A simple model of mélange buttressing for calving glaciers

Abstract

Abstract. Both ice sheets on Greenland and Antarctica are discharging ice into the ocean. In many regions along the coast of the ice sheets, the icebergs calf 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 but robust buttressing model of ice mélange which can be used in numerical and analytical modeling.

The triggers of the disaggregation of Voyeykov Ice Shelf (2007), Wilkes Land, East Antarctica, and its subsequent evolution

“…8). This behaviour is similar to other ice shelves and outlet glaciers terminating in tightly-packed mélange in Antarctica and Greenland, which has been shown to inhibit calving events and prevent the detachment of icebergs (Higgins, 1991; Reeh and others, 2001; Amundson and others, 2010; Moon and others, 2015; Hill and others, 2017; Robel, 2017; Burton and others, 2018; Schlemm and Levermann, 2020). For example, the continuous presence of mélange bound by MYLI has stabilised Cook West Ice Shelf in East Antarctica and enabled it to slowly advance following its near-complete loss between 1973 and 1989 (Miles and others, 2018).…”

“…The significant decrease in ice flow velocities between 2007 and 2009 on the distal portion of VIS (Fig. 5) implies the buttressing provided by the disaggregated portion of VIS and mélange was low (Fürst and others, 2016; Miles and others 2020; Schlemm and Levermann, 2020). Comparing the spatial pattern in velocity differences before and after the disaggregation event, we record a band of flow acceleration (up to 115 m a −1 ) along the WSZ between 2007 and 2008 (Figs 5e, f).…”

“…The frequency of major calving events and large-scale retreat can be modulated by ice mélange (an amalgamation of sea ice, marine ice, firn and densely packed calved icebergs), which is known to exert a buttressing force on floating glacier tongues and ice shelves (Amundson and others, 2010; Massom and others, 2010; Carr and others, 2013; Moon and others, 2015; Burton and others, 2018; Xie and others, 2019; Schlemm and Levermann, 2020). Because of this, the removal of ice mélange and the associated reduction in buttressing can weaken the structural integrity of floating glacier tongues and ice shelves (Cassotto and others, 2015; King and others, 2018; Miles and others, 2020).…”