HR: 1340h
AN: C23A-0976    [Abstracts]
TI: Rapid thinning of Mont Blanc glaciers (Alps) derived from satellite images
AU: Arnaud, Y
EM: yves.arnaud@ird.fr
AF: GREAT ICE (IRD), 54 Rue Moliere, BP 96, St Martin d'Heres, 38402 France
AU: * Berthier, E
EM: etienne.berthier@cnes.fr
AF: LEGOS, 18 av. Ed. Belin, Toulouse, 31401 France
AU: Baratoux, D
EM: david.baratoux@cnes.fr
AF: LDTP, 18 av. Ed. Belin, Toulouse, 31401 France
AU: Vincent, C
EM: vincent@lgge.obs.ujf-grenoble.fr
AF: LGGE, 54 Rue Moliere, BP 96, St Martin d'Heres, 38402 France
AU: Remy, F
EM: remy@pinot.legos.cnes.fr
AF: LEGOS, 18 av. Ed. Belin, Toulouse, 31401 France
AB: Mountain glaciers are good indicators of climate change: their mass balance is directly connected to the interannual variability of climatic parameters such as temperature and precipitations. Mass balance is also the key parameter to estimate the contribution of glaciers to sea level rise. A first step toward the measurement of glacier mass balance from space is an accurate measurement of glacier elevation changes. In this study, we measured from satellite images the rapid thinning of glaciers in the French Alps. From pairs of satellite images, we compute Digital Elevation Models (DEMs) for the Mont Blanc area in 1979, 1994, 2000, and 2003. To register the DEMs to the 2003 reference DEM, we adjust their longitude, latitude and altitude over motionless areas. Substracting the DEMs yields the thickness change of glaciers. Inconsistent values are removed assuming a log-normal distribution of our measurements. The uncertainty of the thickness change measurement is greatly reduced by averaging over areas covering altitude intervals of 50 m. Comparisons with topographic profiles and a differential DEM from aerial photographs obtained on the Mer de Glace indicate an overall accuracy of 1m. Below 2100 m, satellite DEMs show an evolution of the thinning rate from 1ñ0.4 m/a (years 1979-1994) to 4.1ñ1.7 m/a (2000-2003). Our methodology provides a complete view of elevation changes of glaciers during the last 25 years. We discuss how the slope and orientation of glaciers control their shrinkage. We also present a first attempt to derive the cumulated mass balance for the Mer de Glace and Argentiere glaciers over the 1979-2003 period. In the near future, applying our method to satellite optical images with meter or sub-meter resolution could monitor the thickness change of remote glaciers with a precision of the order of 10 cm.
DE: 1827 Glaciology (1863)
DE: 1884 Water supply
DE: 1224 Photogrammetry
DE: 1640 Remote sensing
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting