on 25 and 26 February 1955. As in the South Pacific, a similar double 

 stop in temperature rise was noted (fig. 13) • The first rise of 36° 

 to hh° F. occurred between 52°30' and 5l°U0' S, and the. second rise of 

 U5° to 53° F. between 1^9° and ii8° S. Traveling north, salinity values 

 and air temperatures began to rise proceeding the rapid rise in siirface 

 water tamperatures. An iceberg hZ miles in length was passed at close 

 range just prior to crossing the convergence. Melt water from this 

 iceberg caused the sudden dip in salinity noted at about 53°^0' S. 

 Surface water density decreased as lower latitudes were gained. 



Figure lU shoifs a vertical section of temperature across the 

 Atlantic Antarctic Convergence, As shown in the vertical section 

 across the Pacific Antarctic Convergence, the 37° F. isotherm serves 

 well as a boimdary between the contrasting water masses. Water tempera- 

 tures below 32° F, are conspicious near the surface layers for some 

 distance north of the convergence and are absent south of the convergence. 



c. Comparison of Pacific and Atlantic Antarctic Convergence— 

 The Antarctic Convergence is very strikingly portrayed in both the South 

 -Pacific and South Atlantic sections. Both sections show the rapid in- 

 crease in surface water temperatures that mark the convergence, and the 

 second step or rise in temperatures to the north of the convergence. 

 Lower salinities occur in the colder surface waters immediately south 

 of the convergence zones. Density gradually decreases to the north as 

 warmer water is encoiintered in the surface layer. On the other band, 

 the Atlantic Antarctic Convergence is found farther north and is 

 characterized by cells of colder vr.iter \mder +^he surface layer immedi- 

 ately north of the convergence. The cold vrater cells and the marked 

 irregvilarity of the contours suggest the mixing of Antarctic Inter- 

 mediate Water wj th deeper waters, 



2, Ross Sea Area 



Figure 15 shows bathythermograph traces for observations in the 

 Ross Sea area during Jsjfiuary 1955. Bathythermograph casts 12U and 162 

 were taken v.'liile xinderway in open water, hence the shallow depth of 

 the tracej the others vrere taken whil.e the ship was motionlesc. BT 

 niiraber 15L! off Cape Colbeck, was taken while the ATKi\ was waiting for 

 a shift in ice conditions to free herseLf from the conooiidated ice 

 in that area on 19 January. The water was almost isothermal to a 

 depth of 900 feet at this point. 



3, Cape Colbeck to the Bransfield Strait Area 



Representative BT traces for the area east of Cape Colbeck during 

 late January 1955 are presented in figure 16, Host of these casts were 

 taken in water which was 2,000 fsihoms deep or greater; nunber 213, off 

 Peter I Island, was taken in only 1,200 fathoms of water and number 197 



37 



