Controls on calving at a large Greenland tidewater glacier: stress regime, self-organised criticality and the crevasse-depth calving law

• Published in: Journal of Glaciology
• Main Authors: Benn, Douglas I., Todd, Joe, Luckman, Adrian, Bevan, Suzanne, Chudley, Thomas R., Åström, Jan, Zwinger, Thomas, Cook, Samuel, Christoffersen, Poul
• Other Authors: NERC Environmental Bioinformatics Centre, Natural Environment Research Council, Horizon 2020 Framework Programme
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2023
• Subjects: glacier; Greenland; Journal of Glaciology; Kujalleq; Sermeq Kujalleq; Tidewater
• Online Access: http://dx.doi.org/10.1017/jog.2023.81; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143023000813

Abstract We investigate the physical basis of the crevasse-depth (CD) calving law by analysing relationships between glaciological stresses and calving behaviour at Sermeq Kujalleq (Store Glacier), Greenland. Our observations and model simulations show that the glacier has a stable position defined by a compressive arch between lateral pinning points. Ice advance beyond the arch results in calving back to the stable position; conversely, if melt-undercutting forces the ice front behind the stable position, it readvances because ice velocities exceed subaqueous melt rates. This behaviour is typical of self-organising criticality, in which the stable ice-front position acts as an attractor between unstable super-critical and sub-critical regimes. This perspective provides strong support for a ‘position-law’ approach to modelling calving at Sermeq Kujalleq, because any calving ‘rate’ is simply a by-product of how quickly ice is delivered to the critical point. The CD calving law predicts ice-front position from the penetration of surface and basal crevasse fields, and accurately simulates super-critical calving back to the compressive arch and melt-driven calving into the sub-critical zone. The CD calving law reflects the glaciological controls on calving at Sermeq Kujalleq and exhibits considerable skill in simulating its mean position and seasonal fluctuations.