Qing Ying (1), Benjamin Poulter (2), Jennifer Watts (3), Kyle Arndt (3), Anna-Maria Virkkala (3), Lori Bruhwiler (4), Youmi Oh (4), Brendan Rogers (3), Susan Natali (3), Hilary Sullivan (3), Luke Schiferl (5), Clayton Elder (6), Olli Peltola (7), Annett Bartsch (8), Amanda Armstrong (2), Ankur Desai (9), Eugénie Euskirchen (10), Mathias Göckede (11), Bernhard Lehner (12), Mats Nilsson (13), Matthias Peichl (13), Oliver Sonnentag (14), Eeva-Stiina Tuittila (15), Torsten Sachs (16), Aram Kalhori (16), Masahito Ueyama (17), Zhen Zhang (1)
University of Maryland ESSIC (1), NASA GSFC (2), Woodwell Climate Research Center (3), NOAA ESRL (4), Lamont-Doherty Earth Observatory (5), Jet Propulsion Laboratory (6), Natural Resources Institute Finland (Luke), Latokartanonkaari 9, Helsinki, 00790, Finland (7), b.geos, Korneuburg, Austria (8), Department of Atmospheric and Oceanic Sciences, University of Wisconsin, Madison, WI 53706, USA (9), Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA (10), Max Planck Institute for Biogeochemistry, Jena, Germany (11), Department of Geography, McGill University, Montreal, QC H3A 0B9, Canada (12), Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden (13), Département de géographie, Université de Montréal, Montréal, QC, Canada (14), University of Eastern Finland, School of Forest Sciences, Joensuu, Finland (15), GFZ German Research Centre for Geosciences, Potsdam, Germany (16), Graduate School of Agriculture, Osaka Metropolitan University, Japan (17)
Wetlands are the largest natural source of methane (CH4) emissions globally. Northern wetlands (>45° N), accounting for 42% of global wetland area, are increasingly vulnerable to carbon loss, especially as CH4 emissions may accelerate under intensified high-latitude warming. However, the magnitude and spatial patterns of high-latitude CH4 emissions remain relatively uncertain. Here we present estimates of daily CH4 fluxes obtained using a new machine learning-based wetland CH4 upscaling framework (WetCH4) that applies the most complete database of eddy covariance (EC) observations available to date, and satellite remote sensing informed observations of environmental conditions at 10-km resolution. The most important predictor variables included near-surface soil temperatures (top 40 cm), vegetation reflectance, and soil moisture. Our results, modeled from 138 site-years across 26 sites, had relatively strong predictive skill with a mean R2 of 0.46 and 0.62 and a mean absolute error (MAE) of 23 nmol m-2 s-1 and 21 nmol m-2 s-1 for daily and monthly fluxes, respectively. Based on the model results, we estimated an annual average of 20.8 ±2.1 Tg CH4 yr-1 for the northern wetland region (2016-2022) and total budgets ranged from 13.7 - 44.1 Tg CH4 yr-1, depending on wetland map extents. Although 86% of the estimated CH4 budget occurred during the May-October period, a considerable amount (1.4 ±0.2 Tg CH4) occurred during winter. Regionally, the West Siberian wetlands accounted for a majority (51%) of the interannual variation in domain CH4 emissions. Significant issues with data coverage remain, with only 23% of the sites observing year-round and most of the data from 11 wetland sites in Alaska and 10 bog/fen sites in Canada and Fennoscandia, and in general, Western Siberian Lowlands are underrepresented by EC CH4 sites. Our results provide high spatiotemporal information on the wetland emissions in the high-latitude carbon cycle and possible responses to climate change. Continued, all-season tower observations and improved soil moisture products are needed for future improvement of CH4 upscaling. The dataset can be found at https://doi.org/10.5281/zenodo.10802154 (Ying et al., 2024).
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poster]
Wetlands are the largest natural source of methane (CH4) emissions globally. Northern wetlands (>45° N), accounting for 42% of global wetland area, are increasingly vulnerable to carbon loss, especially as CH4 emissions may accelerate under intensified high-latitude warming. However, the magnitude and spatial patterns of high-latitude CH4 emissions remain relatively uncertain. Here we present estimates of daily CH4 fluxes obtained using a new machine learning-based wetland CH4 upscaling framework (WetCH4) that applies the most complete database of eddy covariance (EC) observations available to date, and satellite remote sensing informed observations of environmental conditions at 10-km resolution. The most important predictor variables included near-surface soil temperatures (top 40 cm), vegetation reflectance, and soil moisture. Our results, modeled from 138 site-years across 26 sites, had relatively strong predictive skill with a mean R2 of 0.46 and 0.62 and a mean absolute error (MAE) of 23 nmol m-2 s-1 and 21 nmol m-2 s-1 for daily and monthly fluxes, respectively. Based on the model results, we estimated an annual average of 20.8 ±2.1 Tg CH4 yr-1 for the northern wetland region (2016-2022) and total budgets ranged from 13.7 - 44.1 Tg CH4 yr-1, depending on wetland map extents. Although 86% of the estimated CH4 budget occurred during the May-October period, a considerable amount (1.4 ±0.2 Tg CH4) occurred during winter. Regionally, the West Siberian wetlands accounted for a majority (51%) of the interannual variation in domain CH4 emissions. Significant issues with data coverage remain, with only 23% of the sites observing year-round and most of the data from 11 wetland sites in Alaska and 10 bog/fen sites in Canada and Fennoscandia, and in general, Western Siberian Lowlands are underrepresented by EC CH4 sites. Our results provide high spatiotemporal information on the wetland emissions in the high-latitude carbon cycle and possible responses to climate change. Continued, all-season tower observations and improved soil moisture products are needed for future improvement of CH4 upscaling. The dataset can be found at https://doi.org/10.5281/zenodo.10802154 (Ying et al., 2024).