The Sea Ice Thickness in the Atlantic Sector of the Southern Ocean

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Sea-ice covers large regions of the World Ocean. As it blankets millions of square kilometers, it significantly regulates the surface fluxes of water, heat and momentum between the ocean and the atmosphere. Thus, it has a profound influence on the regional climate and the polar physical environment in both hemispheres. It also plays a major role in the global climate system, due to its ability of reflecting sunlight or its influence on the freshwater budget of the polar oceans. Examining the changes of sea-ice has thus become an important field in Earth System Science. With the rapid decline of Arctic sea-ice, also the Antarctic sea-ice cover has attracted more scientific interest. Contrary to the sea-ice extent and concentration, the thickness of sea-ice is not routinely measured from space with sufficient accuracy. Moreover, submarine sonar measurements of ice thickness are not available for the Antarctic. The only way of monitoring the long-term variations of the sea-ice thickness in the Southern Ocean are moored upward looking sonars (ULSs). Since 1990 the Alfred Wegener Institute (AWI) maintains an array of 13 ULSs in the Atlantic sector of the Southern Ocean. This project is focussed on the analysis of ULS-data in terms of sea-ice thickness variations and possible long-term trends. It is planned to find possible correlations between the sea-ice thickness derived from ULS measurements and other oceanic and atmospheric properties (e.g. the Southern Annular Mode) to identify the forcing mechanisms of sea-ice thickness changes. Another goal of this project is to set up a consistent dataset of ULS draft measurements which can be used to validate satellite-derived ice thickness estimates and sea-ice models.