Simulated formation of grounding-zone wedges and implications for ice-sheet stability

<p>Glacier flow has the potential to mobilize subglacial till, resulting in till deposition and subglacial landforms in glaciated areas. The subglacial till transport occurs when sedimentary beds are thawed and sufficiently weak relative to the glacial driving stress. As a consequence of till mobilization, soft-bedded and marine-terminating ice sheets are known to produce grounding-zone wedges. It has been hypothesized that these wedges may stabilize grounded ice in spite of rising sea level.</p><p>In order to test this hypothesis, we develop a fully coupled framework for simulating ice flow, glacier hydrology, and till advection. Ice flow and hydrology is handled with PISM, the three-dimensional, thermomechanical, parallel ice sheet model (Bueler and Brown, 2009; Winkelmann et al 2011). Till advection is computed with the cohesive non-granular fluidity method with pore-water pressure, which is consistent with Coulomb-frictional mechanics and stress-dependent shear-zone thickness (Damsgaard et al., 2020). We apply the model to various bed geometries and forcing scenarios, and show how subglacial landforms evolve and grounding-zone wedges form. The grounding-zone wedges prove to contribute conditional stabilization to the ice sheet, and this mechanism could limit the marine-ice sheet instabilities that may occur on reverse sloping beds.</p><p> </p><p>References:</p><p>Bueler, E. and Brown, J. 2009 “Shallow shelf approximation as a “sliding law” in a”. J. Geophys. Res. Earth Surf. 114(F3)</p><p>Damsgaard, A., L. Goren and J. Suckale 2020 “Water pressure fluctuations control variability in sediment flux and slip dynamics beneath glaciers and ice streams”. Commun. Earth Environ. 1(66), 1–8. doi: 10.1038/s43247-020-00074-7</p><p>Winkelmann, R., M. A. Martin, M. Haseloff, T. Albrecht, E. Bueler, C. Khroulev and A. Levermann 2011 “The Potsdam Parallel Ice Sheet Model (PISM-PIK) - Part 1: Model description”. 5(3), 715–726. doi: 10.5194/tc-5-715-2011</p>