II. ROSS SEA OCEANOGRAPHY 



A. General 



The Ross Sea is that body of water lying between Cape Colbeck and 

 Cape Adare , Antarctica. The sea is roughly triangular; having long 

 north to south reach in the west, a greater length in the Pennell Bank 

 area, and being rather narrow on the eastern side at Cape Colbeck. It 

 is bounded on the north by the continental slope (Fig. 3) and on the 

 south by the Antarctic Continent. The Ross Ice Shelf is the southern 

 boundary for the upper 200 meters (656 feet) of the water column, as 

 well as the southern limit for oceanographic observations. Along the 

 western boundary of the Ross Sea, several small ice shelves are present, 

 fed by the glaciers of Victoria Land. 



The Ross Sea has an average shelf depth of 500 meters (1,640 feet) 

 along its northern boundary (Fig. 3), with occasional deeper gaps or 

 canyons along the continental slope. South of this shelf boundary, deep 

 areas are present along the Ross Ice Shelf and the Victoria Land coast. 

 Superimposed on this uneven continental shelf are additional smaller 

 troughs and depressions. 



The Ross Sea is subject to annual climatic changes, ranging from heavy 

 ice cover and continuous darkness during the austral winter to almost ice 

 free conditions and continuous daylight during the austral summer. These 

 conditions cause the Ross Sea to approach equilibrium in the winter, but 

 to be unstable during the summer. 



In general, three water masses are present in the Ross Sea during the 

 summer with definite and definable characteristics. These water masses 

 are: (1) Antarctic Upper Water, (2) Antarctic Circumpolar Water, and (3) 

 Shelf Water. They may be defined by temperature-salinity relationships 

 as shown in figure 4. 



1. The upper water mass is divided into two water types during the 

 summer season. The temperature of the upper 100 to 200 meters (32 8 to 

 656 feet) is raised by increased solar radiation, and the salinity is re- 

 duced by the associated input of melt water. This warmer, less saline 

 layer is termed Antarctic Surface Water by Deacon (1937). The deeper 

 portion of the upper water mass retains the same characteristics acquired 

 during the winter season, therefore, this portion of the upper water has 

 been designated by Mosby as Winter Water (Mosby, 1934). 



2. Antarctic Circumpolar Water, present in the Ross Sea, is a south- 

 ward extension of Antarctic Deep Water (U.S. Navy Hydrographic Office, 1962) 

 As Antarctic Deep Water moves over the Ross Sea shelf, its characteristics 

 are modified from above by mixing with the Winter Water, and from below by 

 mixing with very cold and saline Shelf Water, Even through modified, the 



