Current variability under landfast sea ice in Lützow-Holm Bay, Antarctica

Abstract

Current measurements were made under landfast sea ice in Lützow-Holm Bay, Antarctica, in 1991. In spite of no direct wind forcing and negligible thermohaline forcing, currents with a magnitude of 0.1-0.3 m s-1 were observed. It is suggested that current variability strongly depends on the extent of the landfast ice on the eastward continental shelf. Before the fast ice edge extends to the shelf break the current at Ongul Strait, located near the continental coast, is highly coherent with the wind with a time lag of 1-1.5 days and somewhat coherent with the adjusted sea level with no time lag at periods of 6-8 days. After the fast ice edge is stably located along the shelf break the current is not at all coherent with the wind or sea level. We infer that the variability at periods of 6-8 days is mainly due to the first-mode shelf wave excited by the wind stress over the eastward continental shelf. The direction of the prevailing current at Ongul Strait changed drastically from southward (the same direction of the wind) to northward in May, although the prevailing wind direction did not change. This change in timing coincides with the rapid development period of the fast ice extent. Copyright 2000 by the American Geophysical Union.