3.4 Glacier mass loss
The reduction in the areal extents of the two cirque glaciers within the rock glacier catchment was calculated for the time period 2006 to 2015 (Figure 1b) using the glacier inventories GI3 of Fischer et al. (2015) and GI4 of Buckel and Otto (2018)). The corresponding ice volume loss was estimated based on a thickness-area scaling relation (e.g. Chen & Ohmura, 1990; discussed in Azocar & Brenning, 2010). Assuming a linear trend in volume loss for the 9 years between the two glacier extents, an estimated annual average ice loss was computed. Assuming further an ice density of ~900 kg/m³, the water equivalent lost per year was estimated.
This order of magnitude estimate is used as a plausibility check for the glacier ice melt water contribution of the rainfall-runoff model as no direct information on the runoff from the cirque glaciers is available.