Physical Conditions of Fast Glacier Flow 1: Measurements From Boreholes Drilled to the Bed of Store Glacier, West Greenland

Samuel Doyle, Bryn Hubbard, P. Christoffersen, T. J. Young, C. Hofstede, M. Bougamont, J. E. Box, Alun Hubbard

Allbwn ymchwil: Cyfraniad at gyfnodolynErthygladolygiad gan gymheiriaid

45 Dyfyniadau (Scopus)
166 Wedi eu Llwytho i Lawr (Pure)

Crynodeb

Marine-terminating outlet glaciers of the Greenland ice sheet make significant contributions to global sea level rise, yet the conditions that facilitate their fast flow remain poorly constrained owing to a paucity of data. We drilled and instrumented seven boreholes on Store Glacier, Greenland, to monitor subglacial water pressure, temperature, electrical conductivity and turbidity along with englacial ice temperature and deformation. These observations were supplemented by surface velocity and meteorological measurements to gain insight into the conditions and mechanisms of fast glacier flow. Located 30km from the calving front, each borehole drained rapidly on attaining ∼600m depth indicating a direct connection with an active subglacial hydrological system. Persistently high subglacial water pressures indicate low effective pressure (180 − 280 kPa), with small amplitude variations correlated with notable peaks in surface velocity driven by the diurnal melt cycle and longer periods of melt and rainfall. The englacial deformation profile determined from borehole tilt measurements indicates that 63-71% of total ice motion occurred at the bed, with the remaining 29-37% predominantly attributed to enhanced deformation in the lowermost 50-100 m of the ice column. We interpret this lowermost 100m to be formed of warmer, pre-Holocene ice overlying a thin (0 − 8 m) layer of temperate basal ice. Our observations are consistent with a spatially-extensive and persistently-inefficient subglacial drainage system that we hypothesize comprises drainage both at the ice-sediment interface and through subglacial sediments. This configuration has similarities to that interpreted beneath dynamically-analogous Antarctic ice streams, Alaskan tidewater glaciers, and glaciers in surge
Iaith wreiddiolSaesneg
Tudalennau (o-i)324-348
Nifer y tudalennau25
CyfnodolynJournal of Geophysical Research: Earth Surface
Cyfrol123
Rhif cyhoeddi2
Dyddiad ar-lein cynnar21 Ion 2018
Dynodwyr Gwrthrych Digidol (DOIs)
StatwsCyhoeddwyd - 24 Chwef 2018

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