absolute maximum consumption replaced than those in the mixed layer by diffusion of phosphate of the order of 0.4 microgram atom per from below. liter per month might be attained. The actual value is Over the Northeastern Pacific the horizontal dis- likely to be much less than this, and the amount of tribution of phosphate at 100 meters depth and the Upwelling necessary to produce the observed tem- horizontal distribution of zooplankton are very much perature and salinity effects near the coast could alike (Figs. 14 to 16). The higher zooplankton vol- easily counterbalance this consumption. umes are found in the Subarctic waters where they lie On the other hand, the phosphate values have not near the surface in the California Current region, shown the effects of upwelling as clearly as have tem- and especially in the regions of upwelling. Farther perature and salinity. The measurement of phosphate offshore the high values of phosphate are found at has not been carried on as successfully by the pro- greater depths, where no photosynthesis can take gram as have the measurement of temperature, salin- place, and where replenishment of the surface waters ity, and oxygen; and the measurement has not been is very slow. so continuous nor covered so wide an area. Higher The close relation of phosphate to zooplankton is values near the surface are found at the appropriate somewhat baffling if, as has been suggested, the phos- times as the result of upwelling, but the appearances phate values in the Pacific are high enough every- are not so regular or simple as those of temperature where to promote normal growth. The relation holds and salinity. however not only in a rough fashion over lar,ee areas (Figs. 14a and 14b) but in a remarkable station-to- RELATION OF THE ENVIRONMENT station coherence (Figs. 15a-b and 16a-b). This indicates that the zooplankton growth takes place in the TO THE PLANTS AND ANIMALS areas of high phosphate near the coast, and that par- The previous discussion has shown that the Cali- cels of this water moving outward into the main fornia Current system contains a band of cool water stream contain both high phosphate and high zoo- reaching from high latitudes far down the coast of plankton volumes. North America. It brings in waters of relatively high The seasonal variations of phosphate are more difi- phosphate content (Fig. 14a), in sharp contrast to cult to understand in the California Current system the waters farther offshore. Along the coast this 45 CSLIFOHSIA COOPERATIIT OCEASIC FISHERIES ISVESTIGATIOSS

I60 Id0

I60 I40 50

30 30

30'

, 20 I60 I40 I20 20 I I 160' I40 I20

FIGURE 14. Distribution of phosphate-phosphorus and zooplankton volumes, August 1955. (a) Phosphate-phosphorus, microgram atoms per liter at 100 meters. (b) Zooplankton volumes, cubic centimeters per 1000 cubic meters.

30" -

lIIIIIIIII:l,,l 12P 120"

FIGURE 15. Distribution of phosphate-phosphorus and zooplankton volumes, April 1950. (a) Phosphate-phosphorus, microgram atoms per liter at 100 meters. (b) Zooplankton volumes, cubic centimeters per 1000 cubic meters.

130" 120'

.- I 11 11 I I I I4It I I I1 I I I! , 130" l2P

FIGURE 16. Distribution of phosphate-phosphorus and zooplankton volumes, July 1950. (a) Phosphate-phosphorus, microgram atoms per liter at 100 meters. (b) Zooplankton volumes, cubic centimeters per 1000 cubic meters. Iiiglier valur of phosphate is reinforced by the tip- th(x larger part of tlie California (‘nrrrnt system. \v(.11 illy of deeper waters whose nlitrient properties Soine species arc distribntccl in the very c~lil,ric.11, llavr iiot been exhausted. From the south at a depth waters of the northeast ; others liniited Iwrhap b- a of about 200 meters another current, also high in need for higher teniperaturtls, are foiiiicl to the south- pliosphate content, nioves northward. This water has west and may have an upper teniperatnre limitation hiit little dissolved oxygen left (Figs. 5c and 13). This farther west. indicates that the oxygen lias been depleted by The requirements of the organisms shown are not iwpiration and the decay, over a long period, of well enough understood for 11s to conclnde that tlie orgaiiic: inaterial. The product of this decay is nntri- proptrties illustrated at the boundaries are the eflt~.- rnt nintcvial, which is transported up the coast im- tiw ones. The euphausiids, in particiilar, are difficult niediately below the surface layer and becomes to iiiidrrstancl since they nnciergo a dinriial migra- available to the plants by mixing and upwelling. tion, and are deep in the daytime and near the sur- The result, then, is a narrow band of waters all face at night. As they mnst niovc back ant1 forth along the coast which are high in phosphate and pre- across a wide range of temperature in their migration, sumably other nutrients. One effect of the richness of it is difficult to think that some temperatiire at a these waters is seen in the high volumes of zooplank- particular depth should be the major limiting factor. ton along the coast, (Figs. 11 to 16). which are highest Work has been clone upon this (Koden, Pt al., 1953) in regions where the iipwelling and mixing are strong- and is being continued. The euphawiid distribiitionr (.st. These high volumes contrast sharply with those (Figs. 1Sa to d) are from work niade available by of the less abundant waters of the west and south- Dr. Etluard Brillton atid the salp (listribtition (Fig. \vest, aiid it is this great mass of living matter which 1Se) is from Dr. LPOD. Ecrner. ac.roiints for thc coastal fisheries. This living matter, however, is of vastly different kiiids, eavh with its own particular needs, so that NON-SEASONAL VARIATIONS IN THE within the region the species have quite different CALIFORNIA CURRENT SYSTEM SINCE 1916 sorts of distribntions. Most of the planktonic animals The dcpendence of specific organisms on certain prefer the irearsliore waters, bnt sonic have particular properties of the water masses has been assumed and neetls which Cause thein to live in greatest quantity to some extent measured. If conditions in the water offshore. are different in one year froin another, certain organ- Relations have been foiuid between the character of isms which thrive in the one year might not do well ivatcr niasses and currents off southern California and in the other. If long series of data iwrp available for the marine plants, diatoms (Sverdrup and Allen, both the organisms and the current, the dcpenclence 19:Vl). Of particular interest is the finding that the might be explored statistically. The length of time offshore waters contain few diatoms, whereas the this series wonld have to corer would depend upon the eddirs of inshore water may contain large numbers. simplicity of the relation and upon the nature of the They found that the “age” of the surface water was variations in condition and distribution. If the period an iniportant factor. Newly np~velled water is high since 1949 contained several high1:- unusual years, in nutrients, but after it lias been at the surface for which were different from each other, the dependence a lony time, as is the case with the offshore waters, could be much more easily established than if the its nutrients have been consumed. years were more nearly alike. The planktonic animals have little power to move In order to have some background against which throngh the water and are transported largely by the the period of the CCOFI program can be examined, currents. Different species and different stages of one certain previous data have been used. In the late species may live at different depths and have different ’80s and early ’40s the cruises of the California Fish limitations. Some must live near the surface and some and Game vessel Bliiefin and the Scripps Institntion avoiid light and some move up and down. Some thrive vessel E. 1V. Scripps made many measurements near at high temperature, some at low and some over a the Channel Islands area of southern California. The wide range of temperature. The charts showing the E. W. Scripps also made one long cruise in 1939 from distribntion of properties have shown that the prop- Cape Mendocino to Punta Eugenia and two cruises erties vary in different manners. It does not seem im- into the Gulf of California, in 1939 and 1940. possible that an organism may be limited on one side In addition to these data, surface temperatures had of its distribution by temperature and on another been measured by merchant vessels for many years, side by some other properties, such as nutrients. Cer- and various agencies have collected these and ar- tain interesting examples of the regions inhabited by ranged them by nionthly averages for 5-degree squares particular species are shown in figures 17a to e, on of latitude and longitude for each year. Principal which are drawn certain other properties, which seem ainoiig these agencies is tlie Kobe Imperial Marine to coincide with their boundaries. The examples cover Observatory in Japan to which we are indebted for 50 CAJJFORSIA COOPERdTIT'E OCEASIC FISHI~~RIESISVESTIGATIONS

50" 0-199 0-50 200 2000 > 50 > 2000 -200 M TEMPERATURE [ C) -100 M TEMPERATURE (C)

3w 1...... \ .. .\; .':y{ ......

