We have reconstructed the annual balance of the Vadret da Morteratsch, Engadine, with a two-dimensional energy-balance model for the period between 1865 and 2005. The model takes into account a parameterisation of the surface energy fluxes, an albedo that decreases exponentially with snow depth as well as the shading effect of the surrounding mountains. The model was first calibrated with a 5-year record of annual balance measurements made at 20 different sites on the glacier between 2001 and 2006 using meteorological data from surrounding weather stations as input. To force the model for the period starting in 1865 we employed monthly temperature and precipitation records from nearby valley stations. The model is capable to reproduce the observed annual balance reasonably well, except for the lower part during the warmest years. Most crucial to the results is the altitudinal precipitation gradient, but this factor is hard to quantify from the limited precipitation data at high elevations. The simulation shows an almost continuous mass loss since 1865, with short interruptions around 1920, 1935 and 1980. A trend towards a more negative annual balance can be observed since the beginning of the 1980s. The simulated cumulative mass balance for the entire period from 1865 to 2005 was found to be -46 m w.e.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > MAR1-Decadal Variability and Global Change