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Surface melt-driven seasonal behaviour (englacial and subglacial) from a soft-bedded temperate glacier recorded by in situ wireless probes

Surface melt-driven seasonal behaviour (englacial and subglacial) from a soft-bedded temperate glacier recorded by in situ wireless probes
Surface melt-driven seasonal behaviour (englacial and subglacial) from a soft-bedded temperate glacier recorded by in situ wireless probes
We investigate the spatial and temporal englacial and subglacial processes associated with a temperate glacier resting on a deformable bed using the unique Glacsweb wireless in situ probes (embedded in the ice and the till) combined with other techniques (including ground penetrating radar (GPR) and borehole analysis). During the melt season (spring, summer and autumn), high surface melt leads to high water pressures in the englacial and subglacial environment. Winter is characterised by no surface melting on most days (‘base’) apart from a series of positive degree days. Once winter begins, a diurnal water pressure cycle is established in the ice and at the ice/sediment interface, with direct meltwater inputs from the positive degree days and a secondary slower englacial pathway with a five day lag. This direct surface melt also drives water pressure changes in the till. Till deformation occurred throughout the year, with the winter rate approximately 60% that of the melt season. We were able to show the bed comprised patches of till with different strengths, and were able to estimate their size, relative percentage and temporal stability. We show that the melt season is characterised by a high pressure distributed system, and winter by a low pressure channelized system. We contrast this with studies from Greenland (overlying rigid bedrock), where the opposite was found. We argue our results are typical of soft bedded glaciers with low englacial water content, and suggest this type of glacier can rapidly respond to surface–driven melt. Based on theoretical and field results we suggest that the subglacial hydrology comprises a melt season distributed system dominated by wide anastomosing broad flat channels and thin water sheets, which may become more channelized in winter, and more responsive to changes in meltwater inputs.
0197-9337
Hart, Jane K.
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Martinez, Kirk
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Basford, Philip J.
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Clayton, Alexander
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Bragg, Graeme McLachlan
b5fd19b9-1a51-470b-a226-2d4dd5ff447a
Robson, Benjamin A.
ea6a160c-5678-4de6-be5b-4a9686891f12
Young, David
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Hart, Jane K.
e949a885-7b26-4544-9e15-32ba6f87e49a
Martinez, Kirk
5f711898-20fc-410e-a007-837d8c57cb18
Basford, Philip J.
efd8fbec-4a5f-4914-bf29-885b7f4677a7
Clayton, Alexander
bb78b742-1324-4aa1-b6af-f75a1e60e01c
Bragg, Graeme McLachlan
b5fd19b9-1a51-470b-a226-2d4dd5ff447a
Robson, Benjamin A.
ea6a160c-5678-4de6-be5b-4a9686891f12
Young, David
05bfdb8c-9675-470a-9dcb-5af247e1b4ca

Hart, Jane K., Martinez, Kirk, Basford, Philip J., Clayton, Alexander, Bragg, Graeme McLachlan, Robson, Benjamin A. and Young, David (2019) Surface melt-driven seasonal behaviour (englacial and subglacial) from a soft-bedded temperate glacier recorded by in situ wireless probes. Earth Surface Processes and Landforms, 10 (1599). (doi:10.1002/esp.4611).

Record type: Article

Abstract

We investigate the spatial and temporal englacial and subglacial processes associated with a temperate glacier resting on a deformable bed using the unique Glacsweb wireless in situ probes (embedded in the ice and the till) combined with other techniques (including ground penetrating radar (GPR) and borehole analysis). During the melt season (spring, summer and autumn), high surface melt leads to high water pressures in the englacial and subglacial environment. Winter is characterised by no surface melting on most days (‘base’) apart from a series of positive degree days. Once winter begins, a diurnal water pressure cycle is established in the ice and at the ice/sediment interface, with direct meltwater inputs from the positive degree days and a secondary slower englacial pathway with a five day lag. This direct surface melt also drives water pressure changes in the till. Till deformation occurred throughout the year, with the winter rate approximately 60% that of the melt season. We were able to show the bed comprised patches of till with different strengths, and were able to estimate their size, relative percentage and temporal stability. We show that the melt season is characterised by a high pressure distributed system, and winter by a low pressure channelized system. We contrast this with studies from Greenland (overlying rigid bedrock), where the opposite was found. We argue our results are typical of soft bedded glaciers with low englacial water content, and suggest this type of glacier can rapidly respond to surface–driven melt. Based on theoretical and field results we suggest that the subglacial hydrology comprises a melt season distributed system dominated by wide anastomosing broad flat channels and thin water sheets, which may become more channelized in winter, and more responsive to changes in meltwater inputs.

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Accepted/In Press date: 13 March 2019
e-pub ahead of print date: 1 May 2019

Identifiers

Local EPrints ID: 430771
URI: https://eprints.soton.ac.uk/id/eprint/430771
ISSN: 0197-9337
PURE UUID: 3da96f4f-e3c7-403d-a42b-7ac0caaa8e63
ORCID for Jane K. Hart: ORCID iD orcid.org/0000-0002-2348-3944
ORCID for Kirk Martinez: ORCID iD orcid.org/0000-0003-3859-5700
ORCID for Philip J. Basford: ORCID iD orcid.org/0000-0001-6058-8270
ORCID for Graeme McLachlan Bragg: ORCID iD orcid.org/0000-0002-5201-7977

Catalogue record

Date deposited: 10 May 2019 16:30
Last modified: 20 Jul 2019 01:25

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