C d

- 200 M TEMPERATURE [ C) - 150 M TEMPERATURE ( C) --- 150 M 02 I ... \. ..

FIGURE 17. Distribution of certain zooplankton and certain tempera, 100-10,000 ture and oxygen values, August 1955. (a) Euphousia pacifica and > 10,000 temperature (in degrees Centigrade) at 100 meters. (b) Fuphausia gibboides and temperature (in degrees Centigrade) at 200 meters. M TEMPERATURE ( C) (c) Nematosceffis offontica and temperature (in degrees Centigrade) and oxygen (in milliliters per liter) at 200 meters. Shaded portion rep- lo" resents areo of occurrence of organism. (d) Styfocheiron carinatum and temperature (in degrees Centigrade) and oxygen (in milliliters per liter) at 150 meters. Shaded portion represents area of occurrence .... of organism. (e) Dofiofefto gegenbouri and temperature (in degrees Centigrade) at 100 meters.

...... i...... the pitblicatioii of such data over the North Pacific ture, salinity, and mind at varioiis places. With the Ocean from 1!)11 through 19338. In addition, for many exception of the surface temperatures from merchant years, the Ti. 8. Coast aiid Geodctic Surrey has taken vessels, howevcr, the hydrographic data are almost en- sea level temperatiire aiicl salinity nieasiireiiieiits at tirely from the Bluefin aiid E. 'IV. Scripps cruises 20 rarious of its tide gauge iiistallatioiis aloiig the west years ago aiid the CCOFI cruises which began in 1949. coast of North Aiiierica and Alaska. Observatioiis of These data woulcl seem rathpr scanty for an analysis surface temperature arid saliiiity from 7 923 through of variations in a major current over a long period, 1940 are available for the Bluiit's Reef light vessel but certain of the initial results have been encourag- aiid from North Faralloii Island. Surface temperature ing. The variations in temperature at points along the aiid saliiiity measttrerneiits have becii made daily at Pacific Grove and at Scripps Pier for riiaiiy years. coast of North Aiiierica show coiisiderable coherence Meteorological data are available from the U. S. over great distances. The major aiioiiialies in tempera- Weather Bureau in the form of sea level atmospheric ture, high or low, seem to last several months, im- pressure averaged by moiiths froiii 1899 to the present. plying that nioiithly averages are not ail unlikely With these data in hand, it has bcen possible to method of approach. Certain of thrse data are showii compare the variations froin year to year of tempera- by monthly anomalies (Fig. 18) ; that is, the value

