Further south, surface temperatures continued to decrease 

 particularly in areas of pack ice and icebergs. On the northern perim- 

 eter of the Weddell Sea the depth of the temperature minimum extended 

 from the surface to 50 meters, unless the pack ice had disintegrated 

 and the resultant heating from summer insolation had begun. 



Within the pack ice itself a series of stations southward showed 

 a temperature-maximum layer, with temperatures between 0.5°C and 1.0°C 

 at a depth of about 300 meters (Fig. 4). This layer is apparently 

 the remnant of the warm deep layer, now at relatively shallow depths, 

 surrounded by colder water above, below, and to the south. This product 

 of the warm, deep water is now termed the Antarctic Circumpolar Water. 



Within the Weddell Sea, water temperatiires were generally iso- 

 thermal over shelf area with minimums of -2.0°C. Bathythermograph 

 traces in the Weddell Sea itself showed this isothermal water over 

 the shelf areas with slight surface warming when leads were large 

 enough and stable enough to permit heating from insolation. In the 

 deeper areas just outside of the Weddell Sea limits, the typical 

 summer surface situation was present, with the warm, deep layer under- 

 lying the colder Antarctic Surface Water. The surface itself was 

 warmed by summer insolation if ice was not present. No bathythermograph 

 lowe rings were possible in the deeper area within the Weddell Sea. 

 Seasonal warming of the surface waters within the ice-filled Weddell 

 Sea appeared to be an intermittent phenomenon, dependent upon the 

 presence and longevity of leads and polynyas.. 



In summary, the temperature mechanics of the Weddell Sea area appear 

 to be as follows: The water that is chilled along the Antarctic Shelf 

 areas flows down over the Antarctic Continental Slope to form Antarctic 

 Bottom Walter with a northward set. It thus passes londer the Antarctic 

 Circumpolar Water and eventually imder the warm, deep water. Meanwhile, 

 the warm, deep water has a southward set, and rises at the Antarctic 

 Convergence to shallower depths where it mixes with adjacent waters and 

 forms the Antarctic Circumpolar Wkter. The upper layers of the Ant- 

 arctic Circumpolar Wkter are chilled by the cold Antarctic winters, and 

 are mixed-out and diluted with great quantities of melt water and pre- 

 cipitation. The water mass is then called the Antarctic Surface Water. 

 Slammer heating may slightly rewarm the surface after melting or moving 

 ice exposes the water to insolation, and a temperature-minimum layer is 

 thus isolated just above the Antarctic Circumpolar Water. In winter 

 the surface is again cooled and vertical mixing takes place, producing 

 isothermal cold water overlying the Circumpolar Water. 



The temperature structure for a typical sxmmer station over the 

 Weddell Shelf is illustrated by Station S.I. -24. Extensive pack ice 

 prevented extensive surface warming. This is an extremely simplified 

 and generalized explanation, and refers only to north-south components 

 in the water movement. It should be remembered that the major surface 

 currents are circumpolar, following the great wind belts. Discon- 

 tinuity in the bottom topography and fluctuating meteorological con- 

 ditions will create local variations that may be temporarily adverse to 

 the above explanation. More data are required before the situation 



