B038-0008
Methane flux attribution analysis applied on eddy covariance measurements at heterogeneous wetland sites

Wednesday, 9 December 2020
Poster
Mathias Goeckede, Max Planck Institute for Biogeochemistry, Jena, Germany, Etienne Fluet-chouinard, Stanford University, Earth System Science, Stanford, CA, United States, Ankur R Desai, University of Wisconsin Madison, Madison, WI, United States, Benjamin Runkle, University of Arkansas, Fayetteville, AR, United States, Oliver Sonnentag, Université de Montréal, Département de Géographie, Montréal, QC, Canada, Eric Ward, U.S. Geological Survey, Wetland and Aquatic Research Center, Lafayette, LA, United States and Lisamarie Windham-Myers, U.S. Geological Survey, Water Mission Area, Menlo Park, CA, United States
Abstract:
Flux tower measurements of CH4 flux from wetlands may be highly dependent on variation in wind direction, yet the importance of directionality as a systematic problem across towers in a network is not well characterized. In this study, we develop a metric for screening the importance of wind directionality for interpretation of CH4 fluxes across a global network of 60+ towers. We take a clustering approach to identify whether flux and wind direction jointly indicate the presence of distinct patches surrounding the tower. Our directionality metric also allows flagging measurements and/or sites where wind directionality is confounding the effects of drivers of methane production and transport.

We discuss the significance of considering directionality on flux data filtering, gap-filling and upscaling. Examples of the application of this approach include analysis from eddy-covariance case studies from distinctive sites, such as heterogenous boreal peatlands (e.g. CA-SCC) where landscape CH4 emission hot spots are captured only under certain wind directions. “Homogeneous” agricultural landscapes, such as precision-leveled rice fields at US-HRA, also can show wind directionality effects, whereby spatial gradients in soil conditions (e.g., texture and organic carbon content) induce changes in CH4 production in different wind-direction sectors. Case studies will demonstrate the role of wind-direction assessment for temperature response functions necessary for upscaling, projecting responses and identifying sub-footprint heterogeneity for flux chamber deployments. The clustering approach to temperature response function allows identification of confounding effects of soil moisture, salinity inflow at marshes, and potential effects of changing wind rose distributions from year to year.

We thank the FLUXNET-CH4 contributors and the Powell Center Wetland Methane working group for the data provided in these analyses.

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