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.
1769-1782
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
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Ward, Tyler
42223a20-f8bd-4299-9e87-5d980dadabf1
Young, David
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July 2019
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
Ward, Tyler
42223a20-f8bd-4299-9e87-5d980dadabf1
Young, David
05bfdb8c-9675-470a-9dcb-5af247e1b4ca
Hart, Jane K., Martinez, Kirk, Basford, Philip J., Clayton, Alexander, Bragg, Graeme McLachlan, Ward, Tyler 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, 44 (9), .
(doi:10.1002/esp.4611).
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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Hart_et_al-2019-Earth_Surface_Processes_and_Landforms
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Accepted/In Press date: 13 March 2019
e-pub ahead of print date: 1 May 2019
Published date: July 2019
Identifiers
Local EPrints ID: 430771
URI: http://eprints.soton.ac.uk/id/eprint/430771
ISSN: 0197-9337
PURE UUID: 3da96f4f-e3c7-403d-a42b-7ac0caaa8e63
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Date deposited: 10 May 2019 16:30
Last modified: 16 Mar 2024 04:29
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Author:
Kirk Martinez
Author:
Alexander Clayton
Author:
Graeme McLachlan Bragg
Author:
Tyler Ward
Author:
David Young
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