Abstract
Knowledge about changes in ground temperatures under a changing climate are important for many environmental, economic and infrastructure applications and can be estimated by transient numerical simulations. However, a full annual cycle of precipitation data is needed to achieve this, yet is often unavailable in high alpine regions where a lack of infrastructure precludes installation of heated instruments capable of measuring the solid precipitation component. This paper presents a method to reconstruct a full year precipitation dataset at high alpine weather stations, which is then used to model ground temperature and snow depth for 16 alpine sites in Switzerland for the past and three climate scenarios. Differences in the possible temperature trajectories are highlighted with a focus on elevation and regional climatic differences within Switzerland. Snow height and ground temperatures under a changing climate are modelled with the one- dimensional physical model SNOWPACK by applying a delta change signal to the meteorological data set obtained from the CH2011 climate scenarios of Switzerland. All sites showed a decrease of snow cover, a shortening of the snow season and an increase in ground temperature to the end of the century. Sites in the inner alpine regions of Grisons were found to be less sensitive to climate change than sites in the western Alps. The magnitude of reduction of mean snow height depends mainly on location, whereas for the contraction of the snow season elevation is the key factor. It could be shown that the temperature - precipitation combination as expressed in the snow dynamics explain changes in ground temperatures more than the individual changes in either parameter. Alpine meadow and thin snow cover appear to delay warming of the ground.
Highlights
The impact of climate change on the ground thermal regime of high mountain environments remains uncertain in many aspects, due in part to complex processes involving mass and energy exchanges with the winter snow cover
We found that modeling future periods with the climate change signal directly, does not reveal any significant difference, compared to a transition run from 2000 to 2100 which had been performed for one regional climate model at Weissfluhjoch
As all of the stations are located in high alpine regions and have a continuous snow cover between December and end of winter, a melt-out day can be identified using this definition
Summary
The impact of climate change on the ground thermal regime of high mountain environments remains uncertain in many aspects, due in part to complex processes involving mass and energy exchanges with the winter snow cover. Dedicated permafrost studies have been carried out to both establish the current state (Luetschg and Haeberli, 2005) and future evolution of the ground thermal regime in various case-study locations (Noetzli et al, 2007; Ravanel et al, 2017) These have either focused on permafrost areas exclusively, slope stability issues or rockwall dynamics. Snow cover can change mean annual ground temperature by several degrees and the overall effect depends on snow depth, the date of the onset of snow cover in winter, the duration of the snow covered period, snow density and the date of the snow cover melt-out in spring/summer (Haeberli, 1975; Zhang, 2005). To overcome this problem a method to reconstruct a full year precipitation data set at each AWS is presented
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