Ice movement and distribution in the Bering Sea from March to June 1974

Abstract

Ice distribution and motion in the Bering Sea from March to June 1974 were observed by imagery from the NOAA 2 and 3 VHRR (very high resolution radiometer) satellites. The southerly ice edge was nearly constant in position from March to mid‐May, when ice disintegration had progressed to a point where the edge was undefined. Ice movement was southerly in response to northerly winds until late April, after which variable ice motion reflected variable winds. The southerly motion created regions of ice divergence south of islands and along east‐west trending southern coasts. In some areas such as the Bering Strait, water motion exerted sufficient stress on the ice to balance the wind.stress, resulting in stationary ice or northerly ice motion. The Bering Sea ice cover is conceptualized as northern source and southern sink regions connected by an intermediate zone of southerly ice motion. A mean observed southerly ice motion of 18 cm s−1 requires heat losses for ice formation of the order of 10 g‐cal m−2 s−1 or an order of magnitude greater if most ice is assumed to form in divergent areas covered by thin ice or that have open water. These values are in agreement with previous estimates of sea‐air heat flux in the Arctic.

Ecology and Biology of the Pacific Walrus,Odobenus rosmarus divergensIlliger

“…Complementary information on attendant ice, weather, and oceanographic conditions was derived principally from publications by the U.S. Navy (1946Navy ( , 1956Navy ( , 1958, Webster (1954), Schule and Wittman (1958), Zenkevich (1963), Hood and Kelley (1974), Burns (1975a, 1975b), Muench and Ahlnas (1976), and Brower et al (1977), as well as from my field observations and interpretations of satellite imagery and those, especially, of J. J. Burns and L. H. Shapiro.…”

Divergent movements of walrus and sea ice in the northern Bering Sea

“…Although the net transport of ice is southward during winter and early spring, the rate and direction of drift are not uniform throughout the pack ice (Burns et al 1981). Short-term (several days), small-scale fluctuations in ice drift occur, probably from variations in local winds, currents, and ice interactions (Muench & Ahlnas 1976).…”

“…Regions of relatively homogeneous ice habitats are formed each year in the Bering Sea from regionally specific winds, currents, and land configurations (Muench & Ahlnas 1976, Burns et al 1980, 1981. St. Lawrence Island is a major land form affecting movements of ice in the northern Bering Sea.…”

“…Although the net transport of ice is southward during winter and early spring, the rate and direction of drift are not uniform throughout the pack ice (Burns et al 1981). Short-term (several days), small-scale fluctuations in ice drift occur, probably from variations in local winds, currents, and ice interactions (Muench & Ahlnas 1976).Ice over the continental shelf affords walruses the ability to exploit benthic prey over large areas. It has been recognized that when walruses rest on moving ice they can be transported to new feeding areas (Fay 1982).…”

Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: Mean seasonal cycle

“…A conveyor belt mechanism, with a northern source, a southern sink, and an intermediate zone where ice is transported southward by northerly winds, has been proposed to explain the basic north-south structure using observations alone (Muench and Ahlnas, 1976;Pease, 1980). These satellite and in situ observations (Muench and Ahlnas, 1976;Pease, 1980;Wang et al, 2009;Stabeno et al, 2001), however, provide a limited perspective on what controls the seasonal extent and thickness of the ice. So numerical simulations are needed to better understand the dynamics and thermodynamics of these variations.…”