Reverse glacier motion during iceberg calving and the cause of glacial earthquakes

Nearly half of Greenland's mass loss occurs through iceberg calving, but the physical mechanisms operating during calving are poorly known and in situ observations are sparse. We show that calving at Greenland's Helheim Glacier causes a minutes-long reversal of the glacier's horizonta...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2015-07, Vol.349 (6245), p.305-308
Main Authors: Murray, T., Nettles, M., Selmes, N., Cathles, L. M., Burton, J. C., James, T. D., Edwards, S., Martin, I., O'Farrell, T., Aspey, R., Rutt, I., Baugé, T.
Format: Article
Language:English
Subjects:
Acceleration
Deflection
Earthquakes
Glaciers
Ice sheets
Icebergs
Motion
Pressure drop
Remote sensing
Seismic phenomena
Seismology
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Summary:Nearly half of Greenland's mass loss occurs through iceberg calving, but the physical mechanisms operating during calving are poorly known and in situ observations are sparse. We show that calving at Greenland's Helheim Glacier causes a minutes-long reversal of the glacier's horizontal flow and a downward deflection of its terminus. The reverse motion results from the horizontal force caused by iceberg capsize and acceleration away from the glacier front. The downward motion results from a hydrodynamic pressure drop behind the capsizing berg, which also causes an upward force on the solid Earth. These forces are the source of glacial earthquakes, globally detectable seismic events whose proper interpretation will allow remote sensing of calving processes occurring at increasing numbers of outlet glaciers in Greenland and Antarctica.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.aab0460