Geophys. Res. Lett., 35 (2008) L24503; doi:10.1029/2008GL036127.

Step-wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland

M. Nettles (Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA), T. B. Larsen (Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark), P. Elósegui (Institute for Space Sciences, CSIC, IEEC, Barcelona, Spain), G. S. Hamilton, L. A. Stearns (Climate Change Institute, University of Maine, Orono, ME, USA), A. P. Ahlstrøm (Geological Survey of Denmark and Greenland, Copenhagen, Denmark), J. L. Davis (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA), M. L. Andersen (Geological Survey of Denmark and Greenland, Copenhagen, Denmark), J. de Juan (Institute for Space Sciences, CSIC, IEEC, Barcelona, Spain), S. A. Khan, L. Stenseng (Danish National Space Center, Copenhagen, Denmark), G. Ekström (Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA), and R. Forsberg (Danish National Space Center, Copenhagen, Denmark)

Abstract

Geodetic observations show several large, sudden increases in flow speed at Helheim Glacier, one of Greenland's largest outlet glaciers, during summer, 2007. These step-like accelerations, detected along the length of the glacier, coincide with teleseismically detected glacial earthquakes and major iceberg calving events. No coseismic offset in the position of the glacier surface is observed; instead, modest tsunamis associated with the glacial earthquakes implicate glacier calving in the seismogenic process. Our results link changes in glacier velocity directly to calving-front behavior at Greenland's largest outlet glaciers, on timescales as short as minutes to hours, and clarify the mechanism by which glacial earthquakes occur.