Drifter measurements of surface currents near Marguerite Bay on the western Antarctic Peninsula shelf during austral summer and fall, 2001 and 2002

We deployed 24 satellite-tracked surface drifters near Marguerite Bay on the western Antarctic Peninsula shelf during March-May 2001 and February-April 2002. The WOCE-style drifters featured holey sock drogues centered at 15 m and were located about 20 times per day by Service ARGOS. Analyses of the drifter tracks show a coastal current that 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 early presence of sea 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 due to the sea ice coverage to the south. A mean drifter current speed of about 10 cm s(-1) was observed in the coastal current with a maximum speed of about 20 cm s(-1) during periods of strong wind stress. An intermittent northeastward current was observed near the shelf break. The drifter tracks also show that intermittent near-inertial currents are common in Marguerite Bay and over the adjacent shelf during ice-free conditions. These counterclockwise oscillations had periods near the local inertial period (roughly 13.0 h) and speeds of 5-20 cm s(-1) with a tendency for smaller amplitudes within Marguerite Bay. (C) 2004 Elsevier Ltd. All rights reserved.