Conférences du CEN
Jeudi, le 14 novembre 2013
13h00 à 14h30
Pavillon A. Vachon, local 3068, Université Laval
Professor at the Department of Geography & Environmental Studies, Carleton University
Measuring and Simulating Permafrost Thaw
Permafrost underlies much of Earth’s surface and interacts with climate, land-surface phenomena and human systems. This presentation highlights heterogeneity and near-isothermal ground, two simple and well-known phenomena, as important challenges for investigating current and future states of permafrost, and outlines possibilities to meet these challenges. Heterogeneity, which can be introduced by e.g., topography, vegetation or subsurface material, is shown to be important for large parts of the global permafrost areas based on two proxies calculated from a global model of permafrost distribution. The model is based on a 1km DEM and NCEP-NCAR as well as CRU TS 2.0 air temperature data. Near-isothermal ground occurs when heat flow into a volume of ground material is accompanied by only a minute temperature change due to the dominance of latent heat transfer near 0°C. This causes our monitoring systems, which are to a large part based on temperature measurements, to lose much of their sensitivity as an instrument to measure permafrost changes. The importance of this is argued for based on (a) the long duration that soil columns are usually exposed to this effect, (b) the abundance of boreholes with temperatures close to 0°C based on the IPY-TSP data set, and (c) the global abundance and relative importance of ground near 0°C. The results presented indicated that systems and methods of gathering permafrost evidence and monitoring data need to better account for heterogeneity and isothermal ground in order to maintain long-term relevance, and that in large-area models sub-grid heterogeneity needs explicit attention.