Séminaire ISTerre

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Impact of Past and Current Climatic Forcings on High Mountain Hazards

mercredi 29 mai 2024 - 10h00

Benjamin Lehmann  - séminaire post-doc (café 9h45 salle convivialité)
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In high mountain regions, which are home to approximately 10% of the world's population, climate change is causing glacier retreat and permafrost degradation, thereby creating natural hazards for ecosystems and local societies. However, the study and monitoring of gravity-driven hazards related to the cryosphere remain limited. Understanding the mechanisms controlling the geomorphological response to climate changes and the associated hazards is crucial for anticipating the impacts of climate change and preparing a sustainable future for Andean societies. This response includes a long-term perspective, over scales of 1,000 to 10,000 years, concerning glacial fluctuations and associated topographical conditioning, as well as a recent impact of climate change, over scales of 10 to 100 years, manifested by glacier retreat and permafrost degradation. My work focuses on quantifying the geomorphological response of high mountain landscapes to past and current climate changes. The objective is to better understand the dynamics of associated hazards and resources. I approach this issue through a multidisciplinary methodological approach adapted to high mountain geomorphology, combining field measurements, remote sensing, geochronology, and numerical modeling. This approach allows for an integrated understanding in space and time of the geomorphological evolution of high mountain environments, particularly cliffs and slopes, covered and rock glaciers, as well as gravity-driven instabilities. Thus, I reconstruct the activity of rock glaciers and the history of cliff erosion. The objective is (i) to extract (paleo-)climatic data, (ii) to characterize the factors controlling cliff erosion, and (iii) to quantify the evolution of permafrost and water resources in high mountain areas. Finally, I study the hazard of rock-ice avalanches by quantifying their spatial distribution, frequency, and magnitude, in close relation to past climatic oscillations, covering the Holocene to the Late Pleistocene. The primary question is: can geomorphological archives help explain the increase in current instabilities and predict future hazards?

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Equipe organisatrice : Organisation labo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères