HR: 1340h
AN: C43C-0238    [Abstracts]
TI: Photographic Snow-cover Monitoring on St Sorlin Glacier, France.
AU: * GERBAUX, M
EM: gerbaux@lgge.obs.ujf-grenoble.fr
AF: LGGE UJF/CNRS, 54, rue MoliŠre -DU BP 96, St. MARTIN d'HERES, 38402 France, Metropolitan
AU: Genthon, C
EM: genthon@lgge.obs.ujf-grenoble.fr
AF: LGGE UJF/CNRS, 54, rue MoliŠre -DU BP 96, St. MARTIN d'HERES, 38402 France, Metropolitan
AU: Dedieu, J
EM: Dedieu@lgge.obs.ujf-grenoble.fr
AF: LGGE UJF/CNRS, 54, rue MoliŠre -DU BP 96, St. MARTIN d'HERES, 38402 France, Metropolitan
AU: Balestrieri, J
EM: Balestrieri@lgge.obs.ujf-grenoble.fr
AF: LGGE UJF/CNRS, 54, rue MoliŠre -DU BP 96, St. MARTIN d'HERES, 38402 France, Metropolitan
AB: Like most other glaciers in the Alps, the St Sorlin glacier (french Alps, 45.16řN, 6.16řE, 2900 m asl mean elevation and 3km2 of surface area) has been retreating fast in the last 20 years. To understand the meteorological factors responsible for this retreat, and to tentatively predict glaciers evolution in a changing (warming) climate, we use a distributed snow/ice mass and energy balance model derived from the CROCUS snow model (M‚t‚o-France). There is no direct meteorological observation on or near St Sorlin glacier yet, and hourly meteorology to force the snow/ice model is obtained from disaggregated meteorological analyses. The model is found to reproduce the St Sorlin mass balance of the last 20 years as obtained from field glaciological measurements and stereophotographic reconstructions. The model is also found to reproduce the interannual variations of the equilibrium line as determined from optical satellite imagery. Because of the albedo feedback involved, it is also important to verify that the summer snow/ice transition on the glacier is correctly simulated. Thus, an automated photographic system was set up facing St Sorlin glacier to monitor the evolution of the snow cover. The system was installed on the 13th of July 2004 and is still in operation at time of abstract writing. Digital photographies are taken every 4 hours, permitting so far at least one non-obstructed (rain, fog) picture per day. The first pictures in the series show an almost fully snow-covered glacier while the latest ones show bare ice up to the highest parts of the glacier. Snow is occasionally deposited during precipitation events but hardly last more than 3 days. Snow line position is deduced from pictures using a DEM with georeferenced points visible on pictures. It should then be compared with the modelled one. The automated photographic system provides not only snow cover to check snow/ice model results at seasonal time-scales, but also qualitative meteorological information (precipitation, cloud cover, fog) that may also help verify some aspects of the disaggregated meteorology in input of the model.
UR: http://www-lgge.ujf-grenoble.fr/equipes/glaciers/DonneesDisp/ServiceObs/home.shtml
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting