Evidence for a grounding line fan at the onset of a basal channel under the ice shelf of Support Force Glacier, Antarctica, revealed by reflection seismics

Hofstede, C.; Beyer, S.; Corr, H.; Eisen, O.; Hattermann, T.; Helm, V.; Neckel, N.; Smith, E.C.; Steinhage, D.; Zeising, O.; Humbert, A.. 2021 Evidence for a grounding line fan at the onset of a basal channel under the ice shelf of Support Force Glacier, Antarctica, revealed by reflection seismics. The Cryosphere, 15 (3). 1517-1535. 10.5194/tc-15-1517-2021

Before downloading, please read NORA policies.

Preview

Text (Open Access)
© Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License.
tc-15-1517-2021.pdf - Published Version
Available under License Creative Commons Attribution 4.0.
Download (27MB) | Preview

Official URL: https://tc.copernicus.org/articles/15/1517/2021/

Abstract/Summary

Curvilinear channels on the surface of an ice shelf indicate the presence of large channels at the base. Modelling studies have shown that where these surface expressions intersect the grounding line, they coincide with the likely outflow of subglacial water. An understanding of the initiation and the ice–ocean evolution of the basal channels is required to understand the present behaviour and future dynamics of ice sheets and ice shelves. Here, we present focused active seismic and radar surveys of a basal channel, ∼950 m wide and ∼200 m high, and its upstream continuation beneath Support Force Glacier, which feeds into the Filchner Ice Shelf, West Antarctica. Immediately seaward from the grounding line, below the basal channel, the seismic profiles show an ∼6.75 km long, 3.2 km wide and 200 m thick sedimentary sequence with chaotic to weakly stratified reflections we interpret as a grounding line fan deposited by a subglacial drainage channel directly upstream of the basal channel. Further downstream the seabed has a different character; it consists of harder, stratified consolidated sediments, deposited under different glaciological circumstances, or possibly bedrock. In contrast to the standard perception of a rapid change in ice shelf thickness just downstream of the grounding line, we find a flat topography of the ice shelf base with an almost constant ice thickness gradient along-flow, indicating only little basal melting, but an initial widening of the basal channel, which we ascribe to melting along its flanks. Our findings provide a detailed view of a more complex interaction between the ocean and subglacial hydrology to form basal channels in ice shelves.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.5194/tc-15-1517-2021
ISSN:	1994-0416
Date made live:	30 Mar 2021 08:41 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/529978

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.5194/tc-15-1517-2021

ISSN:

1994-0416

Date made live:

30 Mar 2021 08:41 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/529978