Tree-ring reconstruction of snow avalanche activity: Does avalanche path selection matter?

Area of Science:

• Geosciences
• Climatology
• Ecology

Background:

• Anthropogenic global warming necessitates long-term mass movement chronologies to detect temperature-related trends.
• Dendrogeomorphic reconstructions often underestimate historical avalanche activity, with estimates typically around 50% lower than documented.
• Existing research attributes underestimation to event magnitude, overlooking other factors.

Purpose of the Study:

• To investigate the impact of avalanche path morphometry and forest cover on the length and reliability of tree-ring reconstructions.
• To compare the dendrogeomorphic reconstruction potential of differently structured avalanche paths in the French Alps.

Main Methods:

• Selection of four adjacent avalanche paths with varying structures in the Queyras massif.
• Comparison of tree-ring records with historical archives to assess reconstruction accuracy.
• Analysis of avalanche path characteristics, including altitude, vegetation, and slope, in relation to reconstruction data.

Main Results:

• Tree-ring reconstructions on active, high-altitude, shrub-covered paths were limited to one century, with high-magnitude events every >25 years.
• Forested couloirs with lower slopes and forest cover up to release areas yielded avalanche reconstructions 2.5 times more frequent.
• Reconstructions from forested sites spanned longer periods and showed higher convergence with historical archives, indicating greater reliability.

Conclusions:

• Avalanche path characteristics, particularly forest cover, significantly influence the quality of dendrogeomorphic reconstructions.
• Forested avalanche paths are crucial for obtaining exhaustive and reliable long-term reconstructions of snow avalanche activity.
• Prioritizing forested sites enhances the accuracy and temporal scope of dendrogeomorphic analyses for climate change studies.