Pattern-forming instabilities in the coupling of ice sheets and subglacial drainage systems
Sharp spatial changes discovered in the basal conditions of an ice sheet do not always have an obvious source. By modelling instabilities in the coupling of an ice sheet and subglacial drainage system, we describe physical feedback mechanisms that force the formation of sharp spatial structures in b...
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ftunivbritcolcir:oai:circle.library.ubc.ca:2429/65843 2023-05-15T16:40:17+02:00 Pattern-forming instabilities in the coupling of ice sheets and subglacial drainage systems Whiteford, Arran 2018 http://hdl.handle.net/2429/65843 eng eng University of British Columbia Attribution-NonCommercial-ShareAlike 4.0 International http://creativecommons.org/licenses/by-nc-sa/4.0/ CC-BY-NC-SA Text Thesis/Dissertation 2018 ftunivbritcolcir 2019-10-15T18:26:02Z Sharp spatial changes discovered in the basal conditions of an ice sheet do not always have an obvious source. By modelling instabilities in the coupling of an ice sheet and subglacial drainage system, we describe physical feedback mechanisms that force the formation of sharp spatial structures in basal conditions and ice flow. This model predicts the spontaneous formation of periodic subglacial `sticky spot'-lake pairs, that correspond in shape to previous empirical and modelled descriptions of similar structures. The instability that forms this structure is driven by a feedback whereby periodic humps in ice thickness redirect subglacial water to slippery spots that lie immediately downstream of the ice humps: the slippery regions increase ice flux into the ice humps, making them grow. Scaling a one-dimensional model ice sheet coupled to a basal drainage system, we find conditions for the instability with linear stability analysis. Solutions in the full nonlinear model are simulated numerically, using operator splitting and finite difference methods. The instability requires a bed permeability weakly dependent on water pressure changes, negligible bed slopes, and a water velocity much greater than ice velocity. The `sticky spot'-lake pairs are predicted to form with periodic spacing and migrate upstream. Science, Faculty of Earth, Ocean and Atmospheric Sciences, Department of Graduate Thesis Ice Sheet University of British Columbia: cIRcle - UBC's Information Repository Humps ENVELOPE(-57.450,-57.450,-63.983,-63.983) Spot Lake ENVELOPE(-108.751,-108.751,59.550,59.550) |
institution |
Open Polar |
collection |
University of British Columbia: cIRcle - UBC's Information Repository |
op_collection_id |
ftunivbritcolcir |
language |
English |
description |
Sharp spatial changes discovered in the basal conditions of an ice sheet do not always have an obvious source. By modelling instabilities in the coupling of an ice sheet and subglacial drainage system, we describe physical feedback mechanisms that force the formation of sharp spatial structures in basal conditions and ice flow. This model predicts the spontaneous formation of periodic subglacial `sticky spot'-lake pairs, that correspond in shape to previous empirical and modelled descriptions of similar structures. The instability that forms this structure is driven by a feedback whereby periodic humps in ice thickness redirect subglacial water to slippery spots that lie immediately downstream of the ice humps: the slippery regions increase ice flux into the ice humps, making them grow. Scaling a one-dimensional model ice sheet coupled to a basal drainage system, we find conditions for the instability with linear stability analysis. Solutions in the full nonlinear model are simulated numerically, using operator splitting and finite difference methods. The instability requires a bed permeability weakly dependent on water pressure changes, negligible bed slopes, and a water velocity much greater than ice velocity. The `sticky spot'-lake pairs are predicted to form with periodic spacing and migrate upstream. Science, Faculty of Earth, Ocean and Atmospheric Sciences, Department of Graduate |
format |
Thesis |
author |
Whiteford, Arran |
spellingShingle |
Whiteford, Arran Pattern-forming instabilities in the coupling of ice sheets and subglacial drainage systems |
author_facet |
Whiteford, Arran |
author_sort |
Whiteford, Arran |
title |
Pattern-forming instabilities in the coupling of ice sheets and subglacial drainage systems |
title_short |
Pattern-forming instabilities in the coupling of ice sheets and subglacial drainage systems |
title_full |
Pattern-forming instabilities in the coupling of ice sheets and subglacial drainage systems |
title_fullStr |
Pattern-forming instabilities in the coupling of ice sheets and subglacial drainage systems |
title_full_unstemmed |
Pattern-forming instabilities in the coupling of ice sheets and subglacial drainage systems |
title_sort |
pattern-forming instabilities in the coupling of ice sheets and subglacial drainage systems |
publisher |
University of British Columbia |
publishDate |
2018 |
url |
http://hdl.handle.net/2429/65843 |
long_lat |
ENVELOPE(-57.450,-57.450,-63.983,-63.983) ENVELOPE(-108.751,-108.751,59.550,59.550) |
geographic |
Humps Spot Lake |
geographic_facet |
Humps Spot Lake |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_rights |
Attribution-NonCommercial-ShareAlike 4.0 International http://creativecommons.org/licenses/by-nc-sa/4.0/ |
op_rightsnorm |
CC-BY-NC-SA |
_version_ |
1766030670119829504 |