Spatial variability in water content at the cold‐temperate transition surface of the polythermal Storglaciären, Sweden

Abstract

The volume fraction of liquid water in temperate glacier ice is important not only for the flow of glaciers and the analysis and processing of ground penetrating radar data from glaciers but also for the stability of the thermal layering in polythermal glaciers. However, little is known about the spatial variations of water content in glaciers. We use relative backscatter strength of ground‐penetrating radar signals to estimate the spatial distribution of water content close to the cold‐temperate transition on Storglaciären, northern Sweden, in an area close to the equilibrium line. The values of relative backscatter strength are calibrated using determinations of absolute water content from temperature measurements across the cold‐temperate transition and the thermodynamic boundary condition at the freezing front. The results show a water content of 0.80%, 0.75%, and 0.58% at three calibration points and a mean water content of 0.8% with a standard deviation of ±0.26% for the extrapolated water content. The extrapolated water content shows a distinct pattern, with lower water content on one side of the glacier center line and higher water content on the other side, with higher water content on the northern side. We hypothesize that the different water contents result from the fact that the ice on either side of the center line originates from different cirques, thus implying spatial variations in the entrapment of water in the firn‐ice transition process in the different cirques.