HR: 0800h
AN: C51B-0280    [Abstracts]
TI: Thermal regime and ice-water content of a glacier in the European Alps using borehole and surface radar
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: Rippin, D
C51B-0280 AF: Faculty of Earth and Environment, University of Leeds, Leeds, LS2 9JT United Kingdom
AU: Barrett, B
C51B-0280 AF: Faculty of Earth and Environment, University of Leeds, Leeds, LS2 9JT United Kingdom
AU: Kilner, M
C51B-0280 AF: Faculty of Earth and Environment, University of Leeds, Leeds, LS2 9JT United Kingdom
AB: The rheology of ice is strongly controlled by its liquid water content: laboratory studies show that a 1% increase in water content increases a sample's strain rate by ~400%. Water content and distribution also have a strong control on radar velocity and attenuation, thus providing a remote technique for assessing ice water content. A suite of surface and borehole radar surveys have been undertaken at the Tsanfleuron Glacier in the European Alps. Common-offset surface radar profiles show that the glacier has a two-layered structure, with the upper layer being characterised by low returned radar power and a lower layer characterised by strong scattering. The thickness of these layers varies rapidly cross glacier and appears to be most strongly controlled by surface topography. Common midpoint and borehole surveys allow estimation of the properties of the two layers. The upper layer appears to consist of cold ice, with a water content ~0.6%, whereas the lower layer is interpreted as containing small water bodies, ~4% by volume. The frequency dependence of scattering in borehole reflection surveys suggests these water bodies are ~0.1 to 0.16 m in diameter, and therefore that the water is unlikely to be stored at crystal grain boundaries. Unexpectedly, this alpine glacier appears to have a polythermal regime, which has important implications for both its hydrology and dynamics.
DE: 0720 Glaciers
DE: 0768 Thermal regime
DE: 0770 Properties
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: Fall Meeting 2005