Ice-front variation and tidewater behavior on Helheim and Kangerdlugssuaq Glaciers, Greenland

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Read Full Article (file size: 456418 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, F01004, doi:10.1029/2007JF000837, 2008 Ice-front variation and tidewater behavior on Helheim and Kangerdlugssuaq Glaciers, Greenland Ian Joughin University of Washington Polar Science Center, Applied Physics Laboratory, Seattle, Washington, USA Ian Howat School of Earth Sciences and Byrd Polar Research Center, The Ohio State University, Columbus, Ohio, USA Richard B. Alley Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania, USA Goran Ekstrom Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, USA Mark Fahnestock Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire, USA Twila Moon University of Washington Polar Science Center, Applied Physics Laboratory, Seattle, Washington, USA Meredith Nettles Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, USA Martin Truffer Geophysical Institute, University of Alaska, Fairbanks, Alaska, USA Victor C. Tsai Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA Abstract We used satellite images to examine the calving behavior of Helheim and Kangerdlugssuaq Glaciers, Greenland, from 2001 to 2006, a period in which they retreated and sped up. These data show that many large iceberg-calving episodes coincided with teleseismically detected glacial earthquakes, suggesting that calving-related processes are the source of the seismicity. For each of several events for which we have observations, the ice front calved back to a large, pre-existing rift. These rifts form where the ice has thinned to near flotation as the ice front retreats down the back side of a bathymetric high, which agrees well with earlier theoretical predictions. In addition to the recent retreat in a period of higher temperatures, analysis of several images shows that Helheim retreated in the 20th Century during a warmer period and then re-advanced during a subsequent cooler period. This apparent sensitivity to warming suggests that higher temperatures may promote an initial retreat off a bathymetric high that is then sustained by tidewater dynamics as the ice front retreats into deeper water. The cycle of frontal advance and retreat in less than a century indicates that tidewater glaciers in Greenland can advance rapidly. Greenland's larger reservoir of inland ice and conditions that favor the formation of ice shelves likely contribute to the rapid rates of advance. Received 23 May 2007; accepted 23 October 2007; published 26 January 2008. Keywords: Glaciology; Greenland; ice sheet. Index Terms: 0720 Cryosphere: Glaciers; 0776 Cryosphere: Glaciology (1621, 1827, 1863); 0726 Cryosphere: Ice sheets; 0732 Cryosphere: Icebergs. Read Full Article (file size: 456418 bytes) Cited by Citation: Joughin, I., I. Howat, R. B. Alley, G. Ekstrom, M. Fahnestock, T. Moon, M. Nettles, M. Truffer, and V. C. Tsai (2008), Ice-front variation and tidewater behavior on Helheim and Kangerdlugssuaq Glaciers, Greenland, J. Geophys. Res., 113, F01004, doi:10.1029/2007JF000837. Copyright 2008 by the American Geophysical Union.

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