a geographic belt in the northern hemisphere, bounded by the arctic belt in the north and by the temperate belt in the south. The southern boundary of the subarctic belt in the ocean is within the range of distribution of seasonal ice. The climate is cold; the average temperature in the warmest month is 5°–10°C, while in the coldest months the temperature ranges from –5°C in the west to –30°C or –40°C and even –50°C in the central parts. In summer, westerly shifts of temperate air masses and intensive cyclonic activity predominate, while in winter there are shifts of arctic air masses, and the atmosphere is in an anticyclonic state. Annual precipitation, chiefly in solid form, averages 300–500 mm, which exceeds evaporation. The snow cover lasts more than eight months, and the ground freezes deep. Polygonal ground, hydrolaccoliths, and solifluction land-forms are characteristic of the microrelief and mesorelief.
The division of the subarctic belt into geographic zones is based mainly on summer thermal conditions; therefore the zones are basically circumpolar. The tundra zone is found in the colder part of the belt, to the north, while the forest-tundra zone is in the warmer, southern part.
The North American and European-Asiatic parts of the subarctic belt each have two maritime sectors and one continental sector. In the ocean all processes are clearly seasonal, being related to the glacial regime. The abovezero summer temperatures near the ocean surface and the high level of oxygen and the prolonged presence of light create favorable conditions for the development of plankton, which accounts for the abundance of commercial fish and other animals.
REFERENCESGrigor’ev, A. A. Subarktika, 2nd ed. Moscow, 1956.
Sovetskaia Arktika: Moria i ostrova Severnogo Ledovitogo okeana. Moscow, 1970.
Okean. [Collection of articles.] Moscow, 1971. (Translated from English.)
Riabchikov, A. M. Struktura i dinamika geosfery, ee esteslvennoe razvitie i izmenenie chelovekom. Moscow, 1972.
E. V. MILANOVA