108 U.S. NATIONAL MUSEUM BULLETIN 291 



waters from about 600 to over 2500 m and represents a large segment of 

 Antarctic Circumpolar Water. The high salinity tongue penetrates 

 from the north and represents the southern limits of the highly saline 

 North Atlantic Deep Water. Salinities greater than 34.80%o penetrate 

 the antarctic region 2000-2500 m under the convergence at the surface 

 as far as about 48°S. South of this zone the saline water ascends to 

 shallower depths and becomes somewhat dilute southward. The 34.72%o 

 isohaline is continuous nearly to 60°S ; the 34.73%o isohaline is continu- 

 ous to 54°30'S and a core of 34.73%o water occurs at 1000-1750 m be- 

 tween 55° and 58 °S. This high salinity water of Atlantic origin remains 

 as a constant feature of the Antarctic Circumpolar Water mass and is 

 evident even in sections from the eastern Pacific. The 25 °W salinity 

 section does not extend very far north, but the tongue of high salinity 

 water at 500-1000 m is the southern edge of the salinity core that is so 

 prominent in the 35 °W section. 



The plot of sigma-t values (fig. 24) shows high densities in deeper 

 waters coincident with the high salinities and low temperatures. Most 

 of the Antarctic Circumpolar Water mass has densities greater than 

 sigma-t =27.80. 



The distribution of oxygen along 35 °W (fig. 23) reveals the oxygen 

 minimum layer at 600-800 m in the antarctic region. Minimum values 

 range from 3.98 ml/L to 4.83 ml/L with the higher values located 

 around 55°S. The minimum value just north of the convergence is 4.16 

 ml/L and it is located at a depth of 800 m. Concentrations increase 

 gradually with depth below the layer of oxygen minimum. 



Eltanin Cruises 9 and 12 covered the area included in the sections 

 for 35 °W. During Cruise 9 twenty 3-meter IKMT tows were made in 

 the region under discussion, but five of these were at depths shallower 

 than 500 m where B. dbyssicola generally is not found. Eight of the 

 remaining tows captured B. ahyssicola. Many IKMT tows in the right 

 depth range were taken during Cruise 12 but specimens from only 

 two tows have been received. Both of these samples contained B. ahys- 

 sicola. The ten captures, taken between 31° and 38°W, are plotted 

 on the 35°W oceanographic sections. Eight captures of 12 specimens 

 were made between 55° and 60°30'S. Six captures of these were made 

 where the water temperature ranged from just under 1° C to just over 

 1.5° C in depths from 800-1700 m. Three tows were taken in water 

 around 0.5° C; the specimen at 60°30'S could not have come from 

 a temperature greater than 0.5° C (the "simultaneous" temperature for 

 tliat location and depth, 1281 m, was 0.17° C) ; the other specimens 

 in this temperature were taken in water close to the 0.5° isotherm. The 

 simultaneous temperature for the deepest specimen is 0.65° C, and for 

 the capture at 2214 m (two specimens) it is 0.34° C. The 2214 m cap- 



