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Impact of ice-shelf basal melting on inland ice-sheet thickness: a model study

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Determann, J. , Thoma, M. , Grosfeld, K. and Maßmann, S. (2012): Impact of ice-shelf basal melting on inland ice-sheet thickness: a model study , Annals of Glaciology, 53 (60), pp. 129-135 . doi: 10.3189/2012AoG60A170
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Abstract:

Ice flow from the ice sheets to the ocean contains the maximum potential contributing to future eustatic sea level rise. In Antarctica most of the mass fluxes occur via the extended ice shelf regions, covering more than one half of the Antarctic coast line. The most extended ice shelves are the Filchner-Ronne and Ross ice shelves, contributing about 30% to the total mass loss caused by basal melting. Basal melt rates show here small to moderate amplitudes of lower than 0.5 m/a on average. In comparison, the smaller but most vulnerable ice shelves in the Amundsen and Bellingshausen Seas show much higher melt rates (up to 30 ma-1) but overall basal mass loss is comparably small due to the small size of the ice shelves. The pivotal question for both characteristic ice shelf regions, however, is the impact of ocean melting and coevally change in ice-shelf thickness on the flow dynamics of the hinterland ice masses. In theory, ice-shelf back-pressure acts to stabilize the ice sheet, and thus the ice volume stored above sea level. We use the three-dimensional thermomechanical ice flow model RIMBAY to investigate the ice flow in a regularly shaped model domain, including ice sheet, ice shelf, and open-ocean regions. By using melting scenarios for perturbation studies, we find a hysteresis-like behaviour. The experiments show that the system reattains initial state when perturbations are switched off. Average basal melt rates of up to 2 ma-1 as well as spatially variable melting calculated by our 3d ocean model ROMBAX act as basal boundary conditions in time-dependent model studies. Changes in ice volume and grounding-line position are monitored after 1000 years of modelling and reveal mass losses of up to 40 Gta-1.

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