Drifter Measurements of Surface Currents near Marguerite Bay

on the West Antarctic Peninsula Shelf

Robert C. Beardsley, Richard Limeburner, W. Breck Owens

Woods Hole Oceanographic Institution

We deployed 24 satellite-tracked near-surface drifters near Marguerite Bay on the West Antarctic Peninsula shelf during the 2001 and 2002 austral summers. Analyses of the drifter tracks show that near-inertial currents (period ~ 13 hr) with speeds of 5-20 cm/sec are common in Marguerite Bay and over the adjacent shelf. On longer time scales, a coastal current flows toward the southwest along the west coast of Adelaide Island and into Marguerite Bay near the southern tip of Adelaide Island, then flows clockwise around the Bay near the coast, and finally exits the Bay near Alexander Island. This coastal current flowed along the eastern boundary of Marguerite Bay in 2001, but across the central part of the Bay in 2002 due to the presence of ice in the southern half of the Bay. The outflow from the Bay continued along the coast of Alexander Island toward the southwest in 2001, but was directed northwestward across the shelf in 2002 because of the ice coverage. A mean drifter current speed of about 10 cm/s was observed in the coastal current with a maximum speed of about 20 cm/s during periods of strong wind stress. An intermittent northeastward current was observed near the shelf break during austral summer.