A Physical Model of Moulin Formation and Evolution on the Greenland Ice Sheet
Abstract
Nearly all proglacial water discharge from the Greenland Ice Sheet is routed englacially via moulins. Identification of these moulins in high-resolution imagery is a frequent topic of study, but the processes controlling how and where moulins form remain poorly understood. Because moulins may reasonably compose approximately 10-15% of the englacial-subglacial hydrologic system, the evolution and shape of moulins can alter both the timing and variability of meltwater inputs to the bed. This evolution can impact both the form of the subglacial hydrologic system and associated response of ice motion. Here, we develop a physical model of moulin formation and evolution to constrain the role of englacial processes in shaping the form and structure of the subglacial hydrologic system. Within this model, moulin geometry is controlled by a balance of viscous and elastic deformation and is dependent on that deformation, refreezing, and the dissipation of turbulent and sensible heat energy. We find moulin geometry is responsive to changes in these parameters over the course of hours to days, indicating that diurnal and multi-day variations in melt can substantially alter the geometry of a moulin and, consequently, the pressure-discharge relationship at the bed of the ice sheet. These results should be considered carefully when determining inputs for subglacial hydrologic models. To this end, future work includes combining a parameter space study of these results with an analytic model to create a predictive, stochastic model of moulin and crevasse locations applicable to constraining the potential for surface-to-bed connections in regions where moulin and crevasse locations are unknown and at high elevations under warming atmospheric conditions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C12A..04A
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0726 Ice sheets;
- CRYOSPHERE;
- 0730 Ice streams;
- CRYOSPHERE;
- 0776 Glaciology;
- CRYOSPHERE