HR: 1340h
AN: C23A-1159    [Abstracts]
TI: Rapid Changes in Outlet Glacier Dynamics in Greenland: Implications for Ice Sheet Mass Balance and Sea Level Rise Scenarios
AU: * Hamilton, G S
EM: gordon.hamilton@maine.edu
AF: Climate Change Institute, University of Maine, 303 Bryand Global Sciences Ctr, Orono, ME 04469 United States
AU: Stearns, L A
EM: leigh.stearns@maine.edu
AF: Climate Change Institute, University of Maine, 303 Bryand Global Sciences Ctr, Orono, ME 04469 United States
AB: Large fast-flowing outlet glaciers are efficient conduits for the transport of mass from an ice sheet interior to the ocean. In Greenland, calving from outlet glaciers accounts for about half the mass loss from the ice sheet, with most of the remainder coming from runoff and evaporation/sublimation of surface melt. Changes in the flow dynamics of these glaciers will have significant impacts on ice sheet mass balance and sea level. However, most model predictions for future mass balance and sea level rise scenarios consider only centennial-millennial scale changes in ice dynamics. The basis for these predictions might be in error, based on new studies of outlet glacier dynamics in East Greenland. Our study focuses on five large outlet glaciers on Greenland's east coast, between 66-72 degrees north. Historical flow patterns for each glacier are reconstructed from archival field measurements or satellite remote sensing analyses and compared with velocity measurements obtained using GPS methods in summer 2005. We find that the three northernmost glaciers (Daugaard Jensen, Graah, and Vestfjord glaciers) are moving at speeds consistent with earlier determinations based on data collected in 1968 and 2001. However, large changes in flow speed are observed on the two southernmost glaciers (Kangerdlugssuaq and Helheim glaciers). Both glaciers have accelerated; from ~5 km/yr to ~14 km/yr (Kangerdlugssuaq); and ~8 km/yr to ~12 km/yr (Helheim). Our analysis indicates that the accelerations occurred rapidly, perhaps in the 1-2 years prior to our field measurements. We hypothesize that the southern glaciers are responding to a common triggering mechanism and, further, that the same mechanism is not yet operating farther north. The likely trigger is enhanced melt water production due to recent climate warming which facilitates basal sliding. Increased summer melting has been observed in SE Greenland, but is not as extensive near the northern glaciers. One implication of our work is that as climate warming migrates north, other large outlet glaciers will exhibit similar rapid ice dynamics responses as Kangerdlugssuaq and Helheim glaciers. If correct, this hypothesis implies a larger and faster Greenland ice sheet contribution to sea level rise than is predicted by current models.
DE: 0700 CRYOSPHERE (4540)
DE: 0726 Ice sheets
DE: 0758 Remote sensing
DE: 1621 Cryospheric change (0776)
DE: 9315 Arctic region (0718, 4207)
SC: Cryosphere [C]
MN: Fall Meeting 2005