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Calving Multiplier Effect Controlled by Melt Undercut Geometry

2021; Wiley; Volume: 126; Issue: 7 Linguagem: Inglês

10.1029/2021jf006191

2169-9011

Donald Slater, Douglas I. Benn, Tom Cowton, J. N. Bassis, Joe Todd,

Arctic and Antarctic ice dynamics

Abstract Quantifying the impact of submarine melting on calving is central to understanding the response of marine‐terminating glaciers to ocean forcing. Modeling and observational studies suggest the potential for submarine melting to amplify calving (the calving multiplier effect), but there is little consensus as to under what conditions this occurs. Here, by viewing a marine‐terminating glacier as an elastic beam, we propose an analytical basis for understanding the presence or absence of the calving multiplier effect. We show that as a terminus becomes undercut it becomes more susceptible to both serac failure (calving only of ice that is undercut, driven by vertical imbalance) and rotational failure (full‐thickness calving of ice behind the grounding line, driven by rotational imbalance). By deriving analytical stress thresholds for these two forms of calving, we suggest that the dominant of the two calving styles is determined principally by the shape of melt‐undercutting. Uniform undercutting extending from the bed to the waterline promotes serac failure and no multiplier effect, while glaciers experiencing linear undercutting that is greatest at the bed and zero at the waterline are more likely to experience rotational failure and a multiplier effect. Our study offers a quantitative framework for understanding where and when the calving multiplier effect occurs, and, therefore, a route to parameterizing the effect in ice sheet‐scale models.