9» 



DISCOVERY REPORTS 



In late April and early May 1934 between the South Sandwich Islands and 44 E an 

 average value at twelve positions for the phosphate content of the Antarctic bottom 

 water of a temperature of o-o° C. was 148 mg., whilst in the same area in February 

 1935 the average figure for nineteen stations was 138 mg. 



In May 1934 along section 6 from the ice-edge in 44 E northwards to the Crozets 

 (Plate X), an average phosphate content of the bottom water of o-o° C. and 34*67- 

 34-68 °/ 00 was about 160 mg. in the south of the Antarctic zone and about 140 mg. just 

 south of the Crozets ridge. North of this ridge the character and composition of the 

 bottom water is considerably changed, being more saline and warmer and containing 

 much less phosphate. Plate VII shows the phosphate content of Antarctic bottom water 

 along section 4 in late February and early March 1935. The phosphate content of bottom 

 water of temperature o° C. and salinity 34-67-34-68 °/ 00 was 140 mg. 



During the circumpolar cruise of 1932 the Southern Ocean was crossed diagonally 

 along section 7 between the ice-edge in 65 15' S, 48 43-7' E to Fremantle, Australia. 

 The phosphate section is shown in Plate XII. At the far south Antarctic bottom water 

 of o° C. and salinity 34-66-34-67 °/ 00 had a content of about 1 10 mg. Farther along the 

 section, towards the western side of the Kerguelen-Gaussberg ridge, the content increased 

 to about 125 mg., an increase which continued across the ridge. 



The phosphate content along section 9 south of Australia in late May 1932 is shown 

 in Plate XIV. The bottom water had a phosphate content of 130-135 mg. in the Antarctic 

 zone. North of the Antarctic convergence the content decreased to about 120-125 mg., 

 but here the bottom water was mixed with a large proportion of warm deep water. 

 At the southern end of section 10 from Melbourne to the ice-edge in 61 ° 25' S, 154 26' E 

 (Plate XV) the bottom water had a phosphate content of 134 mg., whereas at the deep 

 stations near Macquarie Island the contents were 121 mg. and 1 10 mg. respectively. 

 Deacon (1937, p. 114) has drawn attention to the fact that the bottom water only finds 

 its way into the deep basins south of New Zealand after being substantially mixed with 

 warm deep water : near Macquarie Island the relatively large increase of temperature and 

 decrease of oxygen and phosphate contents of the bottom water are accompanied by 

 only a small increase of salinity, and it seems as if the mixing with warm deep water has 

 taken place in a region where the salinity of the deep water has been reduced almost to 

 that of the bottom water by turbulent mixing which would have the effect of reducing 

 the phosphate content of the mixed bottom water found near Macquarie Island. 



The bottom water found in September 1932 along section 12 in the deep basin south- 

 east of New Zealand (Plate XVII), shows by its high temperature and salinity that it 



