Tree-ring reconstruction of climate-induced extreme snow-avalanche events in the Eastern Carpathians (Romania)

Snow avalanches constitute a widespread and dynamic geomorphic process in the Carpathian Mountains, playing a key role in sediment and debris transfer on steep slopes within alpine and subalpine belts. The occurrence, magnitude, and frequency of snow-avalanche events are strongly controlled by climatic factors, particularly snowfall amount, snowpack structure, temperature fluctuations, and extreme weather conditions. In the context of ongoing climate variability, understanding the long-term relationship between climate drivers and avalanche activity is essential for improving hazard assessments in high-mountain regions.

In remote areas of the Carpathians, snow-avalanche hazard assessment is severely limited by the scarcity of systematic observations and the absence of long-term archival records of past avalanche events. This data gap is especially pronounced in the Eastern Carpathians, where documentary evidence of extreme snow avalanches is largely missing. At the same time, increasing human presence and recreational activities in high-mountain environments over recent decades have amplified exposure to avalanche hazards, highlighting the urgent need for reliable, long-term reconstructions of avalanche activity and climate-induced extremes.

This study aims to enhance the understanding of climate-driven snow-avalanche dynamics in the Eastern Carpathians through dendrochronological methods. Multiple avalanche paths located in different mountain ranges were investigated, targeting both coniferous and broadleaved tree species affected by past snow-avalanche activity. Trees disturbed by avalanches were sampled along selected paths, and growth anomalies caused by the mechanical impact and mass movement of snow were identified and precisely dated within annual growth rings. These disturbances include impact scars, tangential rows of traumatic resin ducts, compression wood, and growth-suppression sequences, which serve as reliable proxies for past snow-avalanche events.

By synchronizing avalanche signals recorded in tree-ring series and relating them to regional climatic patterns, this study reconstructs the spatial extent, frequency, and return periods of snow-avalanche events, with particular emphasis on extreme events likely associated with anomalous climatic conditions (e.g., winters with exceptional snowfall, or rapid temperature increases). The results provide insight into temporal variations in avalanche activity and allow the identification of climatically controlled periods of enhanced snow-avalanche occurrence. The dendrochronological reconstruction of climate-induced snow-avalanche activity offers a valuable long-term perspective on avalanche regimes in the Eastern Carpathians. These findings contribute to improved snow-avalanche hazard assessment and zonation and provide a robust framework for evaluating the potential impacts of future climate variability and change on avalanche dynamics at both local and regional scales.