Regional CH4 column gradients over Tanana Flats wetlands in interior Alaska

Understanding the regional dynamics of atmospheric methane (CH4) in northern wetlands is critical for modeling global greenhouse gas fluxes and feedbacks. Regional scale CH4 flux estimates from ecosystem models need to be validated by regional-scale observations. While aircraft observations have traditionally been used for regional model validation, aircraft campaigns are expensive and sparse in spatial coverage. New methods for estimating fluxes using column-averaged dry air mole fractions of CH4 (XCH4) retrieved from portable, solar-viewing Fourier transform infrared spectrometers (FTS) offer cost effective approaches for model and satellite validation on a regional scale. In this work, we report gradients in XCH4 observed among multiple locations around the Tanana Flats wetlands in interior Alaska. Methane column gradients were observed between Fairbanks and Nenana with two Bruker EM27/SUN FTS in August through October of 2016 and between Nenana, Fairbanks, and Salcha with three EM27/SUN FTS in June of 2018. These observed CH4 column gradients will be compared with estimates of XCH4 enhancements generated from convolving STILT footprints and ecosystem flux estimates from the Terrestrial Carbon Flux (TCF) model. This work is the first use of column greenhouse gas gradient measurements in the Arctic to validate regional-scale ecosystem flux models and can provide the basis for future analysis of XCH4 observed by satellite-based instruments such as TROPOMI.