Observing the advection of sea ice in the Weddell Sea using buoy and satellite passive microwave data

Abstract

This study examines the progress and behavior of an area of sea ice as it drifts from the southwestern Weddell Sea by using data from four buoys tracked by Nimbus 6 and concurrent ice concentrations retrieved from Nimbus 7 scanning multichannel microwave radiometer data. It covers the entire growth season of 1980. The overall drift characteristics, and their relationship to ice edge displacement, are examined within the framework of four zones. Three phases are identified in the large‐scale behavior of the Weddell sea ice cover, namely, a rapid equatorward and eastward advance, a quasi‐equilibrium phase, and a period of rapid recession. A broad division is made between the sectors to the east and west of 35°–40°W in terms of the nature of ice edge advance. Transient departures from the mean northward advection are linked to the passage of cyclones; certain such events may be significant in terms of the formation and maintenance of the region of highly consolidated perennial ice observed in the western Weddell Sea. Mean daily drift rates (up to 0.9 m s−1) from within the central‐western Weddell pack are high in 1980, particularly early in the growth season and when compared with rates to the west of 50°W. Outbreaks of cold continental air alternate with incursions of relatively warm air from the north; warm conditions are recorded as far as 1200 km in from the ice edge in winter. Closed loops in the buoy trajectories, which are clockwise to the south of 63°S, reverse to become anticlockwise to the north. Mid‐ocean islands impede the eastward progress of the ice. A coherence is noted in the response of the buoys to the passage of storms, even though the buoys separated by a distance of over 100 km.