132 U.S. NATIONAL MUSEUM BULLETIN 291 



0° to 1.5° C in depths less than 2000 m within a few degrees of 

 longitude. 



In surface waters the temperature remains below 1° C as far as 72° 

 W. Between 72°W and 75°W there is a rapid increase in surface 

 temperature to 4° C that marks the location of the Antarctic Conver- 

 gence as it passes north of 60°S just before entering the Drake Passage. 

 The 1.5° isotherm descends from the surface at 74°W to about 500 m, 

 then it rises somewhat and extends eastward at 200 m to 52°W. The 0.5° 

 and 1.0° isotherms descend below 3000 m between 50°W and 60°W. 

 The 1.5° isotherm ascends very gradually west of 79°W but remains 

 below 2000 m until 125 °W where it begins a steep ascent toward the 

 surface; at 143°W the 1.5° isotherm is located in 350^00 m, but it 

 swings sharply to the east under a layer of cold surface water and 

 does not reach the surface until 127°W. The 2.0° isotherm nearly paral- 

 lels the 1.5° isotherm 400-700 m above it. The upper waters (500- 

 700 m) between 75°W and 125°W are characterized by four cores that 

 represent northward tongues of cold water or southward tongues of 

 warm water that meander across the 60 °S latitude. The largest tongue 

 lies between 75° and 92°W where the 2.5° isotherm dips briefly to 

 1300 m. The Antarctic Convergence is again seen between 125° and 

 128° W where it passes southward across 60° S latitude after flowing 

 off the Pacific-Antarctic Eidge to the west. A wedge of very cold water 

 extends northward west of the convergence. The narrowest part of this 

 cold water lies between 142° and 150°W at 300-500 m where the warm- 

 est water is located between the 1° isotherms that lie at 200 m and be- 

 tween 700-1000 m. The peak of cold water spreads out with depth so 

 that temperatures less than 1° C are found at 2500 m between 128° and 

 160°W; the 0.5° isotherm rises to a peak at 1750 m at 145°W. This 

 mass of cold water has its origin in the Eoss Sea, and it serves as a cold 

 wedge that slices across the Circumpolar Water Mass. Warmer water 

 (1.5°-2° C) is encountered again to the west of 150° W. 



The distribution of salinity along 60°S also demonstrates the merid- 

 ional displacement of water (fig. 38). Low salinity water of less than 

 34.70%o from the Weddell Sea occupies the entire portion of the section 

 between 20° and 50°W. The 34.70%o isohaline rises vertically from 3000 

 m to 700 m at 51 °W; westward it descends to 2150 m beneath the con- 

 vergence zone at 79 °W. It slopes gradually shallower in a series of 

 humps farther to the west until it reaches 250 m between 140° and 150° 

 W beyond which the 34.70%o isohaline slopes into deeper water. Sec- 

 tions of the salinity maximum lie below 1250 m between 65° and 

 130°W. The wedge of lower salinity water from the Eoss Sea forces 

 the maximum salinity layer into the upper water level between 350 m 

 and 750 m at 138°W to 150°W. 



