Grant: Alliance Grants

Temperatures are rising at disproportionally high rates in Arctic regions. This accelerated warming is rapidly altering the water, carbon and energy cycles in these regions. Permafrost soils that represent 25% of northern hemisphere lands are estimated to store up to 1,600 billion tons of soil carbon (carbon dioxide, CO2 and methane, CH4), representing roughly twice the amount of carbon currently stored in the atmosphere. In addition, growing evidence suggests that Arctic soils may also be relevant sources of nitrous oxide (N2O). The potential to emit enormous quantities of GHG (CO2, CH4, N2O) from the Arctic could play a central role in the climate system and further accelerating warming in Arctic regions, negatively impacting transport, food security and well-being of Inuit community. Warming soils have promoted permafrost degradation and active layer deepening, enhancing the mobilization and potential transfer of soil GHG to the atmosphere. However, large uncertainties are related to the GHG budget in Arctic regions. The amount of CO2 released during winter periods varies spatially depending on vegetation type and non-frozen soil moisture, while deeper and more insulating snow cover has been linked to warmer soil temperatures producing larger CO2 fluxes. These complex snow/vegetation /soil temperature interactions could also affect CH4 and N2O emissions mostly in shoulder seasons, where soil temperatures remain close to zero for a prolonged time. Considering the importance of Arctic winter GHG emissions, there is an urgent need to develop capabilities to measure continuously in-situ winter-long GHG emissions along with the key driving variables (soil moisture/temperature, soil type and characteristics, vegetation, and snow characteristic) and use these to develop mechanistic process-based models. The goal of this project is to improve our predictive understanding of winter GHG emissions by 1) monitoring winter-long GHG fluxes over four Canadian Arctic experimental sites, and 2) improve CLASSIC's capacity to simulate these fluxes. 1. Characterize spatial and temporal winter season GHG fluxes in four Canadian Arctic environments: We will monitor Arctic winter GHG fluxes (CO2, CH4,and N2O) using the snow gradient method at four Arctic locations and deployed winter soil respiration monitoring systems (Forced Diffusion technology sensors [eosFD, Eosense Inc., Dartmouth, NS]37, with spatially distributed measurements of soil moisture and temperature. Comprehensive snow, vegetation and soil characteristics measurements will be taken to improve understanding of the factors affecting GHG fluxes in Arctic winter environments. 2. Improve snow and winter GHG fluxes simulation in CLASSIC: We will use measurements from Objective 1 to improve simulations of GHG fluxes in CLASSIC. CLASSIC snowpack and soil temperature simulations will be improved by developing a 2-layer tundra snowpack module and improving the characterization of winter soil thermal and moisture conditions.