From the edge of the continental shelf to a 

 depth of 2000 meters, a relatively warm, saline 

 water mass exists in the Weddell Sea Coastal 

 Current (fig. 2). This water mass, called Warm 

 Deep Water by Deacon (1937), is the major 

 mass in the Coastal Current. We found it char- 

 acterized by above-zero temperatures (0.0 to 

 0.6 °C) and salinities of 34.65 to 34.70%o. 

 Deacon (1963) stated that this water mass 

 consists of a mixture of Antarctic Circumpolar 

 Water and small amounts of North Atlantic 

 Deep Water. A. Gordon (personal communica- 

 tion) believes that part of the Warm Deep 

 Water is bottom water from the Southeast 

 Pacific Basin. 



Origin of the bottom water in the eastern 

 Weddell Sea (east of 35°W, fig. 2) is unknown. 

 The first detailed description of this water 

 mass, called Eastern Weddell Sea Bottom Wa- 

 ter, was given by Seabrooke, Hufford, and 

 Elder (1971). They found (during IWSOE 

 1968, 1969) the water mass properties to be 

 slightly different from Antarctic Bottom Water. 

 Results of the 1970 cruise (Table 2) substan- 

 tiate this. They also suggested that Eastern 

 Weddell Sea Bottom Water may be composed 

 of deep Circumpolar Water and recirculated 

 Antarctic Bottom Water, the Antarctic Bottom 

 Water being the largest component. Further 

 invesigation is necessary to determine the ori- 

 gin of this water mass. 



OXYGEN AND NUTRIENT DISTRIBUTION 



Dissolved oxygen was measured at all sta- 

 tions where Nansen casts were made. Concen- 

 trations exceeded 7.1 ml/1 on the continental 

 shelf, with maximum concentrations of up to 

 8.9 ml/1 occurring in the near-surface layers 

 (fig. 7). The Warm Deep Water had the lowest 

 dissolved oxygen content (4.2 to 4.9 ml/1) in 

 the Weddell Sea, and Eastern Weddell Sea Bot- 

 tom Water had slightly higher concentrations 

 (5.2 to 5.6 ml/1) (fig. 7). Percent saturation, 

 computed from solubility relationships devel- 

 oped by Green and Carritt (1967), varied from 

 90-97% in Antarctic Surface Water to 59-60% 

 in the Warm Deep Water and 62-68% in the 

 Eastern Weddell Sea Bottom Water. A possible 

 reason for the higher saturation values in 

 Eastern Weddell Sea Bottom Water is recircu- 

 lation of some Antarctic Bottom Water back 



into the Weddell Sea by way of the Antarctic 

 Coastal Current where it is mixed with deep 

 Circumpolar Water to form Eastern Weddell 

 Sea Bottom Water. Antarctic Bottom Water 

 formed in the Weddell Sea has a high satura- 

 tion value (about 80%, Hufford and Tennyson, 

 1970) because of recent contact of one of its 

 components (shelf water) with the sea surface. 

 According to Clowes (1938), the nutrient 

 concentrations in the Antarctic rarely fall be- 

 low the winter maximum concentrations of 

 temperate regions. Concentrations of the vari- 

 ous nutrients measured in the Weddell Sea sup- 

 port this. Ranges of concentrations found in 

 1970 were: 



inorganic 



phosphate 0.6-2.5 jag-at/l. 



nitrate — 



Nitrogen 14.0-33.0 ,ug-at/l. 



nitrite — 



Nitrogen 0.1-0.5 /ig-at/1. 



silicate — 



Silicon 32-125 ixg-at/\. 



In general the vertical distributions of the 

 nutrients in the Weddell Sea (figs. 8-13) fit the 

 classical description. On the continental shelf, 

 phosphate, nitrate, and. silicate concentrations 

 increased with depth to about 100 meters, then 

 remained fairly constant to the bottom (figs. 

 8-10). Off the shelf, the nutrients increased 

 with depth until a maximum was- reached be- 

 tween 800 and 1000 meters (figs. 11-13). Be- 

 low the maximum, concentrations decreased 

 slightly and then remained constant to the 

 bottom. 



To differentiate further the principal water 

 masses involved in the Weddell Sea Coastal 

 Current, preformed phosphate and nitrate con- 

 centrations were computed using the equations 

 of Pytkowicz (1968). Oxidative ratios were es- 

 timated from the changes in the concentration 

 of oxygen and nutrient ions. Preformed con- 

 centrations were computed only from samples 

 below 75 meters to eliminate discrepancies that 

 exist in the surface layer because of exchange 

 of oxygen with the atmosphere and mixing of 

 the surface waters. Mean values and varia- 

 tion about the mean were computed separately 

 for Antarctic Surface Water, Warm Deep Wa- 

 ter, and Eastern Weddell Sea Bottom Water 



