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Record Search Query:
Impact of Supraglacial Lakes on Ice-Shelf Stability
Entry ID: USAP-1443126_1

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Summary
Abstract:

Meltwater lakes that sit on top of Antarctica's floating ice shelves have likely contributed to the dramatic changes seen in Antarctica's glacial ice cover over the past two decades. In 2002, the 1,600-square-kilometer Larsen B Ice Shelf located on the Eastern side of the Antarctic Peninsula, for example, broke into thousands of small icebergs, which subsequently floated away as a result of the ...


The proposed project seeks to experimentally verify a theory of ice-shelf instability proposed to explain the explosive break-up of Larsen B Ice Shelf in 2002. This theory holds that the filling and draining of supraglacial lakes on floating ice shelves induces sufficient flexure stress within the ice to (a) induce upward/downward propagating fractures originating at the base/surface of the ice shelf that (b) dissect the ice shelf into fragments that tend to have widths less than about half the ice thickness. The significance of narrow widths is that they promote capsize of the ice-shelf fragments during the break-up process. This capsize releases large amounts of gravitational potential energy (comparable to thousands of kilotons of TNT for the Larsen B Ice Shelf) thereby promoting explosiveness of the Larsen B event. The observational motivation for experimentally verifying the surface-lake mechanism for ice-shelf breakup is based on the fact that >2,000 surface lakes developed on the Larsen B Ice Shelf in the decade prior to its break up, and that these lakes were observed (via satellite imagery) to drain in a coordinated fashion during the day prior to the initiation of the break up.


The field-observation component of the project will focus on a supraglacial lake on the McMurdo Ice Shelf where there is persistent summer season surface melting. The lake will be studied during a single provisional field season to determine whether grooming of surrounding surface streams and shorelines with heavy construction equipment will allow surface water to be manually encouraged to fill the lake. If successfully encouraged to develop, the McMurdo Ice Shelf surface lake will allow me asurements of key ice-shelf flexure and stress variables needed to develop the theory of ice-shelf surface lakes without having to access the much more logistically demanding surface lakes of ice-shelves located elsewhere in Antarctica. Data to be gathered during the 6-week provisional field season include: energy- and water-balance parameters determining how the surface lake grows and fills, and various global positioning system measurements of the vertical bending of the ice sheet in response to the changing meltwater load contained within the surface lake. These data will be used to (1) constrain a computer model of viscoelastic flexure and possible fracture of the ice shelf in response to the increasing load of meltwater in the lake, and (2) determine whether continued study of the incipient surface-meltwater lake features on the McMurdo Ice Shelf provides a promising avenue for constraining the more-general behavior of surface meltwater lakes on other ice shelves located in warmer parts of Antarctica. Computer models constrained by the observational data obtained from the field project will inform energy- and water-balance models of ice shelves in general, and allow more accurate forecasts of changing ice-shelf conditions surrounding the inland ice of Antarctica. The project will create the first-ever ground-based observations useful for spawning the development of models capable of predicting viscoelastic and fracture behavior of ice shelves in response to supraglacial lake evolution, including slow changes due to energy balance effects, as well as fast changes due to filling and draining.


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Description: NSF Award Abstract
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Data Set Citation
Dataset Originator/Creator: MacAyeal, Douglas and Alison Banwell
Dataset Title: McMurdo Ice Shelf GPS survey of vertical motion
Dataset Publisher: USAP-DC
Version: 1
Dataset DOI: 10.15784/601107
Online Resource: http://www.usap-dc.org/view/dataset/601107

Dataset Originator/Creator: MacAyeal, Douglas and Alison Banwell
Dataset Title: McMurdo Ice Shelf AWS data
Dataset Publisher: USAP-DC
Version: 1
Dataset DOI: 10.15784/601107
Online Resource: http://www.usap-dc.org/view/dataset/601106
Temporal Coverage
Start Date: 2015-09-01T00:00:00.000Z
Stop Date: 2017-08-31T23:59:59.999Z
Ancillary Keywords
Data Set Progress
COMPLETE
Data Center
United States Antarctic Program Data Center
Data Center URL: http://www.usap-dc.org/

Data Center Personnel
Name: Data Manager
Email: info at usap-dc.org
Contact Address:
Lamont-Doherty Earth Observatory
61 Route 9W
City: Palisades
Province or State: NY
Postal Code: 10964
Country: USA
Personnel
Douglas MacAyeal
Role: INVESTIGATOR
Email: drm7 at midway.uchicago.edu
Contact Address:
University of Chicago
Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 2018-07-23
Last DIF Revision Date: 2018-09-06