Bed roughness as a control on the drainage of subglacial water
Abstract
Drainage through subglacial water systems depends on supply, storage, and routing. Most deterministic models of drainage make an a priori assumption about how the water and overlying ice interact. These interactions determine basal water pressure, and from that sliding rules are employed to determine the slip rate of ice across the bed. Principally, competition between opening and closing of the water system determines this pressure. Channels or linked cavities, for example, each have different empiricisms that determine how they open or close, constructed to be consistent with field observations. These empiricisms are implicit in models of drainage and slip to determine glacier and ice sheet movement.
At scales much larger than individual channels or linked cavities, the empiricisms potentially fade. Linked cavities and channels both become ``sub grid'' as individual pieces of the water network are averaged over space. Conspicuously absent from these formulations are intermediate-scale descriptions based on data from ice sheet beds. The question then becomes whether there is an appropriate description at a larger scale that encompasses a relevant distribution of topography and water along the bed. In this presentation, we modify existing drainage theory to accommodate this broader scale information. We employ roughness scales to determine rates of change of the water system along the bed. Bed roughness can be determined from airborne geophysical surveys and allows for extensive measures of bed characteristics. We examine how these opening and closing rules can be modified and how the existing formulations can be succinctly changed to incorporate data. Time permitting, we will show how the spatial structure of bed information measured from ice sheets can contribute to drainage system behaviors.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C51E1107C
- Keywords:
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- 0720 Glaciers;
- CRYOSPHEREDE: 0726 Ice sheets;
- CRYOSPHEREDE: 0774 Dynamics;
- CRYOSPHEREDE: 0776 Glaciology;
- CRYOSPHERE