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A Physical Model of Moulin Formation and EvolutionNearly all proglacial water discharge from the present-day 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, including on past ice sheets for which remote-sensing data are not available, 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 the timing of meltwater inputs to the bed. This evolution can impact both the form of the subglacial hydrologic system and the structure of associated geomorphological structures. Here, we develop a physical model of moulin formation and evolution to constrain the role of englacial processes in controlling the form and structure of the subglacial hydrologic system. Ice deformation within and around a moulin is both viscous and elastic, with the rate of turbulent and heat dissipation from water circulation in the moulin controlling both moulin wall melting and warming of the surrounding ice. We find moulin geometry is responsive to changes in these parameters over hours to days, indicating that diurnal and multi-day variations in surface melt can substantially alter the geometry of a moulin and the pressure-discharge relationship at the bed of the ice sheet. These results should be considered carefully when determining surface water inputs for subglacial hydrologic models. In the future, a parameter space study of these results will be combined with an analytic model to create a predictive, stochastic model of moulin and crevasse locations. This future model will be applicable to constraining the potential for surface-to-bed connections in regions where the exact ice-sheet surface morphology is not known, including ice sheets under future warming atmospheric conditions, and paleo ice sheets, where moulins created modern landforms.
Document ID
20190025205
Acquisition Source
Goddard Space Flight Center
Document Type
Poster
Authors
Andrews, Lauren C.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Poinar, Kristin
(Buffalo Univ. NY, United States)
Date Acquired
May 17, 2019
Publication Date
May 12, 2019
Subject Category
Geophysics
Report/Patent Number
GSFC-E-DAA-TN68842
Report Number: GSFC-E-DAA-TN68842
Meeting Information
Meeting: International Glaciological Society Symposium on Glacial Erosion and Sedimentation
Location: Madison, WI
Country: United States
Start Date: May 12, 2019
End Date: May 17, 2019
Sponsors: International Glaciological Society
Distribution Limits
Public
Copyright
Use by or on behalf of the US Gov. Permitted.
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