Modeling the Impact of Evolving Moulin Shape on Subglacial Pressure and Conduit Evolution
Abstract
Moulins collect most of the supraglacial meltwater produced on the Greenland ice sheet and directly transfer it to the subglacial drainage system, influencing ice velocities. As such, moulins are important features of the glacial hydrologic system, but their shapes are poorly characterized due to the difficulty in accessing and exploring them. In consequence, moulins are generally assigned a cylindrical geometry in subglacial hydrology models. However, recent field observations show that moulin shapes are complex, likely due to differential melting caused by preferential water paths, as well as vertical variations in ice deformation, elastic opening, and creep closure. The vertical change in moulin diameter may strongly impact diurnal water level oscillation as well as the englacial and subglacial water storage. To investigate the impact of the vertical variation in moulin cross-section on water level dynamics, we develop a single subglacial conduit - moulin model in which we vary the shape of the moulin reservoir. In the model, modified from Schoof (2010), supraglacial meltwater enters the subglacial conduit via a moulin, which is treated as a storage reservoir in which the volume of water is a function of hydraulic head and moulin shape; the subglacial conduit diameter evolves in response to changes in pressure and water discharge via creep closure and ice melting. With this adapted model, we test head fluctuations produced with different moulin geometries to identify how the shape of englacial storage impacts the amplitudes of hydraulic head oscillation and equilibration timescales of the subglacial drainage system. Finally, we show preliminary results of the coupling of an evolving moulin model with the subglacial conduit model, where we explore the dynamics of a subglacial channel with an evolving moulin shape.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C13C1332T
- Keywords:
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- 0720 Glaciers;
- CRYOSPHERE;
- 0726 Ice sheets;
- CRYOSPHERE;
- 0730 Ice streams;
- CRYOSPHERE;
- 0776 Glaciology;
- CRYOSPHERE