HR: 08:30h
AN: C41A-03    [Abstracts]
TI: Rapid Changes of Large Tidewater Glaciers in SE Greenland
AU: * Stearns, L A
EM: leigh.stearns@maine.edu
AF: Climate Change Institute, University of Maine, 5790 BGSC, Orono, ME 04469 United States
AU: Hamilton, G S
EM: gordon.hamilton@maine.edu
AF: Climate Change Institute, University of Maine, 5790 BGSC, Orono, ME 04469 United States
AB: New field and satellite remote sensing measurements show that Kangerdlugssuaq Glacier and Helheim Glacier, two fast-flowing tidewater glaciers in South-East Greenland, accelerated 40-300% between 2001 and 2005 and retreated 3-5 km since July 2003. Together, the catchment basins of these two glaciers encompass ~10% of the area of the Greenland ice sheet. Previous studies observed rates of surface lowering on the main trunks of both glaciers that were too large to be caused by enhanced surface melting or decreased snow fall alone. One hypothesis to explain the thinning rates is a change in ice dynamics. We use repeat satellite imagery and published reports to reconstruct the last ~decade of flow histories for both glaciers and compare the results with velocities derived from field GPS surveys in the summer 2005. Helheim Glacier was flowing at ~8 km/yr in 1995 and 2001. In 2005, flow speeds were ~11.7 km/yr, a ~40% increase. The acceleration of Kangerdlugssuaq Glacier was more substantial. Portions of the main trunk that were flowing at ~5 km/yr in 1988, 1996 and 2001 were flowing at ~14 km/yr in summer 2005, an almost threefold increase. The accelerations in flow speeds were accompanied by other changes, including the rapid retreat of calving fronts that had maintained quasi-stable positions for the previous ~40 years, and a lowering of the ice surface by about 100 m, leaving stranded ice on adjacent ridges. The rapid thinning, acceleration and retreat of these two relatively nearby glaciers suggests a common triggering mechanism, such as enhanced surface melting due to regional climate warming. The current flow speeds, ~11 - 14 km/yr at the terminus, are too fast to be caused solely by internal deformation of the ice, implying that an increase in basal sliding forced by additional meltwater production is the probable cause of the velocity increases. The new observations and the hypothesized cause highlight the sensitivity of large outlet glaciers to local climate changes, and have implications for ice sheet mass balance and sea level rise predictions.
DE: 0720 Glaciers
DE: 0726 Ice sheets
DE: 0758 Remote sensing
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: Fall Meeting 2005