Simulating feedback cycles induced by basal water in western Dronning Maud Land, Antarctica


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Thomas.Kleiner [ at ] awi.de

Abstract

The occurrence of liquid water at the base of an ice sheet is believed to be a crucial component in its dynamic evolution. If temperatures at the base locally reach the pressure melting point, basal melt water lubricates the base and thus supports basal sliding. Faster basal sliding in turn reduces internal deformation and thus the internal heat production due to strain heating. If this loss of strain heating is not counterbalanced by frictional heat due to sliding or the advection of warm ice, the base of the ice will freeze to the bedrock again. Thus the presence of liquid water can lead to a cooling and a subsequent stagnation of fast ice flow, posing a negative feedback cycle. In addition, strain heating within a temperate ice layer generates a liquid water fraction in the ice, leading to a softer material and enhanced deformation. If the horizontal or vertical advection of cold ice to the base is weak, this will lead to a positive feedback. These feedback cycles are studied along numerical simulations of the present day ice flow in the area of the western Dronning Maud Land, Antarctica, including the adjacent Brunt and Riiser- Larsen ice shelves. To investigate the influence of basal water on basal sliding and ice rheology we use the three-dimensional thermo-coupled full-Stokes model TIM-FD3 on a 2.5 km horizontal grid. We use the enthalpy gradient method to compute the thermal evolution, including the microscopic water content, in temperate ice areas. Three different flux routing algorithms for the subglacial melt water and a modified Weertman-type sliding relation are implemented in the model to account for higher sliding velocities under wet basal conditions. We present our analysis of the involved feedback mechanisms between sliding, ice deformation, temperature and rheology, which are related to the occurrence of basal water.



Item Type
Conference (Talk)
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Primary Division
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Peer revision
Not peer-reviewed
Publication Status
Published
Event Details
AGU Fall Meeting, 09 Dec 2013 - 13 Dec 2013, San Francisco.
Eprint ID
42730
Cite as
Kleiner, T. and Humbert, A. (2013): Simulating feedback cycles induced by basal water in western Dronning Maud Land, Antarctica , AGU Fall Meeting, San Francisco, 9 December 2013 - 13 December 2013 .


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