Dynamics of ice shelves and their sensitivity to changing mass-balance quantities Model results for Filchner-Ronne ice shelf, Antarctica,

Previous evidence suggests basal layer up to 400 m thick. Attempts to demonstrate that this consists of marine ice which grew in water column beneath ice shelf. Application of finite-differences ice-flow model reveals contribution of bottom melting and accumulation to mass budget. Basal interactions also control steady-state thickness profile of ice shelf. In answering the relevant question for the mass budget of the antarctic ice sheet, the ice shelves fringing the continent play an important role because they largely drain the ice flowing from inland. Using the flow law for ice, a set of differential equations describes ice-shelf flow in the horizontal dimensions. By reproducing the observed flow of the Filchner-Ronne Ice Shelf, the model is used to simulate transient ice-shelf dynamics. This implies solving the equation of mass conservation, involving accumulation rates and ablation rates from the ice-shelf surface and bottom. While glaciological field studies presently represent surface accumulation rates fairly well, there is still little access to bottom melting which seems to be one order higher in magnitude. For the central region of Filchner-Ronne Ice Shelf, rates of basal accumulation in excess of 2 m/y can be derived inversely by maintaining a basal layer of marine ice in its present extent. Analysis of an ice core sampling on Filchner-Ronne Ice Shelf about 30 km inland from the ice front reveals that this basal layer consists of ice which probably grew in the water column beneath the ice shelf. Prognostic studies comprising hypothetical distributions of accumulation and melting reveal that the ice-shelf thickness profile strongly depends on interactions with the ocean. Mass budget estimates suggest that melting at the ice-shelf bottom discharges at least as much ice as does calving at the ice front