edge of the continental shelf; this is best demonstrated by temperature and oxygen 

 values in Figure 3. 



The profiles for Station B-13 (Fig. 11) present graphically the characteristic 

 inverse relationship between the dissolved oxygen and the temperature curves, 

 which is typical of Circumpolar Water. Also shown are the great differences in 

 oxygen values between Upper Water and Circumpolar Water. Less extreme are 

 the differences between Antarctic Surface Water and Winter Water. 



At Station B-16 (Fig. 15), influence of modified Circumpolar Water is evident 

 at about 100 to 170 meters in the predominantly Winter Water column. Slightly 

 increased temperature and reduced oxygen values at that level are evidence of this 

 influence. Modified Circumpolar Water becomes apparent to the west along the 

 Ross Ice Shelf. Strong evidence of this intrusion appears at Station B-17 (Figs. 15 

 and 16). Here, a well-defined Antarctic Surface Water layer is underlaid by a 

 thin vestige of Winter Water (Fig. 16). This is borne out by a great decrease in 

 temperature and a slight decrease in salinity values at about 50 meters. Below this 

 depth to about 260 meters, Circumpolar Water has its greatest influence where 

 the temperature and salinity values increase and the oxygen is at its minimum. All 

 values indicate decreased Circumpolar Water influence below about 300 meters, 

 but intermediate salinity values throughout the lower portion of the water column 

 show the effect of Circumpolar Water intrusion. 



This penetration of warmer, oxygen -poor Circumpolar Water is present as a 

 tongue at about 200 to 300 meters (Figs. 4 and 15), with an eastward limit near 

 Station B-16. A vertical discontinuity of temperature and dissolved oxygen exists 

 at this site, with unmodified Winter Water extending eastward. Below the modi- 

 fied Circumpolar Water, Shelf Water occurs near bottom, and all data indicate 

 that contact and mixing of Shelf Water, modified Circumpolar Water, and Winter 

 Water take place at the deeper levels near Station B-16. West of this at station 

 B-22 (Fig. 17), Antarctic Surface Water extends downward to about 40 meters; 

 below this depth. Winter Water is altered by Circumpolar Water. The core of in- 

 fluence is at about 190 to 200 meters. Below this level, colder more dense Shelf 

 Water is present at about 420 meters and deeper . 



Figure 8 depicts a typical summertime structure of the water masses by a series 

 of stations extending from the edge of the continental shelf southwestward almost 

 to the Ross Ice Shelf. Circumpolar Water rises over the continental shelf edge 

 under the Winter Water that Is present offshore and extends beneath Antarctic Surface 

 Water almost as far south as the Ross Ice Shelf. Mixing between the intrusive mass 

 and the Winter Water takes place along the contact zone, and further mixing of 

 now modified Circumpolar Water occurs throughout the southern penetration under 

 Antarctic Surface Water, with accompanying changes in temperature and salinity 



23 



