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WetCH4: A Machine Learning-based Upscaling of Methane Fluxes of Northern Wