Preprints
https://doi.org/10.5194/tc-2021-338
https://doi.org/10.5194/tc-2021-338

  24 Nov 2021

24 Nov 2021

Review status: this preprint is currently under review for the journal TC.

Persistent, Extensive Channelized Drainage Modeled Beneath Thwaites Glacier, West Antarctica

Alexander O. Hager1,2, Matthew J. Hoffman2, Stephen F. Price2, and Dustin M. Schroeder3,4 Alexander O. Hager et al.
  • 1Department of Earth Sciences, University of Oregon, Eugene, OR, USA
  • 2Fluid Dynamics and Solid Mechanics Group, Los Alamos National Laboratory, Los Alamos, NM, USA
  • 3Department of Electrical Engineering, Stanford University, Stanford, CA, USA
  • 4Department of Geophysics, Stanford University, Stanford, CA, USA

Abstract. Subglacial hydrology is a leading control on basal friction and the dynamics of glaciers and ice sheets. At low discharge, subglacial water flows through high-pressure, sheet-like systems that lead to low effective pressures. However, at high discharge, subglacial water melts the overlying ice into localized channels that efficiently remove water from the bed, thereby increasing effective pressure and basal friction. Recent observations suggest channelized subglacial flow exists beneath Thwaites Glacier, yet it remains unclear if stable channelization is feasible in West Antarctica, where surface melting is nonexistent and water at the bed is limited. Here, we use the MPAS-Albany Land Ice model to run a suite of over 130 subglacial hydrology simulations of Thwaites Glacier across a wide range of physical parameter choices to assess the likelihood of channelization. We then narrow our range of viable simulations by comparing modeled water thicknesses to previously observed radar specularity content, which indicates flat, spatially extensive water bodies at the bed. In all of our data-compatible simulations, stable channels reliably form within 100–200 km of the grounding line, and reach individual discharge rates of 35–110 m3 s−1 at the ice-ocean boundary. While only one to two channels typically form across the 200 km width of the glacier in our simulations, their high efficiency drains water across the entire lateral extent of the glacier. No simulations resembled observed specularity content when channelization is disabled. Our results suggest channelized subglacial hydrology has two consequences for Thwaites Glacier dynamics: (i) amplifying submarine melting of the terminus and ice shelf, while (ii) simultaneously raising effective pressure within 100 km of the grounding line and increasing basal friction. The distribution of effective pressure implied from our modeling differs from parameterizations typically used in large-scale ice sheet models, suggesting the development of more process-based parameterizations may be necessary.

Alexander O. Hager et al.

Status: open (until 19 Jan 2022)

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Alexander O. Hager et al.

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Persisent, Extensive Channelized Drainage Modeled Beneath Thwaites Glacier, West Antarctica Hager, Alexander O., Hoffman, Matthew J., Price, Stephen F., Schroeder, Dustin M. https://doi.org/10.5281/zenodo.5593376

Alexander O. Hager et al.

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Short summary
The presence of water beneath glaciers is a control on glacier speed and ocean-caused melting, yet it has been unclear whether sizeable volumes of water can exist beneath Antarctic glaciers, or how this water may flow along the glacier bed. We use computer simulations, supported by observations, to show that enough water exists at the base of Thwaites Glacier, Antarctica, to form "rivers" beneath the glacier. These rivers likely moderate glacier speed and may influence its rate of retreat.