71 Analysis of surface fluxes over inhomogeneous Antarctic sea-ice'

Monday, 9 July 2012
St. George (Westin Copley Place)
Rebecca A. Jansen, University of Leeds, Leeds, United Kingdom; and I. M. Brooks, J. C. King, T. A. Lachlan-Cope, and A. Weiss

The extent of the sea-ice region around Antarctica is large with a high level of seasonal variability. The surface fluxes over this large and dynamic region are poorly studied, due to the inaccessibility of the area and the high experimental cost of direct observations. Little is therefore known in detail about the surface fluxes over inhomogeneous Antarctic sea-ice or how changes to the sea-ice affect the surface fluxes. Aircraft observations over the sea-ice surrounding the Antarctic Peninsula, collected by the British Antarctic Survey, were used to calculate eddy-covariance fluxes of sensible heat and momentum and the neutral ten meter bulk drag coefficient (CDN10). Comparisons were made between observations at the Bellingshausen Sea, Weddell Sea and the Ronne Polynya. There are distinct differences in the general characteristics of the sea-ice between the locations, enabling an evaluation of the effect of different sea-ice conditions on the surface fluxes and CDN10. We found the mean CDN10 over the Ronne Polynya to be 0.0016 +/- 0.7 comparing well with previous studies over inhomogeneous 'polynya-like' surfaces. The mean CDN10 for the Bellingshausen Sea was found to be similar but with approximately twice the variability, while that for WS was extremely variable at 0.006 +/- 23.0. Comparisons between the surface fluxes over Weddell and Bellingshausen Sea showed little obvious difference and are comparable in magnitude and sign to previous observations over the Weddell Sea. As could be expected the sensible heat fluxes over the Ronne Polynya were markedly higher than the other locations, the momentum flux was also nearly double the values from the Weddell Sea. The observed sensible heat and momentum fluxes were also compared to values obtained using the Surface Heat Budget of the Arctic Ocean (SHEBA) bulk flux algorithm. In general, the SHEBA algorithm failed to recreate the variability seen in the observed fluxes at all locations. The algorithm was found to particularly struggle in low flux conditions, with the most dramatic disagreements seen between the lower momentum fluxes over the Weddell Sea.
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