CERATIUM IN THE PACIFIC AND NORTH ATLANTIC OCEANS 



waters are deflected to the south by the continent of 

 North America, along the west coast of which they flow 

 as the California Current. By the time this water has 

 reached a latitude of 30° north it has attained tropical 

 temperatures (above 20° C) and has become depleted of 

 nutrient salts. It continues into the North Equatorial 

 Current to complete the circuit. The polar front or 

 subpolar convergence of the North Pacific extends north- 

 eastward from Japan at a point at about 38° north lati- 

 tude. At this line the cold arctic waters of the Oyashio 

 meet the warm waters of the Kuroshio. Not only does 

 the North Pacific Intermediate Current originate here, 

 but there is considerable mixing of the two types of wa- 

 ter at the surface, so that from here the water of the 

 Kuroshio or the North Pacific West Wind Drift is colder 

 and richer in nutrients because of the admixture of cold 

 and rich water from the north. All the Carnegie stations 

 off Japan were to the south or east of the line of conver- 

 gence as indicated by Schott (1935), but in the hydro- 

 graphic studies of the Carnegie (see Sverdrup, 1944) 

 there was found in the upper 500 meters a definite line 

 of demarcation between the cold water to the north and 

 the warm water to the south, principally at the latitude 

 of 38° north, between stations 115 and 116. 



A loop of Carnegie stations, with a center about 

 northeast of Hawaii, lies inside the main current system 

 of the North Pacific, and extends into the subtropical 

 convergence. This central part of the North Pacific can 

 be likened to the Sargasso Sea of the Pacific. The water 

 is of high temperature and low nutrient content to com- 

 paratively great depths. For instance, the temperature 

 is often above 20° C to more than 100-meters depth with 

 total depletion of phosphate. 



South Pacific Ocean. --In the South Pacific also, the 

 current system is in the form of an extensive vortex; in 

 this case, however, it rotates in a counterclockwise di- 

 rection since it is in the Southern Hemisphere. In the 

 south of this circuit there is the South West Wind Drift 

 which travels easterly around the earth in a more or 

 less uninterrupted manner in the subantarctic latitudes. 

 This current is cold and rich in nutrients. It lies a little 

 to the south of the most southerly Carnegie station, sta- 

 tion 60, at 40° south. An offshoot of this great oceanic 

 stream, the Humboldt Current, extends northward up the 

 west coast of South America and brings cold, rich water 

 into this area. The waters from this region turn to the 

 left and flow westward as the South Equatorial Current. 

 The main part of this current lies at about 3° north lati- 

 tude. The water of this current increases in tempera- 

 ture and decreases in nutrient content as it progresses, 

 so that in the western Pacific it is very warm and poor 

 in nutrients, whereas in the eastern part, near its ori- 

 gin, it is not so warm (temperatures of 20° or less 

 around the Galapagos) and is richer in nutrients (25 to 

 50 mg P04/m3). It should be noted, however, that the 

 waters of the South Pacific are nowhere depleted of 

 phosphate although the surface temperatures may be 

 several degrees higher than in depleted areas of the 

 North Pacific. The South Equatorial Current gives off 

 numerous, If not continuous, offshoots to the south. One 

 of these offshoots departs at about longitude 120° west, 

 and thus forms a minor vortex with the Humboldt Cucr- 

 rent which has been called the Easter Island Eddy by 

 some. The water in this eddy showed the lowest phos- 

 phate content of any water investigated by the Carnegie 

 in the South Pacific. The currents of the southwestern 

 Pacific will not be discussed as no Carnegie stations 



were occupied in that area. The Equatorial Countercur- 

 rent is a narrow, shallow stream extending eastward in 

 a direction opposite to its neighbors, at about latitude 6° 

 north. It is warm and poor in nutrients to the west, but 

 has lower temperatures and higher nutrient content to 

 the east, probably because of admixture with water from 

 the southern current system. 



There are also Carnegie stations in the Panamic 

 area. The water in this region probably has a multiple 

 origin, a has both a high temperature and a high nutri- 

 ent content. 



Temperature 



In the North Atlantic south of the subpolar conver- 

 gence, the surface temperatures are mostly above 20° C 

 (chart 50). There is an increase in temperature south- 

 westward to maxima above 28° in the Caribbean region. 

 In the North Atlantic West Wind Drift the temperatures 

 rapidly decrease to 11° and 12° at Europe. At the other 

 stations, farther north, the surface temperatures are 

 mostly around 10° C. 



In the North Pacific there are six stations in water 

 with surface temperatures less than 10° (stations 119 to 

 124) south of the Aleutian Islands to the Kurils. Toward 

 Japan there is a rapid increase in temperature south- 

 ward so that there are only three stations in the transi- 

 tion zone between the cold northern water and the warm 

 tropical water of the south, fii the eastern Pacific, on 

 the other hand, this transition is very gradual so there 

 are seven widely spaced stations between the 10° water 

 south of the Aleutians and the 20° water of the tropics, 

 stations 125 to 131. 



to the tropical regions of the Pacific the surface 

 temperatures are mostly between 22° and 28° with the 

 highest temperatures in the west. Temperatures of less 

 than 20°, however, were recorded at two stations in the 

 region of the Galapagos, stations 42 and 43. The effects 

 of the Himiboldt Stream are noted in a general lowering 

 of the temperatures in the southeastern Pacific region, 

 although temperatures as high as 25.°27 were recorded 

 off Peru. The Carnegie stations south of 20° south lati- 

 tude were so far from South America that they do not 

 show the severe effects of this current. Only three of 

 the stations showed temperatures less than 20°. Farther 

 south, however, beyond 30° south, the effects of the South 

 West Wind Drift are very noticeable, with a fairly rapid 

 reduction of the surface temperatures to 14.°97 at 40° 

 south at station 60. 



Salinity 



The central North Atlantic in the Sargasso Sea re- 

 gion has the highest surface salinities of any area trav- 

 ersed by the Carnegie, namely over 37 per mille (chart 

 51). In the North Equatorial Current the salinity is 

 about 36 per mille; at the cold northern stations it is 

 mostly around 35 per mille, although there was one sta- 

 tion southeast of Newfoundland where the salinity was as 

 low as 32.66 per mille. 



In the central North Pacific the surface salinities 

 are slightly more than 35 per mille. At the subpolar 

 convergence this is reduced to less than 33 per mille 

 and the salinities of the North Pacific West Wind Drift 

 remain under this value to northern California. In the 

 Panamic region the salinity is quite low, namely, 30 per 

 mille. The values increase westward from this area in 



