Il. OCEANOGRAPHY 
A. Water Types of the Pacific-Antarctic Area 
The Pacific-Antarctic waters can be divided into two characteristic layers; 
Antarctic Upper Water, with low temperatures and salinities, and Antarctic Deep 
Water, with maximum temperatures and salinities and a gradual decrease of these 
properties to bottom. The boundary between these two layers is readily recogniz- 
able by a transition zone, where a rapid increase in temperature and salinity 
appears over a short-depth interval. According to Deacon, the Antarctic Upper 
Water can be described briefly as follows: A layer 100 to 250 meters thick is found 
all around the Antarctic seas. In winter, the water column is practically homogeneous. 
Temperature increases northward, from -1.9°C in the southern half of the zone, to 
between 0 and 1°C at the Convergence. In summer, a surface layer, Antarctic 
Surface Water, is formed, which has a higher temperature and lower salinity than 
Winter Water due to summer heating and ice melting. 
The deeper layer of the Upper Water has been called Antarctic Winter Water by 
Mosby because this layer has nearly the same characteristics as the previous winter's 
Upper Water. Winter Water is significant in that it has a low temperature, a salinity 
with a lower gradient than exists in the transition layers above and below, and a 
salinity profile that often has a break in it. Below this layer of Antarctic Upper 
Water, a narrow transition layer with steep positive temperature and salinity gradients 
rapidly leads into Antarctic Deep Water. 
Just south of the zone of strong negative surface temperature gradient, referred 
to as the Antarctic Convergence, one finds within the Deep Water three water types: 
Upper Deep Water, Lower Deep Water, and Bottom Water . 
Upper Deep Water has a temperature of 2.0°C, or higher, and a salinity around 
34 .68%,,. This Upper Deep Water is found south of the Convergence, just below the 
Winter Water. It is replaced 125 to 150 miles south of the Convergence by Lower 
Deep Water, which is undergoing transition to Antarctic Circumpolar Water. 
Values of salinity and temperature necessary for water to be identified as Lower 
Deep Water are: temperatures greater than 0.5°C and a band of maximum salinity 
slightly greater than 34.7%. These values are the same as those generally assigned 
to Antarctic Circumpolar Water. Therefore, for purposes of discussion, another 
restriction must be placed on Lower Deep Water, that of depth. In order for water 
to be classified as Lower Deep Water within the Antarctic Zone (south of the 
Convergence), its core of maximum salinity must be at a depth of about 2,000 meters. 
