| Summary: | The Altai Mountains and also other mountainous areas of Central Asia experienced intermittent cold periods during the 20th-century warming of the Northern Hemisphere. Since the recent cold period in the 1980s, subsequent warm years in the Altai Mountains have accelerated the regional hydrological cycle. Previous studies found changes in snow cover duration, an acceleration of glacier recession, and permafrost degradation related to increasing soil temperatures. An improved knowledge of the long-term climatic variation and its drivers, and their hydrological impacts in the semi-arid mountainous Altai-Dzungarian region is required to better understand and predict impacts on regional agriculture and water availability. Climate observations from this rather inaccessible region are limited; thus, alternative datasets are used in this study. Based on tree-ring proxy data, firstly long-term climate variations were reconstructed back to the Little Ice Age followed by a statistical examination of teleconnections with large-scale atmospheric circulation patterns in order to reveal the driving forces of the regional climate. Secondly, weather station observations and interpolated APHRODITE precipitation and temperature data were used to analyze runoff changes in the Bulgan catchment in response to climate change from 1985 to 2012. Finally, GCM (CanESM2 and HadGEM2-AO) and statistically and dynamically downscaled RCM (SD_CanESM2 and RegCM4) simulations were evaluated and used in estimating future climate and hydrological change from 2030 to 2050 under the RCP4.5 and RCP8.5 scenarios. The hydrological impact of climate change on the predominantly snow-fed Bulgan catchment was assessed by conceptualizing the seasonal melt of glaciers and permafrost in the HBV-Light model. The analysis of tree-rings allowed for the reconstruction of long-term temperature (611 years) and precipitation time series (444 years) in the Altai-Dzungarian region. The results suggest that a cool and wet Little Ice Age was followed by warming in the ...
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