FIGURE 18. Monthly differences from average sea surface temperatures (degrees Centigrade) at (1) 30"-35" N, 115"-120" W, (2) Scripps Pier, and (3) 25"-30" N, 110"-115" W; and (4) monthly differences from average northerly wind component (in meters per second) at 30" N, 110"-130" W. plotted iii dune of a gi\ eii year rtipresciits the aiiioiiiit 11 ca~is~for this bchavior has bwii songht iii the by which the arerage temperature in June of th;it variatioiis of the strength of the wiii(1. The Jiorthei.1)- year was highcr or 1on.c.r thaii the average of all the cwiiipoiicliit of wiiid (cwiiipiitetl from atniospherica FJmitlsfroin 1920 to thv prcsciit. (Honie of the data ;ire prcwrirc' tlifYci.eiicc1 at 30" N Iatitudc bct\\(vii 110" \Ir froiii the J;ipancse soiircw and are availablo oiily aiid 1:lO" \V loiigitritlr) was gciierally stroiigvr iii tlic throng h 1!)38.) last tl('(aiitl(' (Fig. 20). 12 sigiiificaiit corrc~latioiihas Tliv priiivipal cold pcriotls I\ ('IT from ]!I20 to 1924, b(wi foriiitl bvtu wii tlic \\ iiitl ;iiioiiialies ant1 tlicl teiii- iii l!XE aiid l!):K3, and froiii 1948 through 19%. Thc pratiirc aiitl wliiiity aiioiiialic.s iii tlie spriiig aiicl \\ ariiiclst groiips of J (wrs 11 (w froiii 1 !E6 throiigh wi.1.1- siiiiiiiier iiioiiths n here as iiitiiiy as 18 J (wrs of 1931, aiid froiii 1!1:11 thiviigh 1944. The varintioii in (lata tirr >i\.iiilabl(b (Rode11aiitl Reid, &I\. iii pr~parti- the sti*c,iigthof tlir iiorth niiitl froiii its nioiitlily iiieaii tioii 1. It is iii thew iiioiit lis thiit the. greatest variations ovw the 5aiiie pciriotl is also slio~rii(li'ig. 18, part 4) froiii thc iii(mi ;ire foiiiitl in tlic xi iiicl data. Iii Augiist, aiitl a wrtaiii siiiiilaritJ- in loiig-tc.riii variation is se('ii altlioiigh tlic \rinds arc stroiip, the variation of bet\\ ccii I\ iiitl aiid tcwporatiirc~aiioiiialics. iiiontlily avc'ragc+ abont the loiig-tcrni iiicaii is nincli Thr last ~PJYyears stand out froiii tlie loiig-term smaller The iiiechaiiisiii of this relation niay be ail mea11 both iii tcIiip(~ri\tiir(~aiid salinitj- (Figs. 19 and iiicreascd aiiiomit of iip~elliiig, aiicl I 20). Tlic JZ iiiter and spriiig tenipcratiires are low aiid creasc~l aiiiowit of StIbiir(>ti(>watw the siiiiiiii('r riil1le\ iiiorc iloriiial or high. The saliiiity sont h by thcl iiortherly wiiids. The corrrlatioii holds values arc. high iii \\ iiiter aiid spriiig aid iiiore iiearly in all the data from 1Slnnt 's Rccf to Nag?daleiia Ea)- iioriiial the, rest of the year. 12lthongh tlicrc is some diiriiig thew months. In thcl latter part of tlic year variatioii from J (Jar to J ear siiiw 1!)1!),thc deviations the I\ iiids have 1 arid less, aiid iio sigiiificaiit correla- have not bceii cxtreiiie (Fig. 18) cxwpt possibly south tion lias hccii foiiiid. of l'uiita Eugenia. Froiii 1949 through 1956 thcre The fact that temperatiire lias been lon (wtl and nc~e110 years as extrcinc as 1!126, 1931, l9Y3, or 1941 salinity raised diiriiig this period implies that at least PACIFIC GROVE SCRIPPS PIER 'C 21r

I,,,,,,,,,,, J FMAM J J ASOND

- 1920-48 -1949 -56 111111111111 JFMAMJJASOND

,401

J1,,,,,,,,,,, FMAMJ J ASOND

FIGURE 19. Average surface temperature (degrees centigrade) and salinity (parts per mille) at Pacific Grove and Scripps Pier far the periods 1949-56 and 1920.48.

111111111111 JFMAMJJASOND part of this process is iipwelliiig, siiice the evaporation iiiiiiiis prrcipitatioii values here (dacobs, l!)jl) are qiiitc siiiall. There are no earlier phosphate (lata mitli liich the C'COFI data can be compared. *C It may tlieii be concluded that the period from I949 to 1956 is distinguished from the previous 15 or 20 ycars by substantially colder waters in the first few iiioiiths of the > ear. There are cliffereiices ill the years froiii 1!)4!1 to the prrsriit (which will br talwii np latcr), but they have nearly all exhibited this colder featnrr in the early moiiths. The sea snrface temperature in the period from 1945 to 1936 showetl no values extreme c.iiough to coiiipare 11 itli those of the iiitriisity and enduraiice of 1926, 1931, 1933, 1940, or 1941 (Fig. 18). A certain coherelice of tlie systeiii is at once obvions from the (lata from 1959 to the prcseiit (Fig. 21). These data allow one to generalize somewhat about thr diffrrcxce iii tlir varions years. South of I'uiita Eugenia the data in the 5-degree square show some greater irregii- JFMAMJJASOND laritie\ aiid iiiclicate soiiie differelice in behavior froiii iiortli. show wile FIGURE 20. Average northerly wind component and temperature in those to the ThcJ,v generally tlir recent period compared to averages for 1920-38. (a) Northerly wind plic~ioiiiciioiiof cold springs w1iic.h have a sigiiificaiit component in meters per second at 30" N in years 1949-56. (b) Tem- correlation with tlie ~iortherlywiiids. The iiiost re- perature in degrees Centigrade at 30"-35"N, 115"-120"W, 1949-56. (c) Temperature in degrees Centigrade at 25"-30" N, 110"-115" W, iiiarlmble \.ai-iatioiis iii this period have been south of 1950.56. No data 1939-48. I’iiiita Eiigriiia where. tlir late fall of 1931 was iiiiii\ii- iioriiial in wiiitw and spring aiid nns soiiic~~vliataboyc ally 11 iiriii aiid tlic siiiiiiii(1r of 1!)33 \I as iiiinsiiallj- iioriiial iii the rarly fall. Iikc~~vis~~I!)>() its below cwltl. It is iuifortiiiiate that iii 1!)40 aiicl 1!)41, wli(w iioriiial iii wi1itc.r aiitl spriiig biit (lit1 iiot show tlic thteiiipct.atiirc+ over all tlir west roast iiortli of Sail satiie siiiiiiner and fall wtiriiiiiig as Iiad 19-k!). Tliv Diepo are kiiowii to Iiav~btwi at thcir highest iii the ycar 19.51 was IIIO~P iioriii;tl diiriiig thc first fcw last 2,; j cars, no data are available from tlir vicinity iiiouths biit at diflereiit placcs sliowd both wiriiiiiig of I’iiiita Eugeiiia. A wiiipai.iwii of 1951 with 1!)40 aiicl cooliiig ton-ard the eiid of the ycar. TII iiiost and 1!)11 might bc of iiitcrcst places, 1952 hcg:a11 solllc~\\Ilat above Ilorlllwl but Owr most of the area, 1954 vas the warniest year, droppc‘d below iioriiial iii thc fall. Tlici yvar l!)Xi thongh thew was at least one cold month ton arc1 the begiiii slightly above normal and iii the. iioi-tli \viis eiid of the year. The year 1919 began w-cll below above iiorriial agaiii in the fall but iii tlic soiitli vas

1951 1 1952 1953 1954 1955 1956 I1957 t2 I I I I

-2

-4

FIGURE 21. Temperature anomalies, 1949 to 1957, ot four locations as referred to 1949-56 mean. Temperature in degrees Centigrode cooler iii the fall. The year 1954, iii most of the data, ucrc uwtl before 1940, it is not ray,- to compare T\ as ~~11abow normal most of th(. year dropping be- present popiilatioiis with those in the past, yct soiiie Ion only iii Kovciiibw and Dccruibrr iii most places. sigiiificiiiit iiitlicatioiis have been obtaiiied. The nature Tlie y1ar 19S, iii much of the data, was well below of the .watcsrs of the California Furrelit has been tlie iioriiial and 19.56 was likewise g!ciicmilIy cool. Tn discusscd, aiid thc tlistributioii of tht. prolwrties, vspe- l!),;i, tlic. sontherii California waters seeill to be at or cially pliospliatc as an intlrx to the iiutririits, has abovr iioriiial through ,Jiiiie (Fig. 22). Xorth Faralloii bwn describctl. ,2 siiiiplr relatioii betwen zooplaiik- Islaiitl shows tetiiperatnres slightly below normal av- ton aiid phosphate has bwii shov ii (Figs. 14-16). crag~lthrough eJii~io,aiid data from Blmit ’s Reef I’liospliate has iiot becii measnred regiilarly, aiitl 1 cJry throiigh April sho~v:illi(>s genc.rully b(>low ~i~r~~iitl.few 1iiCilsiirClil(~iitSin this rcgioii \v(’rc iiiacle before 1949 ; thrrrforc. in using the available data any sig- iiific.ant re1;itioii of zooplaiiktoii to the eiiviroiimeiit OF VARIATION IN POSSIBLE EFFECTS THE nliich caii iicco111it for chang(l5 iii time of the 11opula- CURRENT SYSTEM UPON THE ORGANISMS tioii iiiiist iiivolve soiiie othrr parameter than phos- 1kfoi-c 1949 only ii fen iiirw,iireiiiriits of thc plant phate 01- nntriciits-sonic. yai*ametcr for hicli data and aiiitiial popiilatioiis of the California Ciirrcwt (>xist ov~ra longer period. systeiii had been niade. Siiicr 1!H9 the voluiiic of Til previous discussion of tlic ciirreiit systciii aiid zooplaiiktoii lias bceii iiirasurcd o\ er a grrat part of it5 variation it was iiieiitioii(1d that the only property tho ciitwiit iirarly (~rrymonth, and iiiiic*li has beell for nhich aiiy loiig series of (lata exist is trnipcrature. lcariirtl about the. distribiitioii iii spacr sild time. Be- Thc geiicral relatioil of tenip(>raturtJto pliospliatc has cause diffcreiit iiietliods of measnriiig zooplankton iiot yct been nicwtioiied, but an esaniiiiatioii of the BLUNT'S REEF - 1923-41 MEAN - of the surface waters of the California Current and 14-OC - the iiicrease in their inshore salinities are due to an - internal redistribution of thc heat and salt, as wonlcl - resnlt from upwelling, rather than a loss of heat and z...... z...... *.'.. *...... sa..- re- ...+ ...... < .. '.=' water to the atmosphere, then thc accompanying ... distribution of phosphate and other nutrients would 8; 1.1 I I I I I I I I I I- have considerably eiiriched the surface waters. JFMAMJ JASDND

FARALLON ISLAND - 1925-42 MEAN - - 16-OC 1000 STATIONS AVERAGED 14 - - 9: 1950 9 - -;800 f .... 0 - 0

I - 600 *i- I I I I I I I I I I I I- $1953 JFMAMJ JASOND :2 > I I z 1956 400 HOPKINS MARINE STATION - 1920-55 MEAN -- z 16-"C t.. ... 4 0 I 1952 1955 w 200 4c I

+I951 . 1949 - 10,l,,lIll,lIll 0 JFMAMJJASOND 10 M TEMPERATURE ( C) SCRIPPS PIER - 1917-55 MEAN - FIGURE 23. Temperature at 10 meters (in degrees Centigrade) and 22-OC - zooplankton volumes (in cubic centimeters per 1000 cubic meters) averaged from February through August for each year from 1949 through 1956.

18- The dependence of zooplankton upoii the nutrients 16- is, of course, an indirect one via the phytoplankton. - If it had been consistently measured, the phytoplank- 14 - ton might be expected to yield a better correlation than zooplankton with the nutrients. In the region betn-een Point Conception and I'unta Eugenia, how- 1956 ...... ever, a satisfactory relation has been found during 1957 - the sew1 ymrs for which data are available (Fig. FIGURE 22. Temperatures in 1956 and 1957 at four locations as com- 23). (Zooplankton data were prepared for figure 23 pared to long-term means. Temperature in degrees Centigrade. by Jlr. James Thrailkill of the U. S. Fish and Wild- charts of temperature and phosphate shows that over life Service.) Indeed, if there is no direct relation a vast area, inclncling the riearsliore waters of Baja between zooplankton growth and temperature, the California and the west coast of the United States, relation shon-n between the temperature as an in- high phosphate values are generally accompanied by direct nieasiire of nutrients and zooplankton as ai1 low teniperatures. This holds not only vertically, indirect measure of phytoplankton is better than where the deeper waters contain the products of de- woulcl be expected, and greater irregularities will cayed organic matter, but horizontally as well. The almost certainly be found in subsequent data. Subarctic waters of the north, which form a great ITithiii certain limits of temperature, the zooplank- part of the surface waters of the California Current ton volumes were lowest when the temperatures were system, are both cool aid high in phosphate. There- high and highest when the temperatures were low fore, in the regions of the California Current one may (Fig. 23). Data from 1940 and 1941 cannot be plotted with some confideiice use the low temperature in the on this chart, since the cruises made in those years mixed layer as an indicator of higher nutrient prop- covered only a small part of the area. However, there erties. is qualitative agreement in that the plankton volumes The succession of relatively cool years from 1946 measured in the region of southern California in has been mentioned. Where data hare been available 1941 (E. 11. hhlstrorn, personal communication) salinities hare been found to be higher near the coast averaged only 103 cubic centimeters per 1000 cubic in the same period. If oiie assumes that the cooling meters, and 1941, as has been shown (Fig. 2l), had I’ROGRESS REI’ORT, 1 JTTAP 1956 TO 1 JANI‘ARY 1958 55 also the highest temperatures observed in any year unfortunate that we do not have a coverage .of the from 1931 to the present. area in years when the catch was high or when at South of Punta Eugenia, where the zooplankton least there was a high survival rate. Until such a volumes have generally been smaller and the tempera- year occurs any correlations of this sort will be tures higher, a similar plot of zooplankton volumes severely limited. against temperature is not nearly so regular. Al- though a similar trend can be seen, these data are hardly convincing. REFERENCES Correlations of this type are difficult to make not Atlrins, 11‘. R. G. only because the temperatures and zooplankton are 1923. The silica content of some natural waters and of cul- ture media. J. Mar. BioL .Insn. 7’. IC., rol. 13, PI). not sampled as coinpletely as we should desire, but 151-1 .5!>. because the zooplankton varies from year to year in a 1026. Seasonal changes in the silica content of natur:il fashion more complex than gross amount. There are waters in relation to the phytoglankton. J. Mar. Biol. data to suggest, at least, that the response of the rlssa. r. K., rol. 14, pp. 89-99. zooplankton to changing hydrographic conditions is 1928. Seasonal variations in the phosphate and silicate content of sea-water during 1926 and 1927 in relation to not only in mass but in change of species as well. the phytoplankton crop. J. Mar. nio!. Assa. U. IC., Salps, for example, map predominate one year and vol. 15, pp. 191-205. other groups in other years, with the volumes not 1930. Seasonal 7 ariation in the phosphate and silicate con- changing significantly. All of the area is inhabited tent of sea-water in relation to the phytoplankton crop. Part V. Novemher 1927 to April 1920, coinpnretl (Bigs. 17a-e), aiid it can well be imagined that a with earlier years from 1923. d. Mar. BioZ. Assn. U. change in conditions could cause the boundaries to Ii., vol. 14, pp. 821-862. move so that the species would inhabit slightly dif- Berner, Leo D., Jr. ferent regions, without a great change occurring in 1957. Studies on the Thaliacea of the temperate northeast gross amount. Pacific Ocean. Unpuhlished doctoral dissertation on file in the Lihrarg, l’niversitg of California, Scripps Institution of Oceanography. 144 pp., 26 figs. CONCLUSION Boden, Brian P., RIartin W. Johnson, and Edward nrinton The waters of the California Current and their 1955. The Ihphansiacea (Crustacea) of the north Pncifir. 7Tniv. Calif., Scripps Inst. Oce., Bull., vol. 6, pp. 287- manner of flow in the fishery region of California, 400, t55 figs. both horizontal and vertical, have been briefly de- scribed. The seasonal variations and long-term varia- Canadian aoint Committee on Oceanography 1956. Physical, c11emic:il nnd p1;mliton data record. Project tions have been mentioned, and some attempt at NORPAC, July 26 to Septemher 1, 1955. Prepared by relating the environment to the organisms has been Pacific Oceanographic Group, Nanairno, l3. C., Dupli- made. The bearing of these matters upon the central cated report. File S 6-17-4(2).202 pp., 4 figs. problem of the CCOFI program, that is, the fluctua- Cooper, L. €I. N. tions in the catch of the sardine and other oceanic 1933. Chemical con\titnents of hio1ogic:rl importance in the fishes, has not yet been mentioned. One difference Ihglish Chnniiel. Part I. Phospate, silicate, nitrate, between the last decade and the previous period when ammonia. Part 11. Hjdrogen ion concentration, excess the sardine fishery was at its height has been pointed hase, cnrhon tliositle, and oxygen. J. Jlar. Biol. Assti. U. IC., 101. 18, pi). 677-7.53. out. The temperatures during the early months of 1938. I’hosphate in tlie English Ch:innel, 1993-8, with a con- the year-the sardine spawning months-have been parison with earlier 3 rnrs, 1916 and 1!)23-:12. J. Ilnr. consistently lower in the last ten years and with BioZ. Assn. U. IC., vol. 23, pp. 181-195. certain assumptions inferences bearing upon the sardine problem can be drawn. These cooler months Cromwell, Townsend, and .Joseph 1,. Reid, Jr. 1956. A study of oceanic fronts. Tellus, vol. 8, no. 1, pp. seem to be cooler because the winds were stronger and 94-101. caused more upwelling. Assuming this relation to hold, and that the low temperatures are indicative Goltlherg, Edward I)., Thrwtlore J. TT‘;tllter, and Alice Whisenand of high nutrients, then tlie result of the enrichment 1951. Phosphxte utilization hy diatoms. RioZ. BulZ., vol. 101, no. 3, pi). 274-284. has been higher zooplankton volumes. If this relation between temperature and zoopl&kton is a real one Imperial Marine Observatory, Kobe, .Jal)aii and has held over the last 20 years, as it did in 1941 102.5. The mean atmospheric pressure, cloudiness and sea surface temperature of the north Pacific Ocean and the and from 1949 through 1956, then we must assume neighboring se:~for the lustrum, 1910 to 1020. Kobe, that plankton volumes were smaller in the great Imp. Alar. 01)s.. 681 pi). period of the sardine fishery than they are now when the sardine catch is much reduced. How the zooplank- 1927. Thr mean ntmosplicric pressure, cloudiness and sea surface temperature of the north Pacific Ocean ant1 the ton aiid sardines could be so inversely related is neighboring seas for the gear, 1926. Kolw, Imp. Alar. beyond the purpose of this report to speculate. It is Ohs., 171 pp., 20 figs. Sttiff. Sollth I’acific I*‘ishc.ry 1nvvstig:itions 1952. Zoo1ll:tiikton v~luni~off the 1’:tcific Coast, 1941. 7’. A”. I.’islr crnd ll.i/r//. ~’cvv.,h’lwr~. Sei. Repf.: Fish.. no. 73. 3i lbp. 1!)3:3. fbid. I!)>? ; JIO. 100, 41 1)p. 1!G&a. Ibiti. 1!)4!)-30 ; 110. 1”. :4 1)P.

1!).7411, Ibid. 1!)5:3 : 110. 132, :

(ins.) 13iologic:iI restilts of tile portion of NORI’AC OCCII- pied Iiy ngeneii,s 1i:irticip:iting in the California c‘o- o1ierative Occwnic 1~’isheric~sInvrstigntions. Srertlrnp, 11. 17.. :1ntl E. w.Aillrll I%

~~Rossliy, C. G. Wooster, n’;irren Scrirer 1!)3G. Dynamics of steady ocean current? in the light of ex- 1053. l’hosphate in the ea~~