Combined near-surface geophysical measurements to characterize a firn aquifer in the southeastern part of the Greenland ice sheet
Abstract
Firn aquifers contribute to the Greenland ice sheet hydrology and mass balance estimates by storing substantial amounts of water in regions of the percolation zone where high snow accumulation and high melt conditions are found. To characterize these aquifers, we have conducted three field seasons in Southeast Greenland in the accumulation zone of the Helheim Glacier catchment between 2015-2016, deploying three non-invasive near-surface geophysical methods complementing each other to characterize the vertical structure of a firn aquifer and its variability. The methods deployed include ground-penetrating radar surveys to spatially map the water-table elevation, magnetic resonance soundings to estimate the water volume stored in the aquifer and active seismic refraction surveys to target the depth of the base of the aquifer marking the transition from water-saturated firn to ice. We observe that the water table changes in space and time are controlled by surface topography and by the response to surface meltwater input, while the aquifer base remains relatively stable (at 28 m). The water volume stored in the aquifer ranges between 210 and 1940 kg/m2 integrated over the saturated firn column and increases between April 2015 and August 2016 at one location. We complement these findings using historical airborne radar data over our field site to determine that aquifers have existed at least since 1993 (dataset starts) and have recently expanded toward the interior of the ice sheet in response to warmer surface conditions. We will discuss the impacts of these findings on current and future ice-sheet hydrology and mass-balance estimates. These measurements are available for firn-model development and validation, as well as models of englacial hydrology to determine the fate of this aquifer water.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMNS42A..01F
- Keywords:
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- 0702 Permafrost;
- CRYOSPHEREDE: 0738 Ice;
- CRYOSPHEREDE: 0758 Remote sensing;
- CRYOSPHEREDE: 0794 Instruments and techniques;
- CRYOSPHERE