Abstract
At many marine-terminating glaciers, the breakup of mélange, a floating aggregation of sea ice and icebergs, has been accompanied by an increase in iceberg calving and ice mass loss. Previous studies have argued that mélange may suppress calving by exerting a buttressing force directly on the glacier terminus. In this study, I adapt a discrete element model to explicitly simulate mélange as a cohesive granular material. Simulations show that mélange laden with thick landfast sea ice produces enough resistance to shut down calving at the terminus. When sea ice within mélange thins, the buttressing force on the terminus is reduced and calving is more likely to occur. When a calving event does occur, it initiates a propagating jamming wave within mélange, which causes local compression and then slow mélange expansion. The jamming wave can also initiate widespread fracture of sea ice and further increase the likelihood of subsequent calving events.
Highlights
At many marine-terminating glaciers, the breakup of melange, a floating aggregation of sea ice and icebergs, has been accompanied by an increase in iceberg calving and ice mass loss
Projections of the future ice sheet contribution to sea level rise can vary by several metres depending on the rate of iceberg calving at ice sheet margins[1,2,3]
The recent increase in the rate of iceberg calving and associated mass loss at many marineterminating glaciers in Greenland and Antarctica has been accompanied by rapid breakup of iceberg melange, a dense aggregation of icebergs and sea ice floating in front of glacier termini[4,5,6]
Summary
At many marine-terminating glaciers, the breakup of melange, a floating aggregation of sea ice and icebergs, has been accompanied by an increase in iceberg calving and ice mass loss. The parameterizations associated with these model simplifications are not well constrained by the limited set of melange observations that exist, but the results discussed in this study are not sensitively dependent on these parameter choices (Table 1) Using this new approach to modelling melange, I show that when bonded by a matrix of thick landfast sea ice, melange is capable of exerting sufficient buttressing force on the glacier terminus to shut down calving. When a calving event does occur, it initiates a propagating jamming wave within the melange, which can cause fracture of the sea-ice matrix Such large-scale sea ice fracture within melange decreases the buttressing force of melange on the glacier terminus and further increases the likelihood of subsequent calving events
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