title: Ice sheets. Reverse glacier motion during iceberg calving and the cause of glacial earthquakes.
abstract: 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.
authors.affiliation: Glaciology Group, Department of Geography, College of Science, Swansea University, Swansea SA2 8PP, UK.
authors.forename: T
authors.initials: T
authors.lastname: Murray
authors.affiliation: Lamont-Doherty Earth Observatory, Columbia University, New York, NY 10964, USA.
authors.forename: M
authors.initials: M
authors.lastname: Nettles
authors.affiliation: Glaciology Group, Department of Geography, College of Science, Swansea University, Swansea SA2 8PP, UK.
authors.forename: N
authors.initials: N
authors.lastname: Selmes
authors.affiliation: Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Cathles
authors.affiliation: Department of Physics, Emory University, Atlanta, GA 30322, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Burton
authors.affiliation: Glaciology Group, Department of Geography, College of Science, Swansea University, Swansea SA2 8PP, UK.
authors.forename: T D
authors.initials: TD
authors.lastname: James
authors.affiliation: School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: S
authors.initials: S
authors.lastname: Edwards
authors.affiliation: School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: I
authors.initials: I
authors.lastname: Martin
authors.affiliation: Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD, UK.
authors.forename: T
authors.initials: T
authors.lastname: O'Farrell
authors.affiliation: Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD, UK.
authors.forename: R
authors.initials: R
authors.lastname: Aspey
authors.affiliation: Glaciology Group, Department of Geography, College of Science, Swansea University, Swansea SA2 8PP, UK.
authors.forename: I
authors.initials: I
authors.lastname: Rutt
authors.affiliation: Thales UK, Research and Technology, Worton Drive, Reading, Berkshire RG2 0SB, UK.
authors.forename: T
authors.initials: T
authors.lastname: Baugé