HR: 1340h
AN: PP33B-1282    [Abstracts]
TI: Slow Vertical Downwasting of Cold-Based Ice Sheets in the Rondane Area, Central Scandinavia
AU: * Dahl, S
EM: Svein.Dahl@geog.uib.no
AF: Department of Geography, University of Bergen and Bjerknes Centre for Climate Research, Fosswinckelsgt. 6, Bergen, N-5007, Norway
AU: Linge, H
EM: Henriette.Linge@geo.uib.no
AF: Bjerknes Centre for Climate Research, Allégt. 55, Bergen, N-5007, Norway
AU: Fabel, D
EM: Derek.Fabel@ges.gla.ac.uk
AF: Department of Geographical and Earth Sciences, University of Glasgow, East Quadrangle, Main Building, Glasgow, G12 8QQ, United Kingdom
AU: Murray, A
EM: Andrew.Murray@risoe.dk
AF: Nordic Laboratory for Luminescence Dating, Department of Earth Sciences, Aarhus University and Riso National Laboratory, P.O. Box 59, Roskilde, DK-4000, Denmark
AB: The rate of ice-sheet downwasting following the Late Weichselian glacial maximum (LGM) c. 20 ka is crucial for estimating the vertical extent prior to and during the last deglaciation in central Scandinavia. The Scandinavian Ice Sheet was cold-based in this region, and air temperature is suggested to be the critical factor influencing the rate of downwasting until the final deglaciation took place close to 10 ka. Depending on when the deglaciation started, the rate of downwasting necessary to explain recent ‘maximum' and ‘minimum' estimates for ice-sheet thickness may differ by 1-2 orders of magnitude. Here we present figures for the rate of downwasting based on OSL-dated waterlain sediments exposed to daylight prior to deposition and 10Be exposure dates on erratic boulders and lateral meltwater channels cut into bedrock in different altitudes. The results indicate a very slow vertical downwasting until c. 15 ka, and a somewhat increase prior to c. 13 ka. After a stillstand related to the Younger Dryas (12.8-11.5 ka) the downwasting accelerated until all ice was gone close to 10 ka. The ice-sheet surface was locally lowered c. 120 m from the LGM to 13.8 ka, or about 2.4 cm/year on an average. The results imply that a much thinner continental ice sheet that hitherto suggested by ice-sheet modelling is necessary to explain field observations related to the last deglaciation in the Rondane area.
DE: 0720 Glaciers
DE: 1105 Quaternary geochronology
DE: 1150 Cosmogenic-nuclide exposure dating (4918)
DE: 1621 Cryospheric change (0776)
DE: 1637 Regional climate change
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting