As stated previously, the sea surface temperature chart 

 (see fig. 12) is based on observations made during four differ- 

 ent months. In some regions, observations were repeated 

 so that the seasonal change could be investigated. A summary 

 of the month-to-month changes observed are shown in table 6. 



ANTARCTIC CONVERGENCE 



General. Proceeding southward from the region of warm 

 surface water in the low latitudes, one first encounters gradual 

 decreasing temperatures. However, in a region between 

 55°S and 65°S, the temperature decreases markedly within 

 a short distance. Beyond this region of strong horizontal 

 temperature gradients, the surface temperatures remain 

 rather constant and near the freezing point. This boundary 

 is a region where part of the cold antarctic surface water, 

 brought northward by the transverse circulation created by 

 the westerly wind system, sinks below the warmer water 

 transported southward by the thermohaline circulation which 

 dominates in the subantarctic region. This area of sinking 

 is called the Antarctic Convergence . 



As indicated in the section, "Icebergs and Sea Ice," the 

 convergence was quite apparent as an abrupt water-mass 



25 



