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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2018-28
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Model description paper
13 Mar 2018
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Geoscientific Model Development (GMD).
A continuum model of ice mélange and its role during retreat of the Antarctic Ice Sheet
David Pollard1, Robert M. DeConto2, and Richard B. Alley1,3 1Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802, USA
2Department of Geosciences, University of Massachusetts, Amherst, MA 01003, USA
3Department of Geosciences, Pennsylvania State University, University Park, PA 16802, USA
Abstract. Rapidly retreating thick ice fronts can generate large amounts of mélange (floating ice debris), which may affect episodes of rapid retreat of Antarctic marine ice. In modern Greenland fjords, mélange provides substantial back pressure on calving ice faces, which slows ice-front velocities and calving rates. On the much larger scales of West Antarctica, it is unknown if mélange could clog seaways and provide enough back pressure to act as a negative feedback slowing retreat. Here we describe a new mélange model, using a continuum mechanical formulation that is computationally feasible for long-term continental Antarctic applications. It is tested in an idealized rectangular channel, and calibrated very basically using observed modern conditions in Jakobshavn fjord, West Greenland. The model is then applied to drastic retreat of Antarctic ice in response to warm mid-Pliocene climate. With mélange parameter values that yield reasonable modern Jakobshavn results, Antarctic marine ice still retreats drastically in the Pliocene simulations, with little slowdown despite the huge amounts of mélange generated. This holds both for the rapid early collapse of West Antarctica, and later retreat into major East Antarctic basins. If parameter values are changed to make the mélange much more resistive to flow, far outside the range for reasonable Jakobshavn results, West Antarctica still collapses and retreat is slowed or prevented only in a few East Antarctic basins.
Citation: Pollard, D., DeConto, R. M., and Alley, R. B.: A continuum model of ice mélange and its role during retreat of the Antarctic Ice Sheet, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2018-28, in review, 2018.
David Pollard et al.
David Pollard et al.
David Pollard et al.

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Short summary
Around the margins of ice sheets in contact with the ocean, breaking of icebergs can generate large amounts of floating ice debris called "melange". In major Greenland fjords, melange significantly slows down ice flow from upstream. Our study uses numerical models applied to past and possible future episodes of drastic Antarctic Ice Sheet retreat. We find that, unlike Greenland, the Antarctic melange does not significantly impede flow or slow ice retreat and associated sea-level rise.
Around the margins of ice sheets in contact with the ocean, breaking of icebergs can generate...
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