Ahlstrøm, A.

Davis, J.

Elosegui, P.

Forsberg, René

Hamilton, G.

Jørgensen, T.

Kahn, S.

Langer, M.

Larsen, T.

Nettles, M.

Rkström, G.

Stearns, L.

Stenseng, Lars

During the summer field season, 2006, we undertook a pilot geophysical experiment at Helheim Glacier, East Greenland, in which we deployed a network of GPS instruments on and around the glacier to measure the ice deformation field as a function of time. The experiment was motivated by the discovery of a new class of earthquakes occurring at glaciers in Alaska, Antarctica, and Greenland (Ekström, Nettles, and Abers, 2003). Teleseismic analysis indicates that these glacial earthquakes may result from the rapid sliding of the glacial ice over the glacier bed, and recent evidence (Ekström, Nettles, and Tsai, 2006) suggests a link to the hydrological cycle. However, little is understood about the mechanism by which the earthquakes occur. We installed sixteen GPS receivers on Helheim glacier, in a network spanning an upglacier distance of ~25~km from a point ~10~km behind the calving front. We also installed three GPS receivers at nearby rock sites to help define a stable reference frame. The stations were deployed in late June, 2006, and retrieved in late August, 2006. The GPS receivers recorded at a rate of at least 5~samples/sec. In addition, we operated several receivers for a few days each just behind the calving front during field visits in late June, late July, and late August, and we recorded the tidal stage using a pressure sensor near the end of Helheim Fjord for ~3~weeks during the experiment. Initial results show a variation in flow speed from about 25~m/day near the calving front to about 6~m/day at a location ~35~km behind the front. The horizontal flow speeds are tidally modulated, and an abrupt spatial change in vertical displacements due to the water tide gives the probable location of the glacier grounding line. We will present our geodetic results, and combine these results with seismological and glaciological observations to place constraints on the conditions under which glacial earthquakes are generated

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Downloaded from orbit.dtu.dk on: Dec 17, 2017Helheim 2006: Integrated Geophysical Observations of Glacier FlowNettles, M.; Ahlstrøm, A.; Elosegui, P.; Hamilton, G.; Kahn, S.; Langer, M.; Stearns, L.; Stenseng, Lars;Davis, J.; Rkström, G.; Forsberg, René; Jørgensen, T.; Larsen, T.Publication date:2006Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Nettles, M., Ahlstrøm, A., Elosegui, P., Hamilton, G., Kahn, S., Langer, M., ... Larsen, T. (2006). Helheim 2006:Integrated Geophysical Observations of Glacier Flow. Abstract from American Geophysical Union Fall Meeting2006, San Francisco,CA, United States.AGU Abstract Browser BetaAboutMeetingsSectionsIndex TermsAdvanced Search Submit QueryHelheim 2006: Integrated Geophysical Observations ofGlacier FlowDetailsMeeting 2006 Fall MeetingSection SeismologySession Bipolar Seismology IIIdentifier S44A-08AuthorsNettles, M*, Lamont-Doherty Earth Observatory, Columbia University, Palisades,NY 10964 United StatesAhlstrøm, A, Geological Survey of Denmark and Greenland, (GEUS), Copenhagen,DK-1350 DenmarkElósegui, P, Institute for Space Sciences, CSIC/IEEE, Barcelona, 08034 SpainHamilton, G, Climate Change Institute, University of Maine, Orono, ME 04469United StatesKhan, S, Danish National Space Center, (DRC), Copenhagen, DK-2100 DenmarkLanger, M, Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY10964 United StatesStearns, L, Climate Change Institute, University of Maine, Orono, ME 04469 UnitedStatesStenseng, L, Danish National Space Center, (DRC), Copenhagen, DK-2100DenmarkDavis, J, Harvard-Smithsonian Center for Astrophysics, Space Geodesy Group,Cambridge, MA 02138 United StatesEkström, G, Lamont-Doherty Earth Observatory, Columbia University, Palisades,NY 10964 United StatesForsberg, R, Danish National Space Center, (DRC), Copenhagen, DK-2100DenmarkJørgensen, T, Geological Survey of Denmark and Greenland, (GEUS), Copenhagen,DK-1350 DenmarkLarsen, T, Geological Survey of Denmark and Greenland, (GEUS), Copenhagen,DK-1350 DenmarkIndexTermsGlaciers [0720]GEODESY AND GRAVITY [1200]Integrations of techniques [1295]AGU Abstract Browser http://abstractsearch.agu.org/meetings/2006/FM/sections/S/se...1 of 2 06/02/14 10:39Abrupt/rapid climate change [1605]Earthquake source observations [7215]AbstractDuring the summer field season, 2006, we undertook a pilot geophysical experiment at HelheimGlacier, East Greenland, in which we deployed a network of GPS instruments on and around theglacier to measure the ice deformation field as a function of time. The experiment was motivatedby the discovery of a new class of earthquakes occurring at glaciers in Alaska, Antarctica, andGreenland (Ekström, Nettles, and Abers, 2003). Teleseismic analysis indicates that these glacialearthquakes may result from the rapid sliding of the glacial ice over the glacier bed, and recentevidence (Ekström, Nettles, and Tsai, 2006) suggests a link to the hydrological cycle. However,little is understood about the mechanism by which the earthquakes occur. We installed sixteenGPS receivers on Helheim glacier, in a network spanning an upglacier distance of ~25~km from apoint ~10~km behind the calving front. We also installed three GPS receivers at nearby rock sitesto help define a stable reference frame. The stations were deployed in late June, 2006, andretrieved in late August, 2006. The GPS receivers recorded at a rate of at least 5~samples/sec. Inaddition, we operated several receivers for a few days each just behind the calving front duringfield visits in late June, late July, and late August, and we recorded the tidal stage using a pressuresensor near the end of Helheim Fjord for ~3~weeks during the experiment. Initial results show avariation in flow speed from about 25~m/day near the calving front to about 6~m/day at a location~35~km behind the front. The horizontal flow speeds are tidally modulated, and an abrupt spatialchange in vertical displacements due to the water tide gives the probable location of the glaciergrounding line. We will present our geodetic results, and combine these results with seismologicaland glaciological observations to place constraints on the conditions under which glacialearthquakes are generated.Cite as: Author(s) (2006), Title, Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstract S44A-08Created by Eric Rozell and Tom Narock. 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Helheim 2006: Integrated Geophysical Observations of Glacier Flow

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Helheim 2006: Integrated Geophysical Observations of Glacier Flow

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