What Can We Learn from Comparing Glacio-Hydrological Models?

Elena Stoll,Johannes Schöber,Johanna Nemec,Felix Oesterle,Florian Hanzer,Matthias Huttenlau,Kristian Förster

doi:10.3390/atmos11090981

Abstract

Glacio-hydrological models combine both glacier and catchment hydrology modeling and are used to assess the hydrological response of high-mountain glacierized catchments to climate change. To capture the uncertainties from these model combinations, it is essential to compare the outcomes of several model entities forced with the same climate projections. For the first time, we compare the results of two completely independent glacio-hydrological models: (i) HQsim-GEM and (ii) AMUNDSEN. In contrast to prevailing studies, we use distinct glacier models and glacier initialization times. At first glance, the results achieved for future glacier states and hydrological characteristics in the Rofenache catchment in Ötztal Alps (Austria) appear to be similar and consistent, but a closer look reveals clear differences. What can be learned from this study is that low-complexity models can achieve higher accuracy in the calibration period. This is advantageous especially when data availability is weak, and priority is given to efficient computation time. Furthermore, the time and method of glacier initialization play an important role due to different data requirements. In essence, it is not possible to make conclusions about the model performance outside of the calibration period or more specifically in the future. Hence, similar to climate modeling, we suggest considering different modeling approaches when assessing future catchment discharge or glacier evolution. Especially when transferring the results to stakeholders, it is vital to transparently communicate the bandwidth of future states that come with all model results.

Highlights

Future high-mountain hydrology is heavily dependent on glacier evolution
For the first time we compare the results of two independent, completely different glacio-hydrological models that are based on separate glacier models
What can be learned from this study is that low-complexity models can achieve higher accuracy at least in the calibration period

Summary

Introduction

Future high-mountain hydrology is heavily dependent on glacier evolution (i.e., the changes of glacier characteristics over time, such as volume, elevation or length). The ongoing climate-induced mass loss of mountain glaciers affects the hydrological cycle on multiple scales [1]. In this context, glacio-hydrological modeling, the combined modeling of both glaciers and catchment hydrology, Atmosphere 2020, 11, 981; doi:10.3390/atmos11090981 www.mdpi.com/journal/atmosphere. The “glacio” component allows changing ice-covered areas to be taken into account when modeling runoff from high-alpine glacierized catchments. There are empirical methods using (i) a volume-area-scaling [9] that estimate the glacier volume based on the glacier area, or (ii) a ∆h approach [10], relating an integrated mass balance to changes in ice thickness (h) and glaciated area. On the other hand, sophisticated state of the art model frameworks, such as the Open Global Glacier Model OGGM [11], comprise “data downloading tools (glacier outlines, topography, climate, validation data), a preprocessing module, a mass-balance model, a distributed ice thickness estimation model, and an ice-flow model” to simulate changes in glacier geometry

Results

Discussion

Conclusion