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Improving our process understanding of methane emissions from a mid-latitude reservoir by combining eddy covariance monitoring with spatial surveys
Citation:
Waldo, S., J. Beaulieu, AND Johnt Walker. Improving our process understanding of methane emissions from a mid-latitude reservoir by combining eddy covariance monitoring with spatial surveys. AGU Fall Meeting, New Orleans, LA, December 11 - 15, 2017.
Impact/Purpose:
The purpose of this presentation is to share scientific information and methods with peers in the community.
Description:
Reservoirs are a globally important source of methane (CH4) to the atmosphere, but measuring CH4 emission rates from reservoirs is difficult due to the spatial and temporal variability of the various emission pathways, including ebullition and diffusion. We used the eddy covariance method to measure fluxes of CH4 over a mid-sized (2.4 km2), eutrophic reservoir in southeast Ohio, US from winter thru fall of 2017. In addition to the eddy covariance system, we deployed inverted funnels to monitor ebullitive fluxes, and a thermistor chain to relate underwater convective mixing to the air-water gas exchange. Methane emissions increased from winter to summer, with average fluxes of 10.0 mg CH4 m-2 d-1 and 190 mg CH4 m-2 d-1 in February and June, respectively. While no clear diurnal pattern in emissions emerged from the eddy covariance results, “pulses” in CH4 emissions were observed that coincided with synoptic weather events and destratification of the water column. Details on the physical drivers of these pulse events and how they enhance CH4 emissions via the diffusive or ebullitive pathways will be discussed.