Mechanistic modelling of permafrost: stakes and challenges

Abstract:

Permafrost, i.e. soil that is year-round frozen in depth, covers about a quarter of Northern hemisphere land and occurs mainly at high latitudes. It strongly impacts natural processes and and human activities in these regions, where climate change is especially intense. This Arctic change triggers fast thawing of permafrost, with major consequences for environment and society, at local scale (e.g.: terrain destabilization) as well as at global scale (e.g.: climatic feedback). Anticipating at best the evolution of permafrost under climate warming is thus a critical stake of the 21st century.

Meanwhile, permafrost modelling is extremely challenging. The numerical simulation of thermo-hydrological dynamics in these four-phase porous media is notoriously difficult, involving highly non-linear and coupled processes. The complex physics of transfers in permafrost is characterized by the occurrence of steep fronts and fast transitions related for instance to the phase changes of pore water. This leads to the need of fine spatio-temporal discretizations, and hence to large computation times, especially when dealing with engineering scale problems. The use of High Performance Computing is thus mandatory in this type of application.

This seminar will present the works undertaken at GET since 2010 for developing a permafrost simulator that allow the efficient use of latest generation supercomputers. The applications dealt with in the framework of the ANR-funded HiPerBorea project (2020-2025, hiperborea.omp.eu, 21 millions CPU hours on GENCI supercomputers) will be detailed, and finally the perspectives of developments to be pursued in the framework of the ANR-funded PERMACHANGE project (2026-2029, permachange.sedoo.fr) will be discussed.

Short bio:

Dr. Laurent Orgogozo is a geologist-engineer from the Nancy school of geology, and holds a PhD in civil engineering of the National Polytechnic Institute of Lorraine. He has been hired in 2010 as Associate Professor in Hydrogeology and Hydrology at Toulouse University, doing his research at Geosciences Environment Toulouse laboratory. He is also adjunct-professor at Dalhousie University. His research focuses on permafrost modelling with High Performance Computing, with applications to environmental monitoring sites and human settlements in Boreal Eurasia and in the European Arctics. To date he has successfully attracted 1.2 million euros research funds from the ANR, being the scientific coordinator of the HiPerBorea project and the PERMACHANGE project. He was also granted more than 24 millions CPU hours so far on regional to national French supercomputers. Dr. L. Orgogozo is Associate Editor at Journal of Mountain Sciences and at Scientific Reports.