IV. BRANSFIELD STRAIT - DRAKE PASSAGE, OCEANOGRAPHY 



A. General 



Bransfleld Strait is a comparatively narrow passage between the 

 northern tip of Palmer Peninsula and the South Shetland Islands. Its 

 width, between Trinity Island to the south and Deception Island to the 

 north, is approximately 60 miles. This strait is almost always ice 

 free during the greater part of the Antarctic summer. 



To the north of the South Shetland Islands lies Drake Passage, which 

 separates Antarctica from South America by a distance of about ^50 miles. 

 Water circulation through the passage is from west to east induced by the 

 West Wind Drift. The water passing through this passage is considerably 

 warmer than that flowing through Bransfield Strait. The Antarctic 

 Convergence, as observed on this survey, was located between 55*15'S and 

 55°30'S. 



B. Physical Properties 



Three oceanographic stations (18, 19> and 20 ) were occupied across 

 Bransfield Strait aboard GLACIER on 10 March i960 (Pig. k). Soundings 

 for these stations were 622, 1,189 sad k$k meters, respectively* Figure 

 10 presents vertical distribution of temperature, salinity, density, and 

 oxygen. The physical properties in the upper 100 meters of this cross 

 section correspond closely with continental shelf water of low tempera- 

 ture and salinity values and high oxygen content. Below this level to 

 maximum sampling depths, a transition toward Bottom Water appears with 

 evidence of possibly a southern boundary of Circumpolar Water near 

 station 20. 



Ten stations were occupied by GLACIER across Drake Passage during the 

 period 12 and 13 March along the 057^ meridian from 60°S to approxi- 

 mately 5^"S« Sonic depths for stations 21 through 28 were around It-, 000 

 meters with the depth shoaling to 82 meters on station 30. Figure 11 

 presents" vertical distribution of temperature, salinity, and density. 



Figure k shows ships' tracks and station locations for both of these 

 areas. 



1. Bransfield Strait (Figure 10 ) 



a. Temperature 



Surface temperatures ranged from 0.50 to 0.75 °C> with the 

 minimum temperature noted at station 19. A slight negative gradient, 

 resulting from surface seasonal warming, occurred to about 100 meters 

 where minimum temperatures were observed. Below this, values increased 

 slightly with depth to the maximum depths sampled. 



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