HYDROLOGY OF THE BRANSFIELD STRAIT 19 



The temperatures and salinities of the surface water at the stations in this survey show 

 the effect of summer conditions in the Bransfield Strait. The surface water is probably 

 at its maximum temperature in February and the approach of autumn is not reflected in 

 the surface temperatures until a month later in the year. 



The surface charts show a common agreement: warm light water is seen near the 

 coast of the South Shetland Islands and at the south-west end of the strait, with dense 

 colder water close to Trinity Peninsula. Poorly saline water of comparatively high 

 temperature, whose origin is the Bellingshausen Sea, is seen entering the strait between 

 Low Island and Smith Island and continuing into the strait, causing warmer and less 

 dense water at St. WS 390 on the line between Livingston Island and Trinity Peninsula. 

 Another inflow of poorly saline warm water occurs between Smith and Snow Islands. On 

 the line from King George Island to Trinity Peninsula the salinity of the surface water 

 increases normally towards Trinity Peninsula as far as St. WS 384. At Sts. WS 385 and 

 WS 386 an accumulation of water of considerably lowered salinity occurs in the surface 

 layer. Thus a difference of 0-43 °/ 00 is seen in the salinity observations between the 

 surface and 30 m. at St. WS 386. From St. WS 386 to the coast of Trinity Peninsula 

 the surface salinity then increases as usual. The accumulation of low salinity water in 

 the upper layers at St. WS 385, and in particular at St. WS 386, is also reflected in the 

 lower phosphate contents of the surface waters at these stations. It is remarkable 

 because normally the surface salinity at these two stations would reflect the influence 

 of the cold and more saline Weddell Sea water. No trace of the low salinity is found in 

 the section from Livingston Island. The water in the surface layer at Sts. WS 385 and 

 WS 386 is therefore surrounded by more saline water, and we think its occurrence can 

 only be explained by the assumption that considerable ice melting must have recently 

 occurred in this vicinity and that the diluted water had not yet been transported away. 

 Consequently slack water conditions prevailed and layering occurred, leaving, in the 

 absence of eddy motion and vertical mixing, a shallow discontinuity layer. A very 

 strong north-east setting current was observed at St. WS 383 but was no longer 

 present at St. WS 384. The topographical charts show that heavy water is present at 

 St. WS 384 and that this station is on the right-hand side of the north-east flowing 

 current at St. WS 383. An anti-clockwise eddy at St. WS 386 is shown in the topo- 

 graphic chart of the surface, and in these circumstances light water would be accumu- 

 lated at this station. The whole temperature series at St. WS 386 is also remarkable, the 

 many changes between relatively warm and cold water exhibited by the vertical 

 observations are confusing. A similar occurrence, however, has been noticed by us 

 before in the Bransfield Strait and is probably a direct consequence of a succession of 

 ice freezings and meltings at this particular station whereby an abnormal temperature 

 series was established. 



The vertical sections of salinity, temperature and density (o- ( ) of the section from 

 King George Island to Trinity Peninsula are shown in Figs. 17-19. St. WS 385 was 

 taken in a very strong north-east setting current which caused large stray on the water- 

 bottle wires. Unprotected thermometers which give an indication of the true depth were 



3-2 



