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Tidal pressurization of the ocean cavity near an Antarctic ice shelf grounding line

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posted on 2023-05-20, 12:14 authored by Begeman, CB, Tulaczyk, S, Padman, L, Matt KingMatt King, Siegfried, MR, Hodson, TO, Fricker, HA
Mass loss from the Antarctic ice sheet is sensitive to conditions in ice shelf grounding zones, the transition between grounded and floating ice. To observe tidal dynamics in the grounding zone, we moored an ocean pressure sensor to Ross Ice Shelf, recording data for 54 days. In this region the ice shelf is brought out of hydrostatic equilibrium by the flexural rigidity of ice, yet we found that tidal pressure variations at a constant geopotential surface were similar within and outside of the grounding zone. This implies that the grounding zone ocean cavity was overpressurized at high tide and underpressurized at low tide by up to 10 kPa with respect to glaciostatic pressure at the ice shelf base. Phase lags between ocean pressure and vertical ice shelf motion were tens of minutes for diurnal and semidiurnal tides, an effect that has not been incorporated into ocean models of tidal currents below ice shelves. These tidal pressure variations may affect the production and export of meltwater in the subglacial environment and may increase basal crevasse heights in the grounding zone by several meters, according to linear elastic fracture mechanics. We find anomalously high tidal energy loss at the K1 constituent in the grounding zone and hypothesize that this could be explained by seawater injection into the subglacial environment at high tide or internal tide generation through interactions with topography. These observations lay the foundation for improved representation of the grounding zone and its tidal dynamics in ocean circulation models of sub–ice shelf cavities.

History

Publication title

Journal of Geophysical Research: Oceans

Volume

125

Issue

4

Article number

e2019JC015562

Number

e2019JC015562

ISSN

2169-9291

Department/School

School of Geography, Planning and Spatial Sciences

Publisher

Wiley-Blackwell Publishing Ltd

Place of publication

United States

Rights statement

Copyright 2020 American Geophysical Union

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences

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