Historic fluctuations of the Rhone glacier: simulation with a numerical model

Abstract

The Rhone Glacier (Switzerland) is one of the few valley glaciers for which the record of front variations goes back to the beginning of the 17th century. After the neoglacial maximum in the year 1602 there have been notable advances around 1818 and 1856. Since that time the glacier has shown steady retreat with some minor interruptions only. In this contribution we make an attempt to simulate the historical front variations with a numerical glacier model. It is based on the continuity equation for ice mass, applied to the central flowline while taking into account the varying geometry. Both sliding and deformation are related directly to the local driving stress. The gridpoint spacing is 250 m. After a general survey of the basic sensitivity of the Rhone glacier to changes in mass balance and geometry, some climatic series (temperature, precipitation, tree-ring width) were imposed as forcing to the model. A reasonable match of calculated and observed front positions could be obtained, except for the retreat of the last hundred years. To simulate this retreat, an additional 85 m increase of equilibrium-line altitude has to be imposed to the model.