Probabilistic estimation of glacier volume and glacier bed topography: the Andean glacier Huayna West

Abstract. Glacier retreat will increase sea level and decrease fresh water availability. Glacier retreat will also induce morphologic and hydrologic changes due to the formation of glacial lakes. Hence, it is important not only to estimate glacier volume, but also to understand the spatial distribution of ice thickness. There are several approaches for estimating glacier volume and glacier thickness. However, it is not possible to select an optimal approach that works for all locations. It is important to analyse the relation between the different glacier volume estimations and to provide confidence intervals of a given solution. The present study presents a probabilistic approach for estimating glacier volume and its confidence interval. Glacier volume of the Andean glacier Huayna West was estimated according to different scaling relations. Besides, glacier volume and glacier thickness were estimated assuming plastic behaviour. The present study also analysed the influence of considering a variable glacier density due to ice firn densification. It was found that the different estimations are described by a lognormal probability distribution. Considering a confidence level of 90%, the estimated glacier volume is 0.0275 km³ ± 0.0052 km³. Considering a confidence level of 90%, the estimated glacier thickness is 24.98 m with a confidence of ±4.67 m. The mean basal shear stress considering plastic behaviour is 82.5 kPa. The reconstruction of glacier bed topography showed the future formation of a glacier lake with a maximum depth of 32 m.