HYDROLOGY OF THE SOUTH ATLANTIC 195 



tinuities and very thin surface strata are often found on fine days in the vicinity of icebergs 

 or pieces of drift ice. Sudden jumps of as much as 4^ C. in surface temperature have 

 been recorded by the continuous thermograph when such patches have been crossed. 

 Such thin surface strata do not last, and are only found on calm sunny days. They break 

 up, and help to reduce the salinity and increase the temperature of the surface layer. 



To show the distribution of temperature and salinity in the surface layer in the 

 Falkland Sector, charts have been prepared giving the average temperature and salinity 

 of a surface stratum 100 m. deep. They are based on a survey which was completed in 

 seven weeks, between October 25 and December 13, so that they are not appreci- 

 ably distorted by the changes which had been taking place whilst the work was being 

 carried out. The distribution of temperature and salinity in the Falkland Sector for 

 different seasons of the year and for different years will be published later, when allow- 

 ance has been made for such changes. The isotherms are shown in Fig. 12. 



The cold water west of Graham Land belongs to the Bellingshausen Sea current. 

 On the northern side of the current the sea is warmer, and the temperature rises 

 slowly until there is a jump of about 3° C. at the Antarctic convergence. The path of the 

 current can be followed by the low temperatures to which it gives rise north of Elephant 

 Island. The cold water east of Graham Land belongs to the Weddell Sea current. The 

 temperatures observed in Weddell Sea water were not so low as those recorded in 

 Bellingshausen Sea water : in the Bellingshausen Sea the temperature at the edge of 

 the pack-ice was —1-63 to — i-89°C., and in the Weddell Sea — i-ig to — i-5i°C. 

 The northerly movement of Weddell Sea water is shown by the low temperature of the 

 eastern half of the Scotia Sea. The bend of the isotherms east of South Georgia shows 

 how Weddell Sea water flows round the north-east coast. 



The shape of the i ° and 2° isotherms shows approximately the path of the Bellings- 

 hausen Sea water north of the Scotia Sea. Near the western end of South Georgia the 

 isotherms bend southwards, so that the south and west of the island are influenced by 

 this warmer water which has its origin in the Bellingshausen Sea and has been warmed 

 on its way northwards. 



The Antarctic convergence in November follows approximately the 3^ C. isotherm 

 in the west ; it lies where the i °, 2°, and 3'' isotherms crowd together in the Drake Passage. 

 Farther north, where the convergence is not so sharp, it follows the 3-5° isotherm and 

 lies between the 3° and 4° isotherms. The total range of the average temperature of a 

 surface stratum 100 m. deep, which in November is almost uniform, is from — i-86° C. 

 in Bellingshausen Sea water to about 3-5° C. at the Antarctic convergence north of 

 South Georgia. 



The salinity of the 100 m. surface layer is shown in Fig. 13. It is reproduced prin- 

 cipally to show the difference in salinity of the Bellingshausen and Weddell Sea waters. 

 The lowest salinities are those on the northern side of the Bellingshausen Sea current, 

 and the diagram indicates that a belt of water of low salinity exists just south of the 

 convergence. The salinity of the water in this belt of minimum salinity decreases from 

 about 34-847oo ^^ 8°° W to 33-797oo farther to the north-east, where the current has 



