Bed conditions of Pine Island Glacier, West Antarctica

Brisbourne, Alex M. ORCID: https://orcid.org/0000-0002-9887-7120; Smith, Andy M. ORCID: https://orcid.org/0000-0001-8577-482X; Vaughan, David G. ORCID: https://orcid.org/0000-0002-9065-0570; King, Edward C. ORCID: https://orcid.org/0000-0003-3793-3915; Davies, D.; Bingham, R.G.; Smith, E.C.; Nias, I.J.; Rosier, Sebastian H.R. ORCID: https://orcid.org/0000-0003-3047-9908. 2017 Bed conditions of Pine Island Glacier, West Antarctica. Journal of Geophysical Research: Earth Surface, 122 (1). 419-433. https://doi.org/10.1002/2016JF004033

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Abstract/Summary

Although 90% of Antarctica's discharge occurs via its fast-flowing ice streams, our ability to project future ice sheet response has been limited by poor observational constraints on the ice-bed conditions used in numerical models to determine basal slip. We have helped address this observational deficit by acquiring and analyzing a series of seismic reflection profiles to determine basal conditions beneath the main trunk and tributaries of Pine Island Glacier (PIG), West Antarctica. Seismic profiles indicate large-scale sedimentary deposits. Combined with seismic reflection images, measured acoustic impedance values indicate relatively uniform bed conditions directly beneath the main trunk and tributaries, comprising a widespread reworked sediment layer with a dilated sediment lid of minimum thickness 1.5 ± 0.4 m. Beneath a slow-moving intertributary region, a discrete low-porosity sediment layer of 7 ± 3 m thickness is imaged. Despite considerable basal topography, seismic observations indicate that a till layer at the ice base is ubiquitous beneath PIG, which requires a highly mobile sediment body to maintain an abundant supply. These results are compatible with existing ice sheet models used to invert for basal shear stress: existing basal conditions upstream will not inhibit further rapid retreat of PIG if the high-friction region currently restraining flow, directly upstream of the grounding line, is breached. However, small changes in the pressure regime at the bed, as a result of stress reorganization following retreat, may result in a less-readily deformable bed and conditions which are less likely to maintain high ice-flow rates.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1002/2016JF004033
Programmes:	BAS Programmes > BAS Programmes 2015 > Ice Dynamics and Palaeoclimate
ISSN:	0148-0227
Additional Keywords:	Pine Island Glacier, bed conditions, seismic reflection, West Antarctica, ice streams, subglacial processes
Date made live:	04 Apr 2017 08:37 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/513935

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