Understanding the drivers of Kaskawulsh Glacier thinning, southwest Yukon, Canada, 2007-2018
Abstract
The Kaskawulsh Glacier is an iconic outlet draining the continental side of the icefields of the St. Elias Mountains in southwest Yukon, Canada. In 2016, its retreat prompted a spectacular hydrological reorganization in which its runoff was diverted to the Gulf of Alaska from its former route to the Bering Sea. We estimate the distributed catchment-wide mass balance of the Kaskawulsh Glacier. Here we use SPOT-5 and SPOT-6/-7 data to create digital elevation models of the Kaskawulsh Glacier in 2007 and 2018, respectively, from which we estimate the geodetic mass balance over this 11-year period. An average net glacier thinning of 0.56 +/- 0.08 m a-1 is observed where we have reliable data coverage corresponding to approximately two thirds of the glacier surface. To isolate the contributions of surface mass balance versus glacier dynamics to the observed spatial pattern of elevation change, we compare computed balance fluxes with estimated ice fluxes at six flux gates in the ablation zone. Glacier cross-sectional area at the flux gates is calculated from digital elevation models of the ice surface and bed topography determined from ice-penetrating radar surveys in 2018-2019. Downscaled bias-corrected values of air temperature and precipitation from the North American Regional Reanalysis (NARR) dataset are used to drive a mass-balance model assembled expressly for this study. An enhanced temperature-index model that incorporates potential direct solar radiation is used to estimate ablation, while accumulation is estimated from the downscaled precipitation using a fixed rain-to-snow threshold temperature. The remaining model parameters are tuned using in-situ measurements of summer-, winter- and net balance. With the model we estimate the 2007-2018 distributed surface mass balance, from which we compute the balance fluxes at the flux gates. Measured surface velocities and assumptions about glacier-flow partitioning between internal deformation and basal flow allow us to estimate actual ice fluxes at these locations. We then compare the ice thickness changes implied by the discrepancy between balance and estimated ice fluxes with the observed geodetic mass balance.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C31B1498Y
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0758 Remote sensing;
- CRYOSPHERE;
- 0762 Mass balance;
- CRYOSPHERE;
- 0776 Glaciology;
- CRYOSPHERE