Response of snow cover and runoff to climate change in high Alpine catchments of Eastern Switzerland

A model study on the impact of climate change on snow cover and runoff has been conducted for the Swiss Canton of Graubünden. The model Alpine3D has been forced with the data from 35 Automatic Weather Stations in order to investigate snow and runoff dynamics for the current climate. The data set has then been modified to reflect climate change as predicted for the 2021-2050 and 2070-2095 periods from an ensemble of regional climate models. The predicted changes in snow cover will be moderate for 2021-2050 and become drastic in the second half of the century. Towards the end of the century the snow cover changes will roughly be equivalent to an elevation shift of 800 m. Seasonal snow water equivalents will decrease by one to two thirds and snow seasons will be shortened by five to nine weeks in 2095. Small, higher elevation catchments will show more winter runoff, earlier spring melt peaks and reduced summer runoff. Where glacierized areas exist, the transitional increase in glacier melt will initially offset losses from snow melt. Larger catchments, which reach lower elevations will show much smaller changes since they are already dominated by summer precipitation. © 2013 Elsevier Ltd. All rights reserved.

Prediction of climate change impacts on Alpine discharge regimes under A2 and B2 SRES emission scenarios for two future time periods (2020-2049, 2070-2099)

Abdelkader Mezghani, André Musy, Bettina Schaefli

The present work analyzes the climate change impacts on the runoff regimes of mountainous catchments in the Swiss Alps having current glaciation rates between 0 and 50 %. The hydrological response of 11 catchments to a given climate scenario is simulated through a conceptual, reservoir-based precipitation-runoff transformation model called GSM-SOCONT (Schaefli, 2005). For the glacierized catchments, the glacier surface corresponding to this future scenario is updated through a conceptual glacier surface evolution model. The analyzed climate change scenarios were derived from 19 climate experiments obtained within the EU research project PRUDENCE (Christensen et al. 2002). They are the results of 9 state-to-the-art Regional Climate Models (RCMs) driven by three coupled Atmosphere-Ocean General Circulation Models (AOGCMs), respectively HadCM3/HadAM3H, ECHAM4/OPYC3 and ARPEGE. The two first families of climate change scenarios correspond to changes in seasonal temperatures and precipitations simulated for the period 2070-2099 under the two green house gas emission scenarios A2 and B2 defined by the Intergovernmental Panel on Climate Change (12 experiments are available for A2 and 7 for B2). From the 19 PRUDENCE experiments 19 climate changes scenarios were additionally developed for a transient period (2020-2049) corresponding in first approximation to a global warming scenario of +1°C.

2005

Assessment of climate change impacts on Alpine discharge regimes with climate model uncertainty

Abdelkader Mezghani, André Musy, Bettina Schaefli

The present study analyzes the uncertainty induced by the use of different state-of-the-art climate models on the prediction of climate change impacts on the runoff regimes of 11 mountainous catchments in the Swiss Alps having current glaciation rates between 0 and 50 %. The analyzed climate change scenarios are the result of 19 Regional Climate Model (RCM) runs obtained for the period 2070 – 2099 based on two different green house gas emission scenarios (the A2 and B2 scenarios defined by the Intergovernmental Panel on Climate Change) and on three different coupled Atmosphere-Ocean General Circulation Models (AOGCMs) called HadCM3, ECHAM4/OPYC3 and ARPEGE/OPA. The hydrological response of the studied catchments to the climate scenarios is simulated through a conceptual reservoir-based precipitation-runoff transformation model called GSM-SOCONT. For the glacierized catchments, the glacier surface corresponding to these future scenarios is updated through a conceptual glacier surface evolution model. The obtained results show that all climate change scenarios induce in all catchments an earlier start of the snowmelt period leading to a shift of the hydrological regimes and of the maximum monthly discharges. The mean annual runoff undergoes in most cases a significant decrease. For the glacierized catchments, the simulated regime modifications are mainly due to the increase of the mean temperature and corresponding impacts on the snow accumulation and melting processes. The hydrological regime of the catchments located at lower altitudes is more strongly affected by the changes of the seasonal precipitation. For a given emission scenario, the simulated regime modifications of all catchments are highly variable for the different RCM runs. This variability is induced by the driving AOGCM but also to a large part by the inter-RCM variability. The differences between the different RCM runs is so important that the predicted climate change impacts for the two emission scenarios A2 and B2 are overlapping.

2006

Assessment of climate change impacts on Alpine discharge regimes with climate model uncertainty

Abdelkader Mezghani, André Musy, Bettina Schaefli

2006