Surface Meltwater Impounded by Seasonal Englacial Storage in West Greenland

A K Kendrick,L B Lok,A Hubbard,P Christoffersen,W Chu,B Hubbard,D M Schroeder,J E Box,K W Nicholls,S H Doyle,J Todd,T J Young,P V Brennan

doi:10.1029/2018gl079787

Abstract

AbstractThe delivery of surface meltwater through englacial drainage systems to the bed of the Greenland Ice Sheet modulates ice flow through basal lubrication. Recent studies in Southeast Greenland have identified a perennial firn aquifer; however, there are few observations quantifying the input or residence time of water within the englacial system and it remains unknown whether water can be stored within solid ice. Using hourly stationary radar measurements, we present observations of englacial and episodic subglacial water in the ablation zone of Store Glacier in West Greenland. We find significant storage of meltwater in solid ice damaged by crevasses extending down to 48 m below the ice surface during the summer, which is released or refrozen during winter. This is a significant hydrological component newly observed in the ablation zone of Greenland that could delay the delivery of meltwater to the bed, changing the ice dynamic response to surface meltwater.

Highlights

This radiometric time series of phase-sensitive radar sounding observations offers an unprecedented view of the interaction between the englacial and subglacial water drainage systems of the Greenland Ice Sheet
Our results demonstrate that englacial water storage may be a pervasive, yet overlooked feature of ice sheet hydrology, occurring in the thick firn layers (Forster et al, 2013) and in bare ice regions (Cooper et al, 2018)
Without the incorporation of regional englacial storage delaying a fraction of the surface melt water from reaching the bead, model-based assessments of the Greenland Ice Sheet will not fully capture the dynamic response to surface melt water input

Summary

Introduction

Meltwater drainage from the surface to the bed along the margin of the Greenland Ice Sheet produces transient ice velocity fluctuations by enhancing basal sliding through hydraulic pressurization (Andrews et al, 2014; Bartholomew et al, 2012; Schoof, 2010; Zwally et al, 2002). Comparable surface meltwater production on the same glacier can lead to notable flow acceleration in 1 year and produce a diminished velocity response in another (Fitzpatrick et al, 2013; Joughin et al, 2013; Moon et al, 2014) This variation across Greenland is likely closely linked to the flow, storage, and distribution of water among and within the englacial and subglacial drainage systems (Andrews et al, 2014; Bartholomew et al, 2012; Sole et al, 2011). The prevalence of water storage outside the permeable firn regions and the fraction of annual meltwater stored in bare ice remains unknown

Methods

Discussion

Conclusion