Abstract
ABSTRACTWe have developed a two-dimensional coupled glacier–fjord model, which runs automatically using Elmer/Ice and MITgcm software packages, to investigate the magnitude of submarine melting along a vertical glacier front and its potential influence on glacier calving and front position changes. We apply this model to simulate the Hansbreen glacier–Hansbukta proglacial–fjord system, Southwestern Svalbard, during the summer of 2010. The limited size of this system allows us to resolve some of the small-scale processes occurring at the ice–ocean interface in the fjord model, using a 0.5 s time step and a 1 m grid resolution near the glacier front. We use a rich set of field data spanning the period April–August 2010 to constrain, calibrate and validate the model. We adjust circulation patterns in the fjord by tuning subglacial discharge inputs that best match observed temperature while maintaining a compromise with observed salinity, suggesting a convectively driven circulation in Hansbukta. The results of our model simulations suggest that both submarine melting and crevasse hydrofracturing exert important controls on seasonal frontal ablation, with submarine melting alone not being sufficient for reproducing the observed patterns of seasonal retreat. Both submarine melt and calving rates accumulated along the entire simulation period are of the same order of magnitude, ~100 m. The model results also indicate that changes in submarine melting lag meltwater production by 4–5 weeks, which suggests that it may take up to a month for meltwater to traverse the englacial and subglacial drainage network.
Highlights
At the time of the last IPCC report, the projected contributions to global mean sea-level rise (SLR) to the end of the 21st century by mass losses from glaciers and ice caps were between 40 and 230 mm, depending on emission pathway
Our usg velocities for a 2-D model were considerably lower than those used by Xu and others (2012) for Store glacier. This could be due to the different size of the modeled systems, since surface meltwater (SMW) fluxes in our system is over ten times lower than that estimated for Store glacier (9 vs 100 m3s−1)
We focused on the effect of subglacial fresh water discharge on fjord properties and submarine melting (SMR), and the effects of SMR and CWD on calving and glacier front position changes
Summary
At the time of the last IPCC report, the projected contributions to global mean sea-level rise (SLR) to the end of the 21st century by mass losses from glaciers and ice caps (glaciers) were between 40 and 230 mm, depending on emission pathway. More recent model projections of glacier contribution to SLR to the end of the 21st century range between 79 and 157 mm and suggest that losses by frontal ablation of tidewater glaciers (iceberg calving plus subaerial and submarine melting at the near-vertical calving front) may be important contributors for regions such as peripheral Antarctica, Svalbard and the Russian Arctic (Huss and Hock, 2015) The significance of this contribution is supported by the high sensitivity of tidewater glaciers to ocean forcing (Rignot and others, 2010; Motyka and others, 2013; Straneo and Heimbach, 2013; Luckman and others, 2015). Subglacial fresh water inputs mainly come from surface meltwater (SMW)
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