Net radiative forcing potential of landscapes in Beringia from carbon dioxide (CO2) and methane (CH4) exchange

Background/Question/Methods While many studies focus on the carbon sink/source function of ecosystems, recent studies have highlighted the increased radiative forcing effect of methane (CH4) over carbon dioxide (CO2). As a greenhouse gas, CH4 has 25 times the global warming potential of CO2. Therefore, it is possible for a landscape to be a net carbon sink, while still having a net positive radiative forcing on climate. Accounting for both CO2 and CH4, this study calculates the radiative forcing potential of landscapes within arctic Beringia by performing a spatial extrapolation of ecosystem properties across the current distribution of land cover types. During the peak of the 2005-2007 growing season, 10 landscapes across Beringia were sampled using a rapid ecosystem assessment technique. Sampling results were used to create land cover classifications of each site using Quickbird satellite imagery. Results/Conclusions Russian sites in Chukotka and Wrangel Island had very low overall rates of gas exchange (-1.66 – 2.61 g CO2-C m-2 day-1, -0.002 – 0.05 g CH4-C m-2 day-1) compared to sites in the Seward Peninsula and North Slope of Alaska (-12.56 – 7.61 g CO2-C m-2 day-1, -0.06 – 0.28 g CH4-C m-2 day-1). The mean methane emission for all dry sites was -0.01 ± 0.008 g CH4-C m-2 day-1. The across all sites, the natural log of CH4 emission increased with increasing soil moisture (r2 = 0.479, p < 0.001). Although wetter sites had greater methane emission, they also had higher productivity in general. Net radiative forcing potential did not show any trend across land cover types. Differences in local environmental factors between sites likely play a strong role in determining whether sites were a net positive or negative radiative forcing on climate.