B027-03
Changes in trace gas radiative forcing of Stordalen Mire from 1970-2014
Tuesday, 8 December 2020: 17:38
Virtual
Ruth K Varner, University of New Hampshire Main Campus, Durham, NH, United States, Patrick M Crill, Stockholm University, Stockholm, Sweden, Steve E Frolking, University of New Hampshire, Institute for the Study of Earth, Oceans, and Space, Durham, NH, United States, Michael W Palace, University of New Hampshire, Dept. of Earth Sciences and Earth Systems Research Center, Durham, NH, United States, Carmody K McCalley, Rochester Institute of Technology, Rochester, NY, United States, Jeff Chanton, Florida State University, Tallahassee, FL, United States, Beth Holmes, Florida State University, Dept. of Earth, Ocean, & Atmospheric Science, Tallahassee, FL, United States, Scott R Saleska, University of Arizona, Department of Ecology & Evolutionary Biology, Tucson, AZ, United States and Virginia Isabel Rich, University of Arizona, Tucson, AZ, United States
Abstract:
Permafrost thaw increases the active layer, changes soil moisture and influences vegetation species composition These changes along with belowground microbial and geochemical changes, impact production, consumption and net emission rates of radiatively important trace gases. The rate at which carbon dioxide (CO2) and methane (CH4) are taken up and released from these dynamic, climate-sensitive ecosystems ultimately determines their radiative forcing. Permafrost peatland landscapes are a mosaic of frozen hummocks (palsas), semi-thawed sphagnum dominated areas (bogs), permafrost-free sedge dominated areas (fens) and open water ponds formed through the collapse of permafrost.
Here we present an updated time-series of radiative forcing at three temporal snapshots over a 45 year period; 1970, 2000 and 2014 for the Stordalen Mire, a permafrost peatland located in the discontinuous permafrost zone of Northern Sweden. Exchange rates of carbon dioxide and methane from the terrestrial landscape were taken from eddy covariance, automated and manual chamber measurements. Emission from open water surfaces were measured using floating chambers and ebullition (bubble) traps. Aerial photos combined with plot based measurements and unmanned aerial systems and remote sensing were used to determine dominant landcover types and areal extent for each time period. Our results indicate that the mire is continuing to transition from dry, permafrost to wetter, more sedge dominated sites. The Stordalen Mire Global Warming Potential (GWP) as calculated using IPCC 2013 guidelines has gone from negative to positive over the 45 year period. This new mire-wide estimate of climate forcing is driven by increases in the 100-yr GWP of methane from 25 to 28, vegetation community composition transition due to permafrost thaw and improved estimates of annual GHG exchange for the major land cover types. These results indicate that discontinuous permafrost ecosystems, while still remaining a net sink of C, can become a positive feedback to climate change on decadal timescales.
