Hydraulic run-away: a tnechanistn for therll1ally regulated surges of ice sheets
ABSTRACT. By using a simple paramet erized model of thermomechanically coupled flow in cold ice sheets, together with a physically based sliding law which includes a description of basal drainage, we show that relationships between ice flux and ice thickness can realistically be multi-valued, and he...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.304.460 http://www.maths.ox.ac.uk/%7Efowler/papers/1995.3.pdf |
| Summary: | ABSTRACT. By using a simple paramet erized model of thermomechanically coupled flow in cold ice sheets, together with a physically based sliding law which includes a description of basal drainage, we show that relationships between ice flux and ice thickness can realistically be multi-valued, and hence that hydraulically induced surges can occur. 'vVe term this mechanism h)draulic TllIl-aWa), as it relies on the positive feed-back between sliding velocity and basal melt production. For this feedback to operate, it is essential that water pressure increases with water storage. This is consistent with various recent ideas concerning drainage under ice sheets, be it through a system of canals, a di stributed film or a subglacial aquifer. For confined flows, such as valley glaciers (e.g. Trapridge Glacier) or topographically constrained ice streams (e.g. Hudson Strait in the Laurentide ice sheet) , which are underlain by sufficiently deformable sediment, we can expect thermally regulated surges to occur, while in a laterally unconfined drainage basin (such as that which flows into the Ross Ice Shel!), we might expect ice streams to develop. 1. |
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