Self-affine structure of glacial surfaces in Lombardy

The surface of a glacier represents the interface with the atmosphere where mass and energy fluxes exchanges occur due to the exposition to solar radiation, precipitation (solid and liquid) and wind currents. All these factors contribute to the shaping of the glacier surface and of its roughness, in combination with the underlying orography of the bedrock. In this work, we perform a statistical characterisation of the corrugation properties of the surface of glaciers in the Lombardy region of Italy. We show that the surfaces exhibit a self-affine structure characterised by Hurst exponents in the range 0.7 - 1.0. These exponents are significantly larger than the ones of non-glacierised mountain reliefs, which fall in the range 0.5 - 0.7. This indicates that the surface of the glaciers is significantly smoother than the one of the uncovered reliefs. We discuss how several factors can contribute to this result, including the accumulation of snowfall and its redistribution under the action of wind, and the erosion and smoothing of the bedrock substrate determined by the shift of the glacier and by the flow of glacial water.