HR: 08:45h
AN: C41A-04    [Abstracts]
TI: Dramatic Changes in the Flow Velocity of Helheim Glacier, SE Greenland: a Result of Climate Forcing?
AU: * de Lange, R
EM: geordl@leeds.ac.uk
AF: School of Geography, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT United Kingdom
AU: * de Lange, R
EM: geordl@leeds.ac.uk
AF: Glaciology Group, School of Environment and Society, Swansea University, Singleton Park, Swansea, SA2 8PP United Kingdom
AU: Murray, T
EM: T.Murray@swansea.ac.uk
AF: Glaciology Group, School of Environment and Society, Swansea University, Singleton Park, Swansea, SA2 8PP United Kingdom
AU: Luckman, A
EM: A.Luckman@swansea.ac.uk
AF: Glaciology Group, School of Environment and Society, Swansea University, Singleton Park, Swansea, SA2 8PP United Kingdom
AU: Hanna, E
EM: E.Hanna@Sheffield.ac.uk
AF: Department of Geography, University of Sheffield, Winter Street, Sheffield, S10 2TN United Kingdom
AB: Outlet glaciers in Southeast Greenland have recently been speeding up dramatically; including Helheim Glacier which accelerated 25% between 2002/2003 in comparison to the late-1990's. During the 1990's NASA observed the margins of the Greenland Ice Sheet have been thinning at rates exceeding that expected from melt. The recent observed speed-up event seems to confirm that dynamic thinning is occurring in this part of Greenland. We investigate the reasons behind the speed-up of Helheim Glacier. For Helheim's drainage basin, monthly modeled climate data, such as temperature, surface runoff and accumulation, are derived from ECMWF reanalyses. These data show that the surface runoff was anomalously high during the years of 1995 and 1998, but not during either 2002 or 2003. The flow velocity of Helheim Glacier, derived from intensity tracking of 35 days repeat pass period ERS SAR data, was 25% higher in 2002/2003 than the rather stable flow during the period of 1995-1998. Throughout this period velocities of up to 20 md^-1 were observed with no consistent seasonal pattern a few kilometres up-glacier from the front. Although observations are sparse, ice velocities within the years of 1992 and 1993 were also similar. Our results show a dramatic increase in velocity during 2002/2003 but none during the 1990's, although thinning rates observed by NASA of around 1.5 ma^-1. If dynamic thinning has been occurring during the 1990's, it happened gradually, or during data gaps which in 1993-1994. These two years were anomalously low melt years, while the flow regime remained robust against the high runoff during 1995 and 1998. The recent speed-up does not coincide with high runoff. Our results suggest no direct link between surface runoff and velocity during the 1990's or the recent speed-up event.
DE: 0720 Glaciers
DE: 0758 Remote sensing
DE: 0774 Dynamics
DE: 1621 Cryospheric change (0776)
SC: Cryosphere [C]
MN: Fall Meeting 2005