Circulation patterns on the western Antarctic Peninsula shelf during 2001-2003

Moffat, C., R. Beardsley, R. Limeburner and B. Owens

We use moored array measurements, hydrographic surveys, and drifter observations collected during the 2001-2003 Southern Ocean GLOBEC field program to characterize the circulation on the western Antarctic Peninsula (wAP) shelf in and around Marguerite Bay. Tidal currents over the SO GLOBEC study area are small (<5 cm/s), with the K1, M2 components dominant. The K1 exhibits southwestward phase and energy propagation roughly parallel with the coast, consistent with the diurnal oceanic around-Antarctic Kelvin wave. The M2 tide propagates across the shelf and into Marguerite Bay, consistent with a more regional response. The observed tides compare favorably with a regional barotropic tidal model (Padman et al., this issue). Near-inertial motions are the largest contributor to the current variance at all measured depths with periods shorter than a day, and are thought to be a key player in the mixing of deep water into the surface layer (Hyatt et al., this issue). The subtidal circulation is composed by an active upper layer (<100 m) characterized by a seasonal, southwestward-flowing coastal current along the coast (Moffat et al., this issue) and northeastward flow along the shelfbreak associated with the larger-scale circulation (the Antarctic Circumpolar Current). The surface circulation on the mid-shelf is less coherent and weaker. The deep circulation on the shelf is strongly barotropic, with no seasonal variability and strongly influenced by the rugged and complex bathymetry of the WAP region. In particular, the Marguerite Trough is shown to channel deep oceanic water across the shelf into Marguerite Bay. It is also hypothesized that smaller structures in the seafloor provide a retention mechanism for particles in the deep layer.

STATUS UPDATE:

Title, abstract, and author list received on 06/23/05.