Abstract
Abstract. Both ice sheets in Greenland and Antarctica are discharging ice into the ocean. In many regions along the coast of the ice sheets, the icebergs calve into a bay. If the addition of icebergs through calving is faster than their transport out of the embayment, the icebergs will be frozen into a mélange with surrounding sea ice in winter. In this case, the buttressing effect of the ice mélange can be considerably stronger than any buttressing by mere sea ice would be. This in turn stabilizes the glacier terminus and leads to a reduction in calving rates. Here we propose a simple parametrization of ice mélange buttressing which leads to an upper bound on calving rates and can be used in numerical and analytical modelling.
Highlights
Ice sheets gain mass by snowfall and freezing of seawater and lose mass through calving of icebergs and melting at the surface and the bed
We propose that ice mélange, a mix of icebergs and sea ice that is found in many glacial embayments, gives rise to a negative feedback on calving rates
Backed by evidence for mélange buttressing in observations and numerical simulations, we propose that mélange buttressing may be one mechanism that prevents calving rates from growing too large
Summary
Ice sheets gain mass by snowfall and freezing of seawater and lose mass through calving of icebergs and melting at the surface and the bed. This study provides a simple parametrization that accounts for the buttressing effect of ice mélange on calving on a large spatial scale and that can be used for continentalscale ice sheet modelling. Observations in Store Glacier and Jakobshavn Glacier in Greenland have shown that in the winter, when sea ice is thick, ice mélange prevents calving (Walter et al, 2012; Xie et al, 2019) This has been reproduced in modelling studies of grounded marine glaciers (Krug et al, 2015; Todd et al, 2018, 2019): back stresses from the mélange reduce the stresses in the glacier terminus, thereby limit-. Application to two calving parametrizations and possible simplifications are discussed in Sect. 4, and in Sect. 5 the mélange-buttressed calving rates are applied in an idealized glacier set-up
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