Abstract
AbstractWe calibrate the calving parameterisation implemented in the Open Global Glacier Model via two methods (velocity constraint and surface mass balance (SMB) constraint) and assess the impact of accounting for frontal ablation on the ice volume estimate of Greenland tidewater peripheral glaciers (PGs). We estimate an average regional frontal ablation flux of 7.38±3.45 Gta−1 after calibrating the model with two different satellite velocity products, and of 0.69±0.49 Gta−1 if the model is constrained using frontal ablation fluxes derived from independent modelled SMB averaged over an equilibrium reference period (1961–90). This second method makes the assumption that most PGs during that time have an equilibrium between mass gain via SMB and mass loss via frontal ablation. This assumption serves as a basis to assess the order of magnitude of dynamic mass loss of glaciers when compared to the SMB imbalance. The differences between results from both methods indicate how strong the dynamic imbalance might have been for PGs during that reference period. Including frontal ablation increases the estimated regional ice volume of PGs, from 14.47 to 14.64±0.12 mm sea level equivalent when using the SMB method and to 15.84±0.32 mm sea level equivalent when using the velocity method.
Highlights
At its rapidly warming margins (Shepherd and others, 2020), the Greenland ice sheet (GrIS) is surrounded by detached glaciated areas, commonly referred to in the literature as peripheral glaciers (PGs) and ice caps (Rastner and others, 2012; Bjørk and others, 2018)
Regional volumes are underestimated by 12% if frontal ablation is ignored and/or if the model only relies on surface mass balance (SMB) estimates and the assumption of a closed budget to calibrate the calving parameterisation
If we remove the ice cap from our analysis, we find that the consensus glacier volumes for the remaining glaciers are underestimated by 4% when compared to Open Global Glacier Model (OGGM) results that account for a frontal ablation and use the RACMO calibration method and up to 12% when compared to OGGM results using the velocity method to constrain the frontal ablation parameterisation
Summary
At its rapidly warming margins (Shepherd and others, 2020), the Greenland ice sheet (GrIS) is surrounded by (semi-) detached glaciated areas, commonly referred to in the literature as peripheral glaciers (PGs) and ice caps (Rastner and others, 2012; Bjørk and others, 2018). According to Bolch and others (2013), all glaciers and ice caps (including those with strong but hydrologically separable connections) lost 40.9±16.5 Gta−1 (0.12±0.05 mm SLE) between 2003 and 2008 This is a significant fraction (up to 14 or 20%) of the reported overall mass loss of Greenland and up to 10% of the estimated contribution from the world’s glaciers and ice caps to sea-level rise (Bolch and others, 2013). In a scenario of continued global warming, Greenland’s PGs may lose 19–28% (7.5–11 mm) of their volume by 2100 (Machguth and others, 2013)
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