BATHl^PELAGIC SQUID BATHYTEUTHIS 101 



Water and Antarctic Bottom Water. In the boundary zones the Deep 

 Water mixes witli tlie Intermediate and Bottom Waters so that when 

 it reaches tlie hi^h southern hititudes of the Antarctic Ocean it is some- 

 what dihited and cooler. Nevertheless it retains its characteristic high 

 salinity, and this mass of saline, "warm" Deep Water rises toward 

 the surface above the descending Antarctic Bottom Water and con- 

 tributes to the formation of the Antarctic Circumpolar Water. The 

 process in the Indian and Pacific Oceans is similar though less pro- 

 nounced, and deep water in these oceans has a strong component of At- 

 lantic Deep Water. The location of the Antarctic Convergence is 

 marked as distinctly by the positions of the Deep and Bottom Waters 

 as by the submergence of the Antarctic Surface Water ; the isotherms 

 and isohalines at great depths slope as steeply as those near the surface 

 (Deacon, 1963). 



The concentration of oxygen in the antarctic region is generally high 

 and probably never goes below 3-3.5 ml/L. Around the antarctic region 

 the oxygen minimum layer is located between 600-1200 m. In the 

 Drake Passage the concentration is relatively low, but eastward in the 

 Scotia and Weddell Seas the oxygen content increases and the oxygen 

 minimum layer is shallow and has a high value. Farther eastward the 

 concentration gradually diminishes in the minimum oxygen layer 

 and in the Deep and Bottom Waters. In the northern subantarctic 

 region the oxygen minimum layer lies in the Deep Water mass at 

 around 2000 m, but it rises to shallower depths farther south. Antarctic 

 Intermediate Water is high in oxygen content as it leaves the surface, 

 but the oxygen concentration diminishes northward and with depth. 

 In most areas, and particularly north of the Weddell Sea the Antarctic 

 Intermediate Water is characterized as an oxygen maximum which 

 overlies the oxygen minimum of the Deep Water. Antarctic Circum- 

 polar Water generally has more oxygen than Deep Water to the north. 

 Antarctic Bottom Water has very high oxygen concentrations because 

 it has so recently been in contact with the surface. In the Weddell Sea, 

 oxygen concentration may reach 7 ml/L at the surface. Bottom Water 

 has concentrations as high as 5.5 ml/L (Sverdrup et al., 1942). 



The concentrations of nutrient salts in the Antarctic Surface Waters 

 rarely fall below the winter maxima of temperate regions (Clowes, 

 1938) . The surface waters of the subantarctic region have less nutrients, 

 but in deeper waters between the Antarctic Intermediate Water and 

 the Deep Water nitrates and phosphates appear to be regenerated; 

 this boundary layer also conforms to the oxygen minimum, so that the 

 region probably is an area of mortality and decomposition of phyto- 

 plankton. The decomposition releases nitrates and phosphates to the 

 southward-moving warm Deep Water, and in the antarctic region 



