Subantarctic Belt

Subantarctic Belt 

(also subantarctic low-pressure belt), a geographic belt in the southern hemisphere, bounded by the temperate zone in the north and the antarctic belt in the south. The entire belt is oceanic and is situated within the limits of seasonal shifts of the arctic front between 65°–67° S lat. and 58°–60° S lat. Seasonal changes of air masses are characteristic, with antarctic air predominating in winter and air from the temperate latitudes in summer. In winter the average air temperature ranges from – 5°C in the north to – 15°C in the south, and the water temperature from – 1.5°C to – 2°C. In summer the air and water temperatures range from 0°C to 2°C. In winter there are snow-covered floating ice and numerous icebergs. Blizzards, snowstorms, and fogs are frequent. The harsh climate is aggravated by high air humidity and by strong storm winds caused by high barometric pressure gradients between the cold continent and the warmer ocean. Annual precipitation is 500 mm, primarily in the form of snow. In summer the water is free of ice. The water salinity changes little during the year, varying from 33 to 34 parts per thousand. Considerable wind turbulence and swell are characteristic; wave heights vary from 2–5 to 10 m.

Plankton is abundant (100–200 mg per cu m), and numerous large planktonic crustaceans serve as food for fish, birds, and mammals. The subantarctic belt is a major whaling region. The few islands in the belt feature lichens, grasses, and shrubs.

REFERENCES

Treshnikov, A. F. Osobennosti ledovogo rezhima Iuzhnogo Ledovitogo okeana. Leningrad, 1963. (Tr. Sovetskoi antarkticheskoi ekspeditsii, vol. 21.)

L. I. KURAKOVA