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Moulin Volumes Regulate Subglacial Water Pressure on the Greenland Ice Sheet
Author(s) -
Covington M. D.,
Gulley J. D.,
Trunz C.,
Mejia J.,
Gadd W.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl088901
Subject(s) - meltwater , geology , water pressure , greenland ice sheet , hydrology (agriculture) , geomorphology , ice sheet , environmental science , oceanography , glacier , geotechnical engineering
Meltwater inputs to moulins regulate Greenland Ice Sheet sliding speeds by controlling water pressure in the most connected regions of the subglacial drainage system. While moulin storage capacities are a critical control on subglacial water pressure, few observations exist to constrain storage. Using direct observations inside moulins, we show that moulin cross‐sectional areas can be at least 500 m 2 , far greater than is observed at the surface or assumed in models. Moulin water level measurements and numerical modeling reveal that diurnal variability in moulin water pressure is highly attenuated in moulins with large storage volumes ( ∼ 3% ice pressure), relative to moulins with smaller storage volumes ( ∼ 25% ice pressure). Because large variability in moulin water pressure is linked to processes that ultimately reduce ice sliding speeds, ice sliding speeds in areas drained by large moulins may be more sensitive to long‐term increases in meltwater than areas drained by small moulins.