Seismicity on the western Greenland Ice Sheet : surface fracture in the vicinity of active moulins
Carmichael, Joshua D.
Behn, Mark D.
Das, Sarah B.
King, Matt A.
Stevens, Laura A.
MetadataShow full item record
KeywordWestern Greenland Ice Sheet; Icequakes; Statistical signal processing; GPS; Supraglacial lakes; Seismic threshold monitoring
We analyzed geophone and GPS measurements collected within the ablation zone of the western Greenland Ice Sheet during a ~35 day period of the 2011 melt season to study changes in ice deformation before, during, and after a supraglacial lake drainage event. During rapid lake drainage, ice flow speeds increased to ~400% of winter values, and icequake activity peaked. At times >7 days after drainage, this seismicity developed variability over both diurnal and longer periods (~10 days), while coincident ice speeds fell to ~150% of winter values and showed nightly peaks in spatial variability. Approximately 95% of all detected seismicity in the lake basin and its immediate vicinity was triggered by fracture propagation within near-surface ice (<330 m deep) that generated Rayleigh waves. Icequakes occurring before and during drainage frequently were collocated with the down flow (west) end of the primary hydrofracture through which the lake drained but shifted farther west and outside the lake basin after the drainage. We interpret these results to reveal vertical hydrofracture opening and local uplift during the drainage, followed by enhanced seismicity and ice flow on the downstream side of the lake basin. This region collocates with interferometric synthetic aperture radar-measured speedup in previous years and could reflect the migration path of the meltwater supplied to the bed by the lake. The diurnal seismic signal can be associated with nightly reductions in surface melt input that increase effective basal pressure and traction, thereby promoting elevated strain in the surficial ice.
Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Earth Surface 120 (2015): 1082–1106, doi:10.1002/2014JF003398.
Suggested CitationJournal of Geophysical Research: Earth Surface 120 (2015): 1082–1106
Showing items related by title, author, creator and subject.
DeFoor, Whitney; Person, Mark; Larsen, Hans Christian; Lizarralde, Daniel; Cohen, Denis; Dugan, Brandon (American Geophysical Union, 2011-07-28)Isotopically light (−1‰ to −8‰ δ18O) and fresh pore fluids (300–520 mM Cl−) were found in continental shelf sediments up to 100 km offshore of southeastern (SE) Greenland, suggesting infiltration and mixing of ice sheet ...
Bhatia, Maya P.; Das, Sarah B.; Longnecker, Krista; Charette, Matthew A.; Kujawinski, Elizabeth B. (2010-03-16)Subsurface microbial oxidation of overridden soils and vegetation beneath glaciers and ice sheets may affect global carbon budgets on glacial-interglacial timescales. The likelihood and magnitude of this process depends ...
Seasonal and interannual variability in the hydrology and geochemistry of an outlet glacier of the Greenland Ice Sheet Linhoff, Benjamin S. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-02)In the spring and summer within the ablation zone of the Greenland Ice Sheet (GrIS), meltwater drains to the ice sheet bed through an evolving network of efficient channelized and inefficient distributed drainage systems. ...