Abstract

As part of the U.S. SO GLOBEC program, WHOI deployed an array of subsurface moorings to measure currents, water properties and sea ice motion, satellite-tracked drifters and isobaric floats to observe the Lagrangian near-surface and deep flow, and two Automatic Weather Stations to monitor surface weather conditions in the Marguerite
Bay-western Antarctic Peninsula shelf region. Supporting bathymetric, hydrographic (CTD/microstructure) and meteorological data were also collected to document the physical environment and surface forcing during the 2001-2003 field study. The drifter and moored measurements indicate a surface circulation consisting of an open regional clockwise gyre, with a wind- and buoyancy-driven coastal current that flows southward along Adelaide Island, into and around Marguerite Bay, and westward along the northern end of Alexander Island. Drifters exiting the Bay eventually move northeastward near the shelf break. The deeper currents tend to be barotropic, weakly bottom-intensified, and strongly influenced by local topography due to small subpynocline stratification. The moored current and hydrographic data suggest a mean flow of Lower Circumpolar Deep Water into Marguerite Bay along the northern flank of Marguerite Trough, thus making this deep canyon an important cross-shelf conduit for heat and salt. The strongest currents in all seasons are near-inertial oscillations, driven by both wind and sea ice motion. These are thought to be the primary source of vertical mixing.

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