Winter Sea Ice Properties in Marguerite Bay, Antarctica

D.K. Perovich, B.C. Elder, K.J. Claffey, S. Stammerjohn, R. Smith,

S.F. Ackley, H.R. Krouse, and A.J. Gow

During the winter 2001 and 2002 cruises of the South GLOBEC experiment, we sampled ice physical and optical properties in the Marguerite Bay area of the Western Antarctic Peninsula. At 18 floes, ice thickness was measured every meter along 10- to 120-m-long survey lines. The combined mean ice thickness for these surveys was 62 cm in 2001 and 102 cm in 2002, with medians of 43 cm and 68 cm, respectively. Snow depths averaged 16 cm in 2001 and 21 cm in 2002. At 40% of the thickness holes in 2001 and 17% in 2002, a combination of deep snow and thin ice resulted in negative freeboard and the potential for surface flooding. A stratigraphic analysis of ice thin sections showed that more than half of the ice sampled was granular and that virtually all of the upper 20 cm of the ice cover was granular. There were indications that snow-ice formation at the surface contributed significantly to ice formation. A δ¹⁸O analysis of ice cores taken in 2001 indicated that 15% of the samples had negative values, implying the presence of snow-ice. At most sites the base of the snow cover was wet and saline. The average ice salinity was 7 psu, with the largest salinities, of approximately 10 psu, found near the surface. The combination of warm ice temperatures and large salinities resulted in brine volumes that were typically greater than 5% and ice that was highly permeable. Autonomous buoys provided a temporal perspective on the sea ice mass balance and temperature.

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