HR: 11:50h
AN: G42A-07    [Abstracts]
TI: Glacial surges flex the crust of the Earth: Crustal deformation associated with rapid ice flow and mass redistribution at Icelandic outlet glaciers observed by InSAR
AU: * Sigmundsson, F
EM: fs@hi.is
AF: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Reykjavik, IS-101 Iceland
AU: Pedersen, R
EM: rikke@hi.is
AF: Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Reykjavik, IS-101 Iceland
AU: Feigl, K L
EM: feigl@dtp.obs-mip.fr
AF: CNRS/DTP, 14 ave. E. Belin, France, 31400 France
AU: Pinel, V
EM: Virginie.Pinel@univ-savoie.fr
AF: LGIT-Universite de Savoie, Campus Scientifique, Le Bourget du Lac, 73376 France
AU: Bjornsson, H
EM: hb@raunvis.hi.is
AF: Institute of Earth Sciences, University of Iceland, Reykjavik, IS-101 Iceland
AB: Mass redistribution on the surface of the Earth may induce deformation and flexure at the site of loading. Glaciers in Iceland are generally decreasing because of warmer climate, resulting in uplift over large areas next to the ice caps at a rate of 1-2 cm/yr. However, this general uplift may be interrupted by sudden subsidence next to ice caps. Instability in ice flow at outlet glaciers can cause sudden glacial surges, when large volumes of ice flow from accumulation areas on the ice caps towards their edges. InSAR observations have revealed subsidence associated with such glacial surges. The most pronounced of these is deformation associated with a glacial surge at the Sidujokull outlet glacier, SW Iceland. A glacial surge in 1994 was associated with a shift of 8.5 cubic km of ice from the accumulation area, towards the outlet areas, with a thickening of the ice front of over 50 m along a more than 20 km long circular edge of this outlet glacier. The ice advance amounted to more than 1 km over an interval of four months. Interferometric analysis of synthetic aperture radar images (InSAR) clearly reveal deformation associated with this mass redistribution. Subsidence of up to several centimeters (more than one interferometric fringe) is observed in about 20 km wide area next the ice edge. The deformation signal gradually recovers in the years after its formation, as the ice mass readjusts after the surge. The observed deformation is evaluated against an elastic deformation model. A map of inferred mass redistribution during the glacial surge is convolved with a Green's function, giving vertical displacement due to a unit point mass applied on an elastic half-space. The resulting displacement scales inversely with E, the Young's modulus of the underlying crust. The value of E can consequently be estimated from the comparison of the observations and model predictions.
DE: 0720 Glaciers
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1243 Space geodetic surveys
DE: 8159 Rheology: crust and lithosphere (8031)
DE: 8160 Rheology: general (1236, 8032)
SC: Geodesy [G]
MN: Fall Meeting 2005