Synergistic effects of warming and heavy snowfall accumulation on the increased risk of large-scale snow avalanches in the western Tianshan Mountains

Climate change has increased temperatures and altered snowpack properties, which in turn affect avalanche activity. The extent to which climate change affects avalanche activity and how avalanche activity responds to climate change remains poorly understood, which hinders avalanche risk assessments under future climate change. In this study, we applied tree-ring evidence from trees affected by avalanches to reproduce historical avalanche events and then combined the observed meteorological and snowpack data to reveal the response mechanism of avalanche activity to climate change in the Tianshan Mountains. The study found that snow seasons with large-scale avalanche events have increased since 1943, which is contrary to the assumption that less snow under a warming climate reduces the risk of avalanches. Snow seasons in which large-scale avalanches occur are characterised by high snow depth in November (>44.4 cm) and April (>60.9 cm), together with low December temperatures (<−1.9 °C) under heavy snowfall (≥34.4 cm). Under climate change, the study area experienced a marked increase in snow season temperatures along with rising trends in snow depth and heavy snowfall, leading to elevated avalanche risk in the middle altitudes of the western Tianshan Mountains, where human activities are intensive. This study provides a clear understanding of avalanche risk changes in the region under climate change and helps people propose climate-change adaptation strategies for avalanche risk.