Large scale impacts of surface melt on ice sheet dynamics: Empirical evidence of outlet glacier sensitivity to late-season melt events in Greenland
Abstract
Many Greenland outlet glaciers exhibit a marked seasonal acceleration near-coincidentally with the onset of surface melt. The key mechanisms of this seasonal velocity signal have been well documented as a response to evolving subglacial drainage efficiency, where an initial acceleration due to increased basal water pressures is followed by deceleration once the formation of efficient channelized networks reduce pressures. Less is understood, however, on how surface melt drives variability in the timing and magnitude of acceleration and deceleration, and consequently how melt impacts large-scale, mean glacier velocities and dynamic ice loss from the ice sheet. Here, we conduct an ice sheet-wide study comparing the seasonal distribution of melt events, taken from the latest modeled RACMO runoff product, with decadal records of glacier velocities derived from Landsat 7 and 8, TerraSAR-X, and Sentinel-1 for all large outlet glaciers in Greenland. We find evidence that glacier velocities during the deceleration phase are sensitive to the timing and distribution of melt events, and that deceleration occurs less rapidly in years with intermittent meltwater pulses. These results suggest that the distribution of melt and runoff, rather than a seasonal sum, is more important to Greenland glacier dynamics. Additionally, we interpret these results to suggest that subglacial drainage system efficiency may be transient even following channelization, and thus glacier flow is sensitive to late season melt events. Lastly, we describe where on the ice sheet this relationship is strongest and evaluate the net impact of deceleration-phase variability on mean glacier speeds and ice sheet discharge.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C12A..02K
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0726 Ice sheets;
- CRYOSPHERE;
- 0730 Ice streams;
- CRYOSPHERE;
- 0776 Glaciology;
- CRYOSPHERE