Sea ice growth in the eastern Weddell Sea in winter

Abstract

The energy budget and the formation of sea ice in the eastern Weddell Sea west of Maud Rise are investigated on a regional scale on the basis of data obtained from drifting buoys deployed during the ANZFLUX project in 1994. A one-dimensional model for snow-covered sea ice and a kinematic-thermodynamic sea ice model for ice formed in leads are coupled and run under atmospheric and oceanic conditions specified from in situ data. Flooding at the snow-ice interface and snow ice formation need to be accounted for to achieve reasonable agreement between modeled and measured temperature distributions. The time-averaged values for the net heat flux are 21 W m-2, some 60% of which originate in refreezing leads, and 9.8 cm for the monthly rate of ice accumulation. Whereas leads contribute a net accumulation of 10.8 cm, the mass balance of consolidated, snow-covered ice results in a net ablation of - 1.0 cm. Sensitivity studies reveal the contribution of processes related to snow cover and ocean heat flux to sea ice formation and heat exchange. Without taking snow ice formation into account, a net ablation of - 14.9 cm occurs under snow-covered ice due to high oceanic heat fluxes. A comparison between a simple two-layer model and the one-dimensional thermodynamic model emphasizes the influence of heat storage in sea ice on the development of heat flux and ice thickness. The heat and mass fluxes obtained on a regional scale, and their sensitivity to the parameterizations, elucidate the implication of vigorous small-scale processes on sea ice development and point out their importance for sea ice models.