Vegetation Disturbance Triggers Greenhouse-Gas Emitting Feedback Loop in Permafrost

by Lindsay McCord

Vegetation changes have the ability to rapidly destabilize permafrost soil, illustrating vulnerability of these ecosystems to disruptions. Study sites that removed shrub vegetation experienced both increased thaw depth of permafrost as well as soil subsidence, lowering the permafrost table by 31 cm in comparison to control sites. This created localized wetlands of water-saturated depressions, which become hotspots for additional thawing as well as increased methane emissions. Continue reading

Anthropogenic effects on greenhouse gas (CH4 and N2O) emissions in the Guadalete River Estuary (SW Spain)

by Rebecca Herrera

Burgos et al. (2014) discuss seasonal variations of the greenhouse gases methane (CH4) and nitrous oxide (N2O) in the Guadalete River Estuary ending in the Cadiz Bay of southwestern Spain. They found that greenhouse gas concentrations were higher in the more inland parts of the estuary compared to the mouth of the river. Concentrations of methane and nitrous oxide varied depending largely upon the seasonal precipitation regime. It was also observed that the Guadalete Estuary acted as a source, rather than a sink, of greenhouse gases throughout the entire year, as observed by measuring the fluxes of CH4 and N2O from the Estuary. Continue reading

Modeling CO2 and CH4 Fluxes in the Arctic using Satellite data

by Rebecca Herrera

The peatlands and tundras of the Arctic perform vital ecosystem services to the earth through their ability to sequester carbon (CO2) and methane (CH4) and function as a carbon sink. The ability of the permafrost in the peatlands and tundra ecosystems of the Arctic to continue to function as a natural reservoir for carbon and methane may be disrupted by rising global temperatures that increase the rate of soil decomposition. Watts et al. (2014) integrate a terrestrial carbon flux (TCF) model to include a newly developed CH4 emissions algorithm. The new TCF model simultaneously assesses CO2 and CH4 fluctuations and the corresponding net ecosystem carbon balance (NECB), which is contingent upon gross primary productivity (GPP) subtracted from ecosystem respiration. The integrated TCF model uses data gathered through satellite remote sensors to assess fluxes in CO2 and CH4. Continue reading

Just How Much Methane is Released in California?

by Emil Morhardt

On the occasional foggy day in Claremont, one can be nearly bowled over by the smell of dairy farms—not a smell that mixes well with the usual orange blossom/eucalyptus fragrance permeating the campus of the Claremont Colleges. The smell is wafting over from the eastern South Coast Air Basin (SoCAB), which, along with California’s Central Valley is the focus of a new top-down estimate of methane emissions by Yuyan Cui  and colleagues at NOAA and the University of Colorado in Boulder, Harvard University, and the University of Michigan. Top-down estimates are based on measurements of methane made from above—in this case by aircraft—rather than based on ground-based considerations, such as counting the number of dairy cows and multiplying by how much methane each is thought to produce. One object of the study was to provide data for use by the State of California in attempting to assure that statewide greenhouse gas emissions not exceed 1990 levels by 2020. The study used some fancy inverse modeling to trace the concentrations measured aloft to their sources, and to calculate that total emission levels. The results corroborated those of several other recent studies, showing that twice as much methane is being emitted than was estimated by the USEPA in 2005, something on the order of 426 Gg (Gigagrams, millions of kilograms) per year. In the eastern SoCAB it, sure enough, is coming from the dairy cattle. In the western SoCAB, where there aren’t any, it comes from landfills, wells, and other un-described point sources. Continue reading