HR: 0800h
AN: C51A-1023    [Abstracts]
TI: Borehole Logging to Reconstruct Past Annual Accumulation Rates in High Altitude Firn Areas
AU: * Schwerzmann, A A
EM: Aurel.Schwerzmann@ethz.ch
AF: ETH, VAW Glaciology, Gloriastrasse 37, Zurich, 8092 Switzerland
AU: * Schwerzmann, A A
EM: Aurel.Schwerzmann@ethz.ch
AF: ETH, Institute for Atmospheric and Climate Science, Winterthurerstrasse 190, Zurich, 8057 Switzerland
AU: Blatter, H
EM: heinz.blatter@env.ethz.ch
AF: ETH, Institute for Atmospheric and Climate Science, Winterthurerstrasse 190, Zurich, 8057 Switzerland
AU: Funk, M
EM: funk@vaw.baug.ethz.ch
AF: ETH, VAW Glaciology, Gloriastrasse 37, Zurich, 8092 Switzerland
AU: Schwikowski, M
EM: Margit.Schwikowski@psi.ch
AF: Paul Scherrer Institut, Laboratory of Radio and Environmental Chemistry, Villigen PSI, 5232 Switzerland
AB: Our understanding of climatic changes essentially stems from knowledge of past annual accumulation rates. Ice cores give an encrypted review over past precipitation. To decipher the observed layer thickness from ice cores, firn compaction and deformation of annual ice layers have to be taken into account. A new method for measuring the vertical strain-rate was developed which entails the scratching of horizontal grooves directly into the wall of a borehole. No other type of strain markers (disturbing other simultaneous measurements) need to be installed. By tracking the vertical position of these grooves with a caliper probe, the vertical strain-rate including firn compaction can be determined from which the depth-dependent thinning-rate is calculated. In combination with measured annual layer thicknesses, the original accumulation rate can be reconstructed (without resorting to the knowledge of the density profile). Results obtained from an ice core drilling site on Fiescherhorn in the Swiss Alps are compared with model computation.
UR: http://www.glaciology.ch
DE: 1827 Glaciology (1863)
DE: 1854 Precipitation (3354)
DE: 1863 Snow and ice (1827)
DE: 1894 Instruments and techniques
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting