Thursday, August 4, 2016

Trace Gas Emissions on the Tundra

Greenhouse gas emissions, including the flux of CO2 and CH4 from terrestrial ecosystems, provide an important land-atmosphere feedback to climate. As such, the NGEE Arctic project has several tasks that target a mechanistic understanding of the processes that control the carbon cycle. This applies not only to our field and laboratory studies, but also to our modeling where it is critical to properly represent the timing, rate, and magnitude of CO2 and CH4 flux from plants, soils, and ecosystems.

This week Ori (LBNL) and others are busy measuring trace gas flux at locations across the landscape at our field site near Council, AK. You may remember Ori from her work in Barrow where she has been helping with our measurements since 2014. Using similar techniques as those perfected at Barrow, Ori is working this week to deploy a network of chambers that will allow our team to determine how the flux of CO2 and CH4 varies in tussock tundra and in areas where permafrost thaw and thermokarst formation are underway. Ori has installed PVC bases into the soil at dozens of locations across the field site. She is using a portable gas analysis system from Los Gatos Research to measure flux rates by first placing a clear or opaque chamber on the PVC bases. An air-tight seal ensures that both the increase and decrease of CO2 and CH4 concentration can be measured, from which rates of ecosystem gas exchange can be estimated.

Field-scale measurements of CO2 and CH4 flux will be important for quantifying whether tundra ecosystems are a source or sink for carbon. More importantly these data, and the knowledge derived from them, will guide more mechanistic studies under controlled conditions in the laboratory and validate how those mechanisms are represented in models. The results that Ori and others gain this week will also help us prepare for more intensive measurements next year.