ON THE OCEANS UPPER BOUNDARY-CONDITIONS IN REGIONS INFLUENCED BY SEA-ICE

During recent years, studies with global ocean general circulation mod els (OGCMs) revealed strong dependencies of their performance on the w ay the impact of the atmosphere is prescribed, specifically how vigoro usly the upper ocean is tied to lower atmosphere conditions. The prese nce of sea ice introduces further complication to this prescription, d ue to its dynamic and thermodynamic characteristics, and due to its se nsitive dependency on the ambient atmospheric and oceanic conditions. This study provides an overview over the highly nonlinear and interact ive processes involved with sea ice modifying the upper boundary condi tions for ocean models in polar regions, We address the physical repre sentation of sea ice in present-day global OGCMs in comparison to regi onal state-of-the-art sea-ice models. We discuss the role of different external forcing fields, and various sea-ice forcing mechanisms consi dering the role of interactive boundary-layer processes. This discussi on includes the nonlinear impact of subgrid-scale heterogeneities on t he momentum forcing. Finally, the possible impact of sea ice on global ocean characteristics is discussed.