Seasonal Speedup Along the Western Flank of the Greenland Ice Sheet

It has been widely hypothesized that a warmer climate in Greenland would increase the volume of lubricating surface meltwater reaching the ice-bedrock interface, accelerating ice flow and increasing mass loss. We have assembled a data set that provides a synoptic-scale view, spanning ice-sheet to outlet-glacier flow, with which to evaluate this hypothesis. On the ice sheet, these data reveal summer speedups (50 to 100%) consistent with, but somewhat larger than, earlier observations. The relative speedup of outlet glaciers, however, is far smaller (<15%). Furthermore, the dominant seasonal influence on Jakobshavn Isbrae's flow is the calving front's annual advance and retreat. With other effects producing outlet-glacier speedups an order of magnitude larger, seasonal melt's influence on ice flow is likely confined to those regions dominated by ice-sheet flow.

[1]  W. Haeberli,et al.  The Uplift of Unteraargletscher at the Beginning of the Melt Season—A Consequence of Water Storage at the Bed? , 1983, Journal of Glaciology.

[2]  R. Armstrong,et al.  The Physics of Glaciers , 1981 .

[3]  A. Iken.  The effect of the subglacial water pressure on the sliding velocity of a glacier in an idealized numerical model , 1981 .

[4]  R. Bindschadler,et al.  Combined measurements of subglacial water pressure and surface velocity of Findelengletscher, Switzerland: conclusions about drainage system and sliding mechanism , 1986 .

[5]  W. Harrison,et al.  Jakobshavns Isbræ, West Greenland: seasonal variations in velocity -- or lack thereof , 1990 .

[6]  Mark F. Meier,et al.  Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier. 1: Observations , 1994 .

[7]  Ron Kwok,et al.  A Mini-Surge on the Ryder Glacier, Greenland, Observed by Satellite Radar Interferometry , 1996, Science.

[8]  Kenneth C. Jezek,et al.  Jakobshavn Glacier, west Greenland: 30 years of spaceborne observations , 1998 .

[9]  Konrad Steffen,et al.  Surface Melt-Induced Acceleration of Greenland Ice-Sheet Flow , 2002, Science.

[10]  Konrad Steffen,et al.  Investigation of surface melting and dynamic thinning on Jakobshavn Isbrae, Greenland , 2003 .

[11]  Richard B. Alley,et al.  Implications of increased Greenland surface melt under global-warming scenarios: ice-sheet simulations , 2004 .

[12]  Ian Joughin,et al.  Large fluctuations in speed on Greenland's Jakobshavn Isbræ glacier , 2004, Nature.

[13]  Tavi Murray,et al.  Seasonal variation in velocity before retreat of Jakobshavn Isbræ, Greenland , 2005 .

[14]  Ian M. Howat,et al.  Rapid retreat and acceleration of Helheim Glacier, east Greenland , 2005 .

[15]  Sheng-Hung Wang,et al.  Greenland Ice Sheet Surface Mass Balance Variability (1988–2004) from Calibrated Polar MM5 Output* , 2006 .

[16]  A. Gore.  An Inconvenient Truth: The Planetary Emergency of Global Warming and What We Can Do About It , 2006 .

[17]  Tavi Murray,et al.  Rapid and synchronous ice‐dynamic changes in East Greenland , 2006 .

[18]  E. Rignot,et al.  Changes in the Velocity Structure of the Greenland Ice Sheet , 2006, Science.

[19]  M. Dubey,et al.  Greenland warming of 1920–1930 and 1995–2005 , 2006 .

[20]  W. T. Pfeffer,et al.  Two modes of accelerated glacier sliding related to water , 2007 .

[21]  T. Scambos,et al.  Rapid Changes in Ice Discharge from Greenland Outlet Glaciers , 2007, Science.

[22]  H. L. Miller,et al.  Climate Change 2007: The Physical Science Basis , 2007 .

[23]  Ian Joughin,et al.  Fracture Propagation to the Base of the Greenland Ice Sheet During Supraglacial Lake Drainage , 2008, Science.