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

Abstract

Abstract. Global warming is expected to significantly affect the runoff regime of mountainous catchments. Simple methods for calculating future glacier change in hydrological models are required in order to reliably assess economic impacts of changes in the water cycle over the next decades. Models for temporal and spatial glacier evolution need to describe the climate forcing acting on the glacier, and ice flow dynamics. Flow models, however, demand considerable computational resources and field data input and are moreover not applicable on the regional scale. Here, we propose a simple parameterization for calculating the change in glacier surface elevation and area, which is mass conserving and suited for hydrological modelling. The h-parameterization is an empirical glacier-specific function derived from observations in the past that can easily be applied to large samples of glaciers. We compare the h-parameterization to results of a 3-D finite-element ice flow model. As case studies, the evolution of two Alpine glaciers of different size over the period 2008-2100 is investigated using regional climate scenarios. The parameterization closely reproduces the distributed ice thickness change, as well as glacier area and length predicted by the ice flow model. This indicates that for the purpose of transient runoff forecasts, future glacier geometry change can be approximated using a simple parameterization instead of complex ice flow modelling. Furthermore, we analyse alpine glacier response to 21st century climate change and consequent shifts in the runoff regime of a highly glacierized catchment using the proposed methods.

An investigation of the thermomechanical features of Laohugou Glacier No. 12 on Qilian Shan, western China, using a two-dimensional first-order flow-band ice flow model

“…The storage of water in glaciers is an important component of the hydrological cycle at different time scales (Jansson et al, 2003;Huss et al, 2010), especially in arid and semiarid regions such as northwestern China, where many glaciers are currently retreating and disappearing (Yao et al, 2012;Neckel et al, 2014;Tian et al, 2014). Located on the northeastern edge of the Tibetan Plateau (36-39 • N, 94-104 • E), Qilian Shan (QS) develops 2051 glaciers covering an area of approximately 1057 km 2 with a total ice volume of approximately 51 km 3 (Guo et al, 2014(Guo et al, , 2015.…”

Glacio-hydrological melt and runoff modelling: a limits of acceptability framework for model selection

“…Excess soil moisture, rainfall and melt are then routed to the catchment outlet via a semi-distributed network of linear-reservoir cascades which represent the water storage and release characteristics of the major hydrological pathways in the watershed. The GHM also simulates the evolution of the glacier geometry under periods 5 of sustained negative mass balance using the ∆-h parametrisation of glacier retreat which has shown to closely reproduce the evolution of Alpine glaciers with results comparable to more complex 3-D finite-element ice flow models (Huss et al, 2010;Li et al, 2015;Van Tiel et al, 2017;Duethmann et al, 2016). Details of this and the soil water balance component of the GHM can be found in Appendix A.…”

“…Figure A2 (bottom) shows the fitted ∆h model to the normalised mean elevation change curve. Following Huss et al (2010), the glacier geometry 5 is updated each year by distributing the net glacier mass balance across the glacier according to this relationship.…”

“…The empirical ∆-h parametrisation (Huss et al, 2010) requires the availability of at least two digital elevation models of the glacier separated in time. The difference between the two is used to define the ∆-h polynomial which has the form: where ∆h is the normalised surface elevation, h r is the normalised elevation range and a, b, γ and c are fitted parameters.…”

Hydrologic vulnerability to climate change of the Mandrone glacier (Adamello-Presanella group, Italian Alps)

“…In this analysis the combined effect of both the climate change impact on the mass balance and the resulting morphological adaptation of the glacier is taken into account with a simplified approach, as done for instance by Huss et al [33], who first calculated the change in glacier surface elevation and area through a simple parameterization and then applied an ice-flow model. Considering the additive and multiplicative correction factors listed in Table 2, a linear change of temperature and precipitation over the 2010-2050 and 2050-2090 periods was assumed.…”