Future high-mountain hydrology: a new parameterization of glacier retreat

摘要

Global warming is expected to significantly affect the runoff regimeof mountainous catchments. Simple methods for calculating futureglacier change in hydrological models are required in order toreliably assess economic impacts of changes in the water cycle overthe next decades. Models for temporal and spatial glacier evolutionneed to describe the climate forcing acting on the glacier, and iceflow dynamics. Flow models, however, demand considerable computationalresources and field data input and are moreover not applicable on theregional scale. Here, we propose a simple parameterization forcalculating the change in glacier surface elevation and area, which ismass conserving and suited for hydrological modelling. The Δh-parameterization is an empirical glacier-specific function derivedfrom observations in the past that can easily be applied to largesamples of glaciers. We compare the Δh-parameterization toresults of a 3-D finite-element ice flow model. As case studies, theevolution of two Alpine glaciers of different size over the period2008–2100 is investigated using regional climate scenarios. Theparameterization closely reproduces the distributed ice thicknesschange, as well as glacier area and length predicted by the ice flowmodel. This indicates that for the purpose of transient runoffforecasts, future glacier geometry change can be approximated using asimple parameterization instead of complex ice flowmodelling. Furthermore, we analyse alpine glacier response to 21stcentury climate change and consequent shifts in the runoff regime of ahighly glacierized catchment using the proposed methods.