Center for Permafrost (CENPERM) > Cenperm background
Soil ecosystems with underlying permafrost cover ~25% of the land area in the Northern Hemisphere and store almost half of the global soil carbon (C). Future climate changes are predicted to have the most pronounced effect in Northern latitudes and these Arctic ecosystems are therefore subject to dramatic changes following thawing of permafrost, glacial retreat, and coastal erosion. The most dramatic effect of permafrost thawing is the accelerated decomposition and potential mobilization of organic matter stored in the permafrost, impacting global climate through the mobilization of carbon and nitrogen (N) accompanied by release of greenhouses gases (GHG) as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The net effects of these changes are controlled by coupled feedback mechanisms which impact will differ with respect to climate, amount of C and N stored in the soil, ice content, temperature and active layer dynamics. As awareness and concern of recent rapid climatic changes in the Arctic grows, so does the need for a long-term perspective on these changes and improved knowledge on the nature of the coupled biological and climatic feedback mechanisms following accelerated permafrost thawing. Permafrost is currently not well represented in global models and the lack of representation of permafrost-influenced climate feedback is a recognized source of uncertainty.
Arctic ecosystem feedback mechanisms and processes interact on micro, local and regional scales. As recently highlighted, this is further complicated by several potential feedback mechanisms likely to occur in permafrost-affected ecosystems, involving the interaction of microorganisms, vegetation and soil:
- heat production linked to microbial activity and resulting in accelerated warming
- microbial priming effects that leads to mobilization of "old", recalcitrant organic matter through microorganisms activated by labile C input from "young" biomass (for example from increased plant growth as a consequence of climate warming) and subsequent net carbon loss
- positive feedbacks linked to the nitrogen (N) cycle, including increased mineralization rates, N release from thawing permafrost, and increased plant growth as a consequence of enhanced N availability for plants.
Neither of the above-mentioned processes has yet been integrated in a landscape approach, nor have they been quantified simultaneously by assessing the complex interactions between permafrost dynamics, microbial activity and plant growth. Processes are so poorly understood that incorporation into global climate models has not been attempted for long term predictions. This requires large-scale field manipulation experiments coupled to studies of activity of microorganisms and responses of plants and the integration of C cycling with other elements, particularly N. Furthermore, new insight in permafrost processes needs to be scaled up to assess the regional importance of future changes. Processes in the uppermost active soil layers have more or less been successfully scaled up based on different vegetation and soil indices. New tools are needed as permafrost characteristics cannot be scaled similarly. In conclusion, it remains one of the most formidable challenges facing leading scientists already working in Greenland to put all efforts into one ambition: CENPERM.