Modelling heat flow in a cold, high-altitude glacier: interpretation of measurements from Colle Gnifetti, Swiss Alps

Abstract

AbstractModelling the heat flow in small, cold high-altitude glaciers is important for the interpretation of paleoclimatic data from ice cores. Coupled glacier-flow and heat-flow models are presented that incorporate the densification, heat advection and possible phase transitions at the permafrost boundaries within the bedrock. Marked bends observed in the temperature profiles from two recent boreholes on Colle Gnifetti, Swiss Alps, are interpreted with the help of a transient heat-flow model, driven with a temperature history. The conclusion is that substantial warming of the mean firn temperature at shallow depths has taken place over the last few decades. This has not been observed before in cold-firn regions of the Alps. Modelled heat fluxes in the Monte Rosa massif are strongly influenced by the mountain topography. This leads to a spatial variability of the temperature gradient near the glacier base which has been observed in boreholes to the bedrock. In order to match the measured temperature profiles in the glacier, the vertical heat flux at great depth must be set to an extremely low value. It is shown with the help of the transient heat-flow model that this is a paleoclimatic effect, possibly enhanced by a degrading permafrost base.