Characterization of sea ice cover, motion and dynamics in Marguerite Bay, Antarctic Peninsula

J. Hyatt^#, R.C. Beardsley^#, and W.B. Owens^#

^#Woods Hole Oceanographic Institution, Department of Physical Oceanography, Woods Hole, MA 02543 jhyatt@whoi.edu

Two years of moored oceanographic and automatic weather station data which span the winter ice seasons of 2001-2003 are used to detect the onset, thickness and motion of sea ice within Marguerite Bay on the western Antarctic Peninsula shelf as part of the U.S. GLOBEC Southern Ocean Program. The subsurface moorings were deployed in the ice-free austral summer and observed the onset and breakup of sea ice. They had upward-looking ADCPs to measure currents, ice presence, draft and motion, along with measurements of temperature, salinity, pressure and velocity at various depths. Both years have roughly seven months of nearly complete ice cover, but the onset of ice formation is about two months earlier in 2002-2003 than in the prior year due to one of the coldest May/June periods on record since 1976. The ice draft is considerable, over 3 m lasting for weeks during both observed winters. A linear momentum balance shows the importance of internal ice stresses in explaining the observed motion of the ice pack which is consistent with the high observed ice concentrations and drafts, and the semi-enclosed nature of Marguerite Bay. Tidal motions are weak, and most of the kinetic energy is in the near-inertial band.