SOS Antarctica - Slipping Or Shearing in the margins of outlet glaciers in Antarctica
applicants
Eberhard Karls Universität Tübingen
Fachbereich Geowissenschaften
Arbeitsgruppe Geologie und Geodynamik
project description
Most of the ice accumulated in the interior of Antarctica flows towards the ocean through a network of fast ice streams. At the ice-sheet boundary, ice streams come in contact with the ocean (i.e. at the grounding line) where floating ice shelves are formed. Here, ice is eventually attributed to the ocean through basal melting and the calving of icebergs. Ice shelves surround > 75% of the Antarctic coast and buttress the inflow of ice streams. This is because the fast moving ice shelves are decelerated by slow moving, partially regrounded ice at their margins. The resulting shear zone communicates stresses into the upstream direction stabilizing the tributary ice streams. Changes of the support strength are one of the few mechanisms that can explain rapid changes in ice discharge and, consequently, rapid changes in sea level rise. In this proposal, we investigate mechanisms that influence the development and support strength of shear margins. This includes their formation at the glacier outlets near the grounding line, their further development in the mid-ice shelf area. In particular, we hypothesize that the evolution of ice anisotropy is a dominant mechanism in shear-zone formation. If this holds true then microphysical processes acting on individual ice crystals have largescale effects, resulting in a weakening of the shear margins. It may also trigger coupled evolution of the ice-shelf morphology changing the sub-shelf ocean circulation. We test this hypothesis on the Nansen Ice Shelf with polarimetric ground penetrating radar and terrestrial radar interferometry (TRI). Results of this proposal are important because current ice sheet models are almost exclusively rely on an isotropic ice rheology. Consequently applied data assimilation techniques incorrectly attribute the effect of reduced ice shelf buttressing to other tuning parameters such as temperature or bulk viscosity, which directly leads to flawed projections of sea level rise.
DFG Programme Infrastructure Priority Programmes
term since 2022