Variability of transparent organic particles in Arctic floodplain lakes

The predominant technique for tracking wildfires uses repeat satellite observations to look for and measure the size of burn scars, the charred remains of once-lush terrain. Because it relies on moderateresolution imagery, this approach has a tendency to miss the smaller fires that, though less widely devastating, can still account for a sizeable portion of the total burned area. Small fires can also have an important effect on the global carbon budget and on air quality. Using a new technique to calculate the global occurrence of small fires, Randerson et al. found that previous measurements had underestimated the total annual burned area by roughly 35%, a difference of about 119 million hectares of land per year. Using a biogeochemical emissions model, the authors suggest that small fires also account for about 35% more global carbon emissions over previous estimates, the equivalent of 0.6 petagram of carbon per year. Though some regions saw only a slight increase in estimated burned area compared with the traditional approach, the authors calculated a 75% spike in burned area for the continental United States after incorporating small fires— an increase in line with other independent estimates. Even larger increases were calculated for regions with tropical forests, including Southeast Asia and Central America. The authors used satellite thermal imaging, which has a much higher spatial resolution than the visible detectors typically used, to calculate the number of active fires both within and outside of observed burn scars. They then tracked surface reflectance changes for these two sets of fires, using the information to estimate the area burned by fires in the different zones. (Journal of Geophysical ResearchBiogeosciences, doi:10.1029/ 2012JG002128, 2012) —CS