Identifying Hot Moments and Hot Spots of Methane Flux for Accurate Reporting of Greenhouse Gas Budget in Coastal Wetlands

Wetlands can sequester large amounts of carbon from the atmosphere into their soils, however, they also contribute about a third of all the methane emissions to the atmosphere and the processes leading to these high methane emissions remain uncertain and understudied. Part of the uncertainty regarding current and future emissions of methane from wetlands is related to the existence of hot spots and hot moments of methane flux, which have not been clearly identified and understood. In this study, we characterize hot spots of methane flux in a coastal wetland in North Carolina using footprint-weighted flux maps, a new technique develop to map the emission of greenhouse gases around eddy-covariance towers. We studied the Alligator River National Wildlife Reserve in North Carolina where methane and carbon dioxide fluxes are available for several continuous years. In addition, we will report on a new eddy-covariance system that will be installed at the Pocosin Lakes National Wildlife Refuge to continuously monitor MMRV metrics of CO₂ and CH₄ flux at half-hourly intervals. The site will be located on a recently restored subdivision within the wetlands, where the methane fluxes are expected to be higher due to higher water tables. Targeted biogeochemical analyses will be done to better understand the conditions under which the hot spots of methane flux occur. Ultimately, the goal of the project is to better evaluate greenhouse gas emissions from coastal wetlands in North Carolina with high potential for carbon sequestration. In particular, we are interested in detecting hot spots and hot moments of methane flux at the scale of the eddy covariance observation sensor. Studying the biogeochemical properties of these hot spots will allow us to create targeted mitigation strategies to reduce the amount of methane from these ecosystems, thus making these ecosystems more suitable for carbon sequestration practices.