3e série de séminaires CLIMACT - Episode #8

The rise in global mean temperatures induced by climate change causes accelerated permafrost degradation. In high mountain rock slopes, rock falls in permafrost areas are triggered by decreasing restraining forces such as friction loss in joints or fatigue of rock bridges. Although our knowledge of the thermal influence on permafrost degradation has improved over the last decades, its mechanical effect on rock slope destabilization remains rather poorly understood.

In this presentation, Johan Gaume and his team modeled the Mont fort geological structure (Verbier, CH) using the 3D Distinct Elements Numerical Method (3DEC software) to simulate and analyze rock failure processes. Their developed thermo-mechanical joint model simulates the main permafrost rock destabilization processes, i.e. joint strength temperature dependency. The results show that temperature changes affect the rock stability deeper than the active layer.

The study advances the understanding of thermo-mechanical failure processes in permafrost rock slopes, with several potential applications in structural engineering and natural hazards.

In the context of current climate change trajectory, carbon dioxide removal technologies are receiving increasing interest. Among existing approaches, enhanced weathering (EW) represents a promising methodology relying on soil amendment with powdered silicate rocks to accelerate natural chemical weathering and associated atmospheric CO2 uptake. However, EW is still in early stages of evaluation with efficiency estimates often based on simplified representations of soil biogeochemical and hydrological transport processes, either from small-scale experiments or global-scale models.

Here, the project team developed a synthetic model linking expected CO2 capture with natural and technology-related CO2 emissions to assess the relevance of EW in Swiss croplands. Combining available techno-economic and specific carbon sequestration data with usually unaccounted geochemical processes, they show that the timescales to achieve net CO2 sequestration are highly variable and generally not satisfying current mitigation targets. These results provide a critical assessment of EW implementation and identify major blind spots underlying its effectiveness.

In this presentation, Antoine Vialle will briefly summarize the goal and developed approached of my Climact-granted research project on carbon sequestration in urban soils within urban requalification projects. In particular, he will highlight how he took advantage of the so called “starting” grant as a seed money at an early stage of his researcher career by commenting the significant deviations from his initial proposal in terms of main scientific and societal outputs, but also critical challenges.

The project team combines modern aircraft-based sensors with deep-learning data analysis and in-situ observations to generate spatially explicit inventories of species in the treeline ecotone within one Alpine valley. When validated, the approach is intended to be extended over broad regions where in-situ measurements are not feasible and satellite imagery does not provide a sufficient level of detail. This information should enhance the forecasting capacity of species distribution models designed to predict the evolution of vegetation as a result of climate warming.

Jan Skaloud presents the methodology to achieve this goal after the envisaged approach had to be redesigned during the project, as the data collected by the world’s finest imaging spectrometer for the study did not meet the localization accuracy required. This highlights the importance of having the ability to implement and control all stages of the processing chain in-house and to present data openly in their raw form.