Subglacial discharge at tidewater glaciers revealed by seismic tremor.
Subglacial discharge influences glacier basal motion and erodes and redeposits sediment. At tidewater glacier termini, discharge drives submarine terminus melting, affects fjord circulation, and is a central component of proglacial marine ecosystems. However, our present inability to track subglacial discharge and its variability significantly hinders our understanding of these processes. Here we report observations of hourly to seasonal variations in 1.5-10 Hz seismic tremor that strongly correlate with subglacial discharge but not with basal motion, weather, or discrete icequakes. Our data demonstrate that vigorous discharge occurs from tidewater glaciers during summer, in spite of fast basal motion that could limit the formation of subglacial conduits, and then abates during winter. Furthermore, tremor observations and a melt model demonstrate that drainage efficiency of tidewater glaciers evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured glacierized environments.
Institute for Geophysics University of Texas at Austin Austin Texas USA.
Timothy C
TC
Bartholomaus
Department of Natural Sciences University of Alaska Southeast Juneau Alaska USA.
Jason M
JM
Amundson
Institute for Geophysics University of Texas at Austin Austin Texas USA.
Jacob I
JI
Walter
Alaska Science Center U.S. Geological Survey Anchorage Alaska USA.
Shad
S
O'Neel
Geophysical Institute University of Alaska Fairbanks Fairbanks Alaska USA.
Michael E
ME
West
Geophysical Institute University of Alaska Fairbanks Fairbanks Alaska USA.
Christopher F
CF
Larsen
glacier hydrology; ice/ocean interactions; seismic tremor; subglacial discharge; submarine melt
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27667869