FY 1981

Drift characteristics of Northeastern Bering Sea ice during 1980

Pease, C.H., and S.A. Salo

NOAA Tech. Memo. ERL PMEL-32, NTIS: PB83-112466, 78 pp (1981)

An ice drift experiment was conducted in the northeastern Bering Sea for eight days during February and early March 1980. Current, meteorological, and ice floe data from two floe sites were collected serially and compared to regional observations. The floe initially drifted eastward because of the dominant eastward current and generally opposite the weak northeasterly wind. After a day, the floe abruptly changed drift direction toward the northwest concomitant with a reversal in current direction. This event preceded the local change in wind direction which accompanied the passage of a low-pressure center over the eastern Bering Sea. During this storm, northward currents and southeasterly winds caused the floe to accelerate toward the Bering Strait. After the storm, the winds dominated the floe drift and the currents relative to the ice were weak. During and after the passage of the storm, a major shearline in the pack ice was observed from Sledge Island toward the southeast to within 75 km of the Yukon River Delta, indicating that ice in Norton Sound was cut off from the main drift stream. The ice floes were characteristically a meter thick with a few centimeters of snow, gaining 15 cm of snow during the storm. Ice concentrations averaged 9–10 tenths and the pack was generally comprised of big to vast floes, although new-to-young ice was observed in the Nome polynya before the storm, along the shear zone, and in a number of leads. A vector representation of the relative velocity fields is presented with a discussion of the forcing terms on the floe drift. The analysis of rotation angles of the wind and current to the floe drift and the relative speeds suggest that the current has a very strong influence on ice drift in this region.