The evolution of isolated cavities and hydraulic connection at the glacier bed – Part 1: Steady states and friction laws
Models of subglacial drainage and of cavity formation generally assume that the glacier bed is pervasively hydraulically connected. A growing body of field observations indicates that this assumption is frequently violated in practice. In this paper, I use an extension of existing models of steady-s...
Published in: | The Cryosphere |
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Main Author: | |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Copernicus Publications
2023
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Subjects: | |
Online Access: | https://doi.org/10.5194/tc-17-4797-2023 https://noa.gwlb.de/receive/cop_mods_00069891 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00068259/tc-17-4797-2023.pdf https://tc.copernicus.org/articles/17/4797/2023/tc-17-4797-2023.pdf |
Summary: | Models of subglacial drainage and of cavity formation generally assume that the glacier bed is pervasively hydraulically connected. A growing body of field observations indicates that this assumption is frequently violated in practice. In this paper, I use an extension of existing models of steady-state cavitation to study the formation of hydraulically isolated, uncavitated, low-pressure regions of the bed, which would become flooded if they had access to the subglacial drainage system. I also study their natural counterpart, hydraulically isolated cavities that would drain if they had access to the subglacial drainage system. I show that connections to the drainage system are made at two different sets of critical effective pressure, a lower one at which uncavitated low-pressure regions connect to the drainage system and a higher one at which isolated cavities do the same. I also show that the extent of cavitation, determined by the history of connections made at the bed, has a dominant effect on basal drag while remaining outside the realm of previously employed basal friction laws: changes in basal effective pressure alone may have a minor effect on basal drag until a connection between a cavity and an uncavitated low-pressure region of the bed is made, at which point a drastic and irreversible drop in drag occurs. These results point to the need to expand basal friction and drainage models to include a description of basal connectivity. |
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