Permafrost covers over 20% of land masses in the Northern hemisphere. Its thawing due to global warming could release tens of Pg of carbon in the form of CO₂ and CH₄ to the atmosphere, representing a major positive feedback to warming. Permafrost thawing also impacts Northern communities and on the development of the Arctic.
The snow cover is a major factor in the energy budget of permafrost, because it acts as an insulating layer that limits winter ground cooling. The thermal conductivity of the snow is highly dependent on climate and vegetation, so that there exists strong feedbacks between vegetation, snow, climate and permafrost. The purpose of this project is to perform continuous measurements of the thermal conductivity of the snow and the surface soil layer at different Nordic sites to provide data to quantify these feedbacks using snow and land surface models.

Campaign 2013

The main goal of the program is to understand the relationships between climate, vegetation, snow physical properties, and the energy budget of permafrost. Ultimately, we hope to contribute to the quantification of feedbacks between these four topics and be able to model all these interactions to improve our prediction of the rate of permafrost thawing. To that end, we propose to deploy novel instruments to monitor snow physical properties, and in particular its thermal conductivity, in several subarctic and arctic sites whose vegetation range from forest tundra (i.e. open forest usually comprised of short spruce) to herb tundra, and whose permafrost range from recently disappeared to thick continuous. These data will be used by collaborating modeling groups who will improve snow physics models and land surface models based on our campaign work. Snow and permafrost will then be modeled at our study sites for testing before being used in Arctic-wide simulations.
During the 2012-2013 season, which is not completed as of writing, we have or will have:
- Done exploratory work to select sites suitable for instrument deployment. This was done in March 2012 and two sites were selected near Umiujaq, northern Quebec (56°N). Umiujaq is an ideal site, as it is situated in the transition region between continuous permafrost along the coast of Hudson Bay, and disappearing permafrost to the south. One selected site is in forest tundra, featuring 5 m-tall spruce and 2 m-tall shrubs. The permafrost there has disappeared. The other site is in low shrub tundra, with about 20-cm shrubs, with shallow permafrost.
- Deployed instruments at both sites. This includes instruments to measure the temperature and humidity profile of permafrost, the thermal conductivity an thermal diffusivity of the top soil layer using a Hukseflux TP01 probe, the temperature and thermal conductivity profile of the snow using Hukseflux TP02 probes, and meteorological variables : radiation (upwelling and downwelling shortwave and longwave) using a heated and ventilated CNR4 from Kipp and Zonen, wind speed, and air temperature and relative humidity. This will be done in September 2012. All instruments have been purchased and received. Vegetation at our sites will also be studied in detail with our collaborators.
- Performed snow pit measurements at the beginning of the season, in early January 2013, in order to validate and complement data from the measurement stations with additional data such as density and specific surface area profiles, and also to further explore spatial variability of snow properties in order to improve the representativity of our sites. It is also essential to perform measurements at the beginning of the season (January). The data obtained, in conjunction with those planned in March 2013, will be useful in understanding the time-evolution of snow physical properties. Data will also be downloaded at that time.
In continuation of this work, during the 2013-2014 season, we plan to:
- Perform additional snow pit measurements in March 2013, similarly to what was done in March 2012. As mentioned above, this will complement our January 2013 data, and document the understanding of the transformations of the snowpack as a function of vegetation cover.
- Purchase instruments to build another snow and permafrost station and deploy it at Bylot Island. The centre d’Etudes Nordiques has a research station on this island, located at 73°N just North of Baffin Island. The environment is herb tundra and very thick continuous permafrost. For our objectives, this site will be representative of the high Arctic. Initially, we had planned to move one Umiujaq station to Bylot Island, but obtaining just one year of data at Umiujaq is not sufficient, because of interannual variability and because of the risk of instrument failure, in particular because of damage by wildlife. Even though our Canadian collaborators are very experienced and use many trick to minimize risks, it is obvious that problems can still happen.
In parallel to these field operations, our collaborators at LGGE and CNRM-GAME (Toulouse and Grenoble sites) will start using our data for initial tests and model improvements.