ANTARCTIC BOTTOM WATER 



99 



is a very mixed water. At the northern station in this basin (47I S) the bottom water 

 at 4500 m. had a phosphate content of 92 mg. Farther south there is a rise in the sea 

 bottom, and south of this rise the values at 4500 m. were 79 mg., 71 mg. and then, 

 in the southern part of the basin, 123 mg. It is difficult to see from what mixture of 

 waters this water of low phosphate content in the north of the basin is derived, because 

 south of the basin the phosphate content rose to 161 mg. at 3000 m. on the Cape Adare- 

 Easter Island ridge in 61 \° S with very little difference in temperature and in salinity. 

 Unfortunately section 13 made in 1934 from the Ross Sea to New Zealand (Plate XIX) 

 cannot be used to check the 1932 results owing to the fact that no observations were 

 made below 3500 m. in the critical position. 



Section 14 in 1932 from the ice-edge north of the Ross Sea to a position of 41 ° 03' S, 

 126 04' W in the central part of the South Pacific crossed the Cape Adare-Easter 

 Island ridge; the phosphate distribution is shown in Plate XXI. On the western side 

 of the ridge, where the bottom current is turned to the north, the bottom water had a 

 content of about 135-145 mg. On the eastern side of the ridge, between 150 and 

 140 W, the bottom water once more bends to the south and had a content of 145 mg. 



The remainder of the South Pacific Ocean cruise of 1932 along sections 15 and 16 

 (Plates XXIII and XXV) showed that the bottom water in the Antarctic zone between 

 no and ioo° W at a depth of 5000 m. had a phosphate content of about 135-140 mg. ; 

 this had decreased to i2omg. at 94 W. Between 8o° and 90 W in the southern part 

 of the sub-Antarctic zone the content at a depth of 4500 5000 m. increased northwards 

 from 122 mg. just north of the Antarctic convergence to 136 mg. in 55 18-4' S. 



In 1934 a considerable number of observations were made in the region of the pack- 

 ice in the South Pacific sector of the Southern Ocean. These showed quite clearly that 

 the bottom water had an eastward component of movement across the ocean. It increased 

 in temperature and decreased in oxygen content in its passage across the ocean, showing 

 that it mixes with warm deep water during this movement. The phosphate content at 

 4000 m. in the bottom water varied irregularly. On the cruise towards the west the extreme 

 range was 122 148 mg., but in general it varied from 135 mg. to 145 mg., increasing 

 slightly towards the east. On the return cruise towards the east higher contents were 

 encountered as the following figures show : 



Although the eastward cruise was made at a slightly higher average latitude owing 

 to the retreat of the ice in the interval between the cruises, the difference in phosphate 

 content in the bottom water must be due to another cause which at present we must 

 assume to be seasonal variation. It may be added that in November of the same year 

 nine stations situated between 8o° and no° W and within a short distance of the ice- 



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