Seasonal ice velocity changes of Greenlandic glaciers: insights from new and dense remote sensing observations and hydrological modeling
Abstract
Many Greenlandic glaciers show prominent changes in seasonal ice velocity potentially due to ice-ocean-atmosphere coupling and glacial internal factors. These factors include surface-melt induced changes in the subglacial hydrologic systems. Less is known about the role of subsurface hydrologic systems on ice motion which affect the seasonal speedup and slowdown with variable timing and magnitudes. Recently, Vijay et al., 2019 made use of Sentinel-1 SAR data to monitor the seasonal ice velocity changes of 45 Greenlandic glaciers and found a strong link between spring-autumn velocity variations and surface melting conditions for nearly half of the glaciers. This potentially highlights the role of seasonally evolving subglacial drainage channels. Here, we extend this work to 246 Greenlandic glaciers and distinguish two distinct seasonal velocity patterns close to the ice fronts of more than 100 glaciers. A fraction of glaciers speedup with the onset of surface melt, but slowdown during the second half of the melt season, after attaining mid-season maximum in speed. Other glaciers exhibit consistent speedup during autumn and winter, with no, or only a slight increase in speed with the melt onset. We also extend this analysis further inland and investigate discrepancies and similarities in velocity patterns at various distances from the ice front. This investigation is based on a robust and automatic statistical sequence applied over time-series ice velocities derived from Sentinel-1 data. We test the sensitivity of these glaciers to hydrologic rerouting by running a subglacial hydrologic routing model with stepwise increases in water pressure. Observations of spatially variable thinning, and the associated impact on effective pressures, are integrated into the hydrologic model from ASTER, SPOT-5, and ArcticDEM elevations combined with BedMachine3 bed topography.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C31B1503V
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0758 Remote sensing;
- CRYOSPHERE;
- 0762 Mass balance;
- CRYOSPHERE;
- 0776 Glaciology;
- CRYOSPHERE