Hydrologic Properties of a Highly Permeable Firn Aquifer in the Wilkins Ice Shelf, Antarctica. Issue 22 (15th November 2020)

• Record Type: Journal Article
• Authors: Montgomery, Lynn; Miège, Clément; Miller, Julie; Scambos, Ted A.; Wallin, Bruce; Miller, Olivia; Solomon, D. Kip; Forster, Richard; Koenig, Lora
• Is Part Of: Geophysical research letters. Volume 47:Issue 22(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-15
• Subjects: firn aquifer -- hydrology -- ice shelf -- Antarctica -- hydraulic conductivity -- water flow; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL089552
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We present measurements of the density, hydraulic conductivity, and specific discharge of a widespread firn aquifer in Antarctica, within the Wilkins Ice Shelf. At the field site, the aquifer is 16.2 m thick, starting at 13.4 m from the snow surface and transitioning from water‐saturated firn to ice at 29.6 m. Hydraulic conductivity derived from slug tests show a geometric mean value of 1.4 ± 1.2 × 10 −4 m s −1, equivalent to permeability of 2.6 ± 2.2 × 10 −11 m 2 . A borehole dilution test indicates an average specific discharge value of 1.9 ± 2.8 × 10 −6 m s −1 . Ground‐penetrating radar profiles and a groundwater flow model show the aquifer is draining laterally into a large nearby rift. Our findings indicate that the firn aquifer in the vicinity of the field site is likely not in a steady state and its presence likely contributed to past ice shelf instability. Plain Language Summary: Firn aquifers occur in areas of high melt and snow accumulation when meltwater percolates into firn (compacted snow older than 1 year) pore space and is stored throughout the winter without refreezing. In December 2018, a field team traveled to the Wilkins Ice Shelf on the Antarctic Peninsula and drilled into an aquifer. We used a combination of hydrology and ground‐penetrating radar measurements to show that water is flowing laterally through porous buried snow and draining into a nearby rift. Firn aquifers are important since they allow meltwater to be stored at depth, possibly running off into cracks, crevasses, or rifts and increasing fracture depth, thereby leading to ice shelf destabilization. Key Points: An extensive perennial firn aquifer within the Wilkins Ice Shelf is characterized for its hydrologic properties Field data and modeling show the aquifer has high permeability and is flowing into a nearby rift Past disintegration events on the Wilkins Ice Shelf with hydrofracture characteristics are likely a result of the aquifer's presence