Parizek Abstract

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Dynamic (In)stability of Thwaites Glacier, West Antarctica

B. R. Parizek, K. Christianson, S. Anandakrishnan, R. B. Alley, R. T. Walker, R. A. Edwards, D. S. Wolfe, G. T. Bertini, S. K. Rinehart, R. A. Bindschadler, and S. M. J. Nowicki

Thwaites Glacier, West Antarctica has the potential to directly contribute 1 m to sea level, and currently is losing mass and thinning rapidly. Here we report on regional results for the Sea-level Response to Ice Sheet Evolution (SeaRISE) experiments and investigate the impact of i) spatial resolution within existing data sets, ii) grounding-zone processes, and iii) till rheology on the dynamics of this outlet glacier. In addition to the SeaRISE datasets, we use detailed aerogeophysical and satellite data from Thwaites Glacier as input to a coupled ice-stream/ice-shelf/ocean-plume model that includes oceanic influences across a several-kilometers-wide grounding zone suggested by new, high resolution data. Our results indicate that the ice tongue provides limited stability, that while future atmospheric warming will likely add mass to the surface of the glacier, ice-stream stabilization on bedrock highs narrower than the width of the grounding zone may be ephemeral, and that Thwaites Glacier has the potential to retreat several hundred kilometers in a few decades. Furthermore, although initial stability is enhanced by weaker till beds, so are subsequent retreat rates. Thus, accurate projections of future sea-level change will require both improved grounding-zone data and important revisions to ice-sheet models, which now consider ice-sheet grounding to occur at a single point along flow (or grid-scale line across flow).