Glacier movement: a highly studied indicator of global warming

Glacier movement : a highly studied indicator of global warming

Mountain glaciers are excellent indicators of climate variations at global level. Monitoring ten sites located around the world, the French observatory GLACIOCLIM analyses glacier sensitivity. The resulting observations and studies look at glacier surface mass balances, as well as other factors such as glacier velocity, length, volume and internal temperature. Producing a glacier mass balance involves calculating all processes that either add mass to a glacier, like snowfall, or remove mass, like melting. 

The thermal regime of a glacier influences its dynamics: if the base is at a negative temperature, the glacier does not slide on its bed and its flow is limited to ice deformation. However, if the glacier is temperate (close to its melting point), it slides on its rocky bed and its sliding velocity is determined by water pressure at the base.

The Mont Blanc massif : a pilot site for modelling

Studies carried out by the Institute of Environmental Geosciences at Université Grenoble Alpes on glacial areas in the Alps at an altitude of more than 3800 metres mainly concern the Col du Dôme glacier in the Mont Blanc massif at 4250 m. At these altitudes, the ice is said to be “cold”, which means at a negative temperature throughout the ice column and down to the base. Local measurements of temperature, radiation, humidity and wind have been made using a meteorological station located on the site. Work carried out since 1993 has revealed the distribution of snow accumulation and temperature variations through the glacier’s entire depth at three separate drilling sites. Thanks to data collected from the drills (temperature and density), monitoring of a network of stakes on the surface (measurement of the field of velocity and accumulation), and detailed analysis of exchange processes between the atmosphere and the glacier, it has been possible to build a thermo-mechanical model for three-dimensional simulation of the thermal regime of the Col du Dôme, where, at a depth of 50 m, ice-warming of 3°C has been observed between 1994 and 2021.

More generally speaking, Alpine glaciers have lost an average of 40 cm in ice thickness per year over the course of the twentieth century and, in the last two decades, they have been losing an average of 1.3 m per year.