Temporal variations in the flow of a large Antarctic ice stream controlled by tidally induced changes in the subglacial water system

Rosier, S.H.R. ORCID: https://orcid.org/0000-0003-3047-9908; Gudmundsson, G.H. ORCID: https://orcid.org/0000-0003-4236-5369; Green, J.A.M.. 2015 Temporal variations in the flow of a large Antarctic ice stream controlled by tidally induced changes in the subglacial water system. The Cryosphere, 9 (4). 1649-1661. 10.5194/tc-9-1649-2015

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Abstract/Summary

Observations show that the flow of Rutford Ice Stream (RIS) is strongly modulated by the ocean tides, with the strongest tidal response at the 14.77 day tidal period (Msf). This is striking because this period is absent in the tidal forcing. A number of mechanisms have been proposed to account for this effect, yet previous modeling studies have struggled to match the observed large amplitude and decay length scale. We use a nonlinear 3-D viscoelastic full-Stokes model of ice-stream flow to investigate this open issue. We find that the long period Msf modulation of ice-stream velocity observed in data cannot be reproduced quantitatively without including a coupling between basal sliding and tidal subglacial water pressure variations. Furthermore, the subglacial water system must be highly conductive and at low effective pressure, and the relationship between sliding velocity and effective pressure highly nonlinear in order for the model results to match GPS measurements. Hydrological and basal sliding model parameters that produced a best fit to observations were a mean effective pressure N of 105 kPa, subglacial drainage system conductivity K of 7 × 109 m2d-1, with sliding law exponents m = 3 and q =10. Coupled model results show the presence of tides result in a ~ 12% increase in mean surface velocity. Observations of tidally-induced variations in flow of ice-streams provide stronger constraints on basal sliding processes than provided by any other set of measurements.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.5194/tc-9-1649-2015
Programmes:	BAS Programmes > BAS Programmes 2015 > Ice Dynamics and Palaeoclimate
ISSN:	19940416
Date made live:	15 Jun 2015 10:33 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/510051

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.5194/tc-9-1649-2015

Programmes:

BAS Programmes > BAS Programmes 2015 > Ice Dynamics and Palaeoclimate

ISSN:

19940416

Date made live:

15 Jun 2015 10:33 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/510051