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[1] The radiative and turbulent heat fluxes between the snow-covered sea ice and the atmosphere were analyzed on the basis of observations during the Ice Station Polarstern (ISPOL) in the western Weddell Sea from 28 November 2004 to 2 January 2005. The net heat flux to the snowpack was 3 ± 2 W m À2 (mean ± standard deviation; defined positive toward snow), consisting of the net shortwave radiation (52 ± 8 W m À2 ), net longwave radiation (À29 ± 4 W m À2 ), latent heat flux (À14 ± 5 W m À2 ), and sensible heat flux (À6 ± 5 W m À2 ). The snowpack receives heat at daytime while releases heat every night. Snow thinning was due to approximately equal contributions of the increase of snow density, melt, and evaporation. The surface albedo only decreased from 0.9 to 0.8. During a case of cold air advection, the sensible heat flux was even below À50 W m À2 . At night, the snow surface temperature was strongly controlled by the incoming longwave radiation. The diurnal cycle in the downward solar radiation drove diurnal cycles in 14 other variables. Comparisons against observations from the Arctic sea ice in summer indicated that at ISPOL the air was colder, surface albedo was higher, and a larger portion of the absorbed solar radiation was returned to the atmosphere via turbulent heat fluxes. The limited melt allowed larger diurnal cycles. Due to regional differences in atmospheric circulation and ice conditions, the ISPOL results cannot be fully generalized for the entire Antarctic sea ice zone.

Sea-ice drift and deformation in the western Weddell Sea in early austral summer of 2004 are characterised using in situ data from a meso-scale array of 24 drifting ice buoys. Horizontal GPS-derived position measurements are available from drifting buoys deployed as part of the Ice Station POLarstern [ISPOL] experiment for 26 days during late November and December 2004, at various temporal resolutions and spatial accuracies. These data form the basis for sea-ice velocity and deformation measurements across the meso-scale ISPOL array and at two remote sites. Analysis of the sea-ice velocities reveals coherence for sea-ice drift at separations of less than 70 km; and a correlation length scale of 60 km. Within the limits of the ISPOL array, at larger separations zonal ice drift remains correlated, while meridional ice drift becomes uncorrelated. This together with the east-west gradient in ice velocities indicates the influence of bathymetry, via tidal forcing, on local dynamic processes. Atmospheric forcing also contributes to the sea-ice drift: about 40% of variability in the sea-ice velocity is explained by changes in wind velocity, which is significantly less than other studies have found for the region during winter. Sea-ice deformation has been derived for the overall array and four sub-arrays. There appeared to be no spatial scale dependency of ice deformation, although considerable spatial variability was observed between sub-arrays. The net divergence of the ISPOL array was in excess of 30%, with the largest contributions to divergence being from the southern section and along the eastern side of the overall ISPOL array. Temporal variability for all deformation parameters is dominated by high-frequency (sub-daily) processes, namely tidal forcing and inertial response. Low-frequency (multiple days) processes, including atmospheric changes, played a secondary role in forcing sea-ice deformation during ISPOL. r