HYDROLOGY OF THE BRANSFIELD STRAIT 



37 



this layer was observed at the next station, but at Sts. 544 and 545 small temperature 

 inversions below the surface layer indicate the influence of the warmer water. At St. 545 

 a second though small temperature inversion is seen at 500 m., or some 100 m. above the 

 sea-bottom. This corresponds to a temperature inversion, also at 500 m., which occurs 

 below the vertically mixed surface layer at St. 546. The presence of such an irregular 

 temperature series at Sts. 538, 540, 545 and 546 and the proximity of these stations to 

 the flow of pack-ice from the Weddell Sea, would seem to indicate that the level of the 

 upper boundary of the warm deep water may be depressed during a season when 

 vertical mixing is particularly easy, i.e. when the surface is freezing or being cooled by 

 pack-ice. This would account for the depth of the lower temperature inversion. Sub- 

 sequently new relatively warm water may appear at a higher level and form the upper 

 inversion. An alternative explanation may be that warm deep water from the Weddell 

 Sea flows over the ridge between Elephant and Clarence Islands to Joinville Island, and 

 thus at these stations warm deep water from both the west and the east is present. 



STATION 



SNOW I. 



549 



550 



551 



552 



553 



SOOn 



IOOOn 



1500s 



34 I0%„ 



TRINITY I 



Fig. 48. Vertical section of salinity: Snow Island to Trinity Island, December 1930. 



Antarctic bottom water is found in considerable quantity at depths below the 

 intermediate temperature maxima. 



The vertical sections of the line between Snow Island and Trinity Island are given in 

 Figs. 48-50. The line cuts across the smaller basin at the south-west end of the 

 Bransfield Strait. The surface water at all the stations has been warmed by the sun. 

 A cold nucleus of the Antarctic surface water, with temperature below — 0-50° C, is 

 seen in the two most northern stations and at the station nearest Trinity Island. The 

 depth of the minimum temperature increases southwards from Snow Island. In general 

 the surface salinity increases towards Trinity Island. Near Snow Island, below the 

 depth of the cold nucleus of the surface layer, the temperature increases and reaches the 

 relatively high value of 0-50° C. in the warm deep water at 400 m. at St. 550. The rise 

 in the sea-bottom at Sts. 551 and 552 apparently prevents any appreciable amount of 

 warm deep water from appearing at further stations in the section, as the intermediate 



