208 



DISCOVERY REPORTS 



LATITUDE 



2500m 



-3SOOm 



-4500m 



5000 



Text-fig. 15. Distribution of temperature (° C.) between 60° S. and 40 S. in the region of the 

 Greenwich Meridian, August 1938 (see Text-fig. 46 for station positions). 



The distribution of the pack-ice has a marked effect on the salinity and temperature of Antarctic 

 Surface Water, and varies from season to season. During the winter months of June to August, the 

 pack-ice extends to about 55— 56 S. (Mackintosh and Herdman, 1940); surface temperatures are very 

 low with a minimum of — i-8i° C. (Text-fig. 15) and the open water has a salinity of about 34-00 % 

 (Text-fig. 16). In summer the pack-ice melts, causing dilution of the upper layers; at the same time 

 absorption of radiation brings about an increase of surface temperature. As mixing proceeds well- 

 marked discontinuity layers are set up. These effects are shown in the hydrological sections for 

 January 1939, in which the surface temperatures are all above o-o° C. (Text-fig. 17), and a belt of 

 poorly saline water, with a salinity of less than 34 % , covers the surface to about 50-20 m. depth and 

 extends from the higher latitudes as far north as about 55 S. (Text-fig. 18). 



