Role of melt forcing in diurnal velocity fluctuations of Helheim Glacier, East Greenland
Abstract
High-resolution, in situ measurements of near-terminus Greenland tidewater glacier flow record the complex interaction between the ice sheet, ocean, and atmosphere on hourly to seasonal timescales. Atmospheric forcing drives variations in meltwater input to the ice-bed interface. The ocean boundary affects the glacier response to meltwater input through controls on subglacial water storage and discharge in the near-terminus region. Here we investigate how atmospheric and oceanic forcing influence short-term variations in horizontal flow of Helheim Glacier, East Greenland, as observed over the 2007 melt season by an array of high-resolution Global Positioning System (GPS) receivers that span a distance of 2-25 km from the calving front. Using a stochastic-filter approach (Davis et al., 2014), we estimate a diurnal component of horizontal glacier flow that modifies the background flow velocity, together with a principally semi-diurnal ocean-tide response. While tidally forced semi-diurnal variations in flow are observed to 10 km inland of the terminus, diurnal variations in flow are observed at least 20 km inland. The amplitude of diurnal variations generally decreases inland from the terminus and shows multi-day temporal variability. The daily speed maximum of diurnal variations occurs a few hours after the late-afternoon peak daily temperatures recorded at the permanent weather station in Tasiilaq, 100 km from the glacier. Our observations suggest that daily melt magnitude and timing exert some influence on outlet glacier velocity, likely through the modification of resistance to flow at the ice-bed interface. We hypothesize that marine-terminating glacier systems in Greenland exhibit melt-response behavior akin to land-terminating and mountain glaciers, perhaps due to similarly well-connected surface-to-bed hydrologic systems. Improved characterization of diurnal, melt-forced and semi-diurnal, tidally-forced glacier flow provides an opportunity to further our understanding of changing basal resistance to ice flow in response to atmospheric and oceanic forcing on hourly to seasonal timescales.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C11A..08S
- Keywords:
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- 0720 Glaciers;
- CRYOSPHEREDE: 0726 Ice sheets;
- CRYOSPHEREDE: 0728 Ice shelves;
- CRYOSPHEREDE: 4207 Arctic and Antarctic oceanography;
- OCEANOGRAPHY: GENERAL