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Subglacial bathymetry and sediment distribution beneath Pine Island Glacier ice shelf modeled using aerogravity and in situ geophysical data: new results

Citation

Muto, A and Peters, LE and Gohl, K and Sasgen, I and Alley, RB and Anandakrishnan, S and Riverman, KL, Subglacial bathymetry and sediment distribution beneath Pine Island Glacier ice shelf modeled using aerogravity and in situ geophysical data: new results, Earth and Planetary Science Letters, 433 pp. 63-75. ISSN 0012-821X (2016) [Refereed Article]

Copyright Statement

ę 2015 Elsevier B.V. All rights reserved.

DOI: doi:10.1016/j.epsl.2015.10.037

Abstract

Pine Island Glacier (PIG) in the Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS) is losing mass and contributing to global sea-level rise at an accelerating rate. Although recent observations and modeling have identified the incursion of relatively warm Circumpolar Deep Water (CDW) beneath the PIG ice shelf (PIGIS) as the main driver of this ice-mass loss, the lack of precise bathymetry limits furthering our understanding of the iceľocean interactions and improving the accuracy of modeling. Here we present updated bathymetry and sediment distribution beneath the PIGIS, modeled by the inversion of aerogravity data with constraints from active-source seismic data, observations from an autonomous underwater vehicle, and the regional gravity-anomaly field derived from satellite gravity observations. Modeled bathymetry shows a submarine ridge beneath the middle of PIGIS that rises ∼350 to 400 m above the surrounding sea floor, with a minimum water-column thickness of ∼200 m above it. This submarine ridge continues across the whole width of the 45-km wide ice shelf, with no deep troughs crossing it, confirming the general features of the previously predicted sub-ice-shelf ocean circulation. However, the relatively low resolution of the aerogravity data and limitations in our inversion method leave a possibility that there is an undetected, few-kilometers-wide or narrower trough that may alter the predicted sub-ice-shelf ocean circulation. Modeled sediment distribution indicates a sedimentary basin of up to ∼800 m thick near the current grounding zone of the main PIG trunk and extending farther inland, and a region seaward of the submarine ridge where sediments are thin or absent with exposed crystalline basement that extends seaward into Pine Island Bay. Therefore, the submarine ridge marks the transition from a thick sedimentary basin providing a smooth interface over which ice could flow easily by sliding or sediment deformation, to a region with no to little sediments and instead a rough interface over which ice flows mainly by deformation. We hypothesize that the post-Last Glacial Maximum retreat of PIG stabilized at this location because of the spatial transition in basal conditions. This in turn supports the hypothesis that the recent retreat of PIG was strongly forced, probably by changes in ocean circulation, rather than occurring because of ongoing response to the end of the ice age or other changes inland of or beneath PIG.

Item Details

Item Type:Refereed Article
Keywords:gravity, ice shelves, ocean cavity, Antarctica, sub-ice-shelf bathymetry, subglacial geology
Research Division:Earth Sciences
Research Group:Physical Geography and Environmental Geoscience
Research Field:Glaciology
Objective Division:Environment
Objective Group:Climate and Climate Change
Objective Field:Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts)
Author:Peters, LE (Dr Leo Peters)
ID Code:104293
Year Published:2016
Web of Science® Times Cited:9
Deposited By:Oceans and Cryosphere
Deposited On:2015-11-06
Last Modified:2017-11-17
Downloads:0

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