Circulation patterns on
the western Antarctic Peninsula shelf during 2001-2003
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.
Title, abstract, and author list received on 06/23/05.