Interaction between the Antarctic ice shelf regions and the ocean and its contribution to oceanic water mass formation:
Ice shelves represent the main areas of ice discharge from the Antarctic Ice Sheet into the Southern Ocean. At the transition between ice and ocean ice shelves affect both, the mass balance and dynamics of the ice sheet and the water mass formation in the Southern Ocean by ice shelf melting and calving at the shelf front, respectively.
Under constant boundary conditions (mass flux from the ice sheet, ice accumulation and melting) a balance between mass gain and mass loss occurs and the ice shelves, except for recurring calving events, establish an almost constant shape. In addition, ice shelves exert a buttressing force on the ice sheet and, therefore, are a regulating factor of ice discharge.
Under changing climatic conditions, manifested for example in a changed oceanic circulation and temperature, this equilibrium state might be disturbed. In a model study with a coupled ocean – ice shelf – ice sheet model, the influence of changing climate boundary conditions on the mass loss in the Atlantic sector of the Antarctic Ice Sheet, the water mass formation in the Weddell Sea and the sea level is investigated.
Starting form scenario runs of the Intergovernmental Panel on Climate Change (IPCC) Assessment Report IV (AR4), which describe the climate development to the year 2100, the dynamic coupling of ocean circulation and ice sheet dynamics predict a significant mass loss in the Filchner-Ronne Ice Shelf and in particular a retreat of its southern grounding line.
This predicted increase in mass loss is equivalent to a doubling of today’s observed losses and sets the previously assumed stability of the East Antarctic ice sheet to climate change into question.