||The melting of polar ice is an indication of a warming trend in the Arctic and Antarctic regions. In the Arctic, continental soils cover 8.6% of the Earth land area but may as much as 50% of the total global soil organic carbon. Most of this Carbon is permanently stored because soils are frozen forming the so-called permafrost. The current and predicted warming trend in northern latitudes may lead to deterioration of permafrost Carbon, eliciting its decomposition and increasing the levels of greenhouses gases in the atmosphere, potentially creating a positive feedback on the warming trend of the whole climate system. In Arctic Alaska, current and predicted atmospheric air warming will likely lead to increases in winter precipitation, resulting in a deeper snow cover. A thicker snow layer over the soil will act as a thermal insulator, further enhancing the degradation of permafrost and stored soil C, decreasing the Arctic C pool. However, warmer soils will also release soil nutrients which may elicit increases in the productivity of vegetation, enhancing Carbon inputs to soils and creating a negative feedback on the warming trend of the climate system. The balance of these two feedbacks will determine to what extent Arctic ecosystems will become a major source of greenhouse gases in the atmosphere.
To evaluate the positive and negative feedbacks we will use artificial winter snow accumulation using snow fences at the LTER research stations at Toolik Lake, Alaska. These treatments emulate the increased snow winter accumulation and the winter thermal insulation of the soils. We used an experiment set in 1996 and a new one established in 2006 by one of the co-Pis of the project. In these long- and short-term experiments we will investigate the strength of the positive and negative feedbacks on greenhouse emissions from Arctic soils. Using weapon-derived and natural radioisotope tracers combined with biogeochemical techniques, our first year results suggest that increased emissions of Carbon dioxide from permafrost soils maybe compensated for by increased C inputs from growing vegetation. However, increased emissions of methane (a more potent greenhouse gas than carbon dioxide) at the warmer sites suggest tundra will become a source of greenhouse gas equivalents in the future.