Cryospheric and Polar Processes Seminar
Firn Aquifers: Water-laden snow on the polar ice sheets by Dr. Ted Scambos, Senior Research Scientist at ESOC and Dr. Julie Miller, Research Scientist
Abstract: Satellite algorithms using passive and active microwave data have been used to detect and map firn aquifers — water-satured layers within the porous upper layers of a glacier. The long-term freeze-thaw condition of the deep firn is determined from the evolution of the residual melt signal in the microwave data in the autumn, winter, and spring months. The algorithm performed well at tracking the full extent of aquifers around the Greenland coastline, where they had been partially constrained by airborne radar data (specifically, the reflection from the upper surface of retained liquid meltwater) after being discovered in 2011. Applying the algorithm to the Antarctic continent, several areas were identified with signals indicative of seasonal or multi-annual aquifers.
A team of NSIDC and CIRES scientists visited two of the sites in December of 2018. Using a hot-ring coring system, the team drilled into the upper firn on the Wilkins Ice Shelf and encountered a well-developed aquifer at 12 meters depth. The aquifer extended over the entire area surveyed, and likely covers the entire Wilkins Shelf based on airborne data from prior years and anecdotal observations of water-logged firn cores. A second site on the George VI Ice Shelf, with less robust indications of a multi-annual aquifer, showed multiple thick (20 cm) ice layers but no liquid water.
The presence of an aquifer on Wilkins Ice Shelf, which has experienced several ice shelf disintegration episodes similar to those of the Larsen B ice shelf, suggests that aquifers can support hydrofracture-driven enhanced fracturing. Thus areas of other ice shelves on the Antarctic coast where conditions in the future approach those present on the Wilkins Ice Shelf now would be susceptible to rapid ice shelf retreat, and subsequent faster flow from feeder glaciers.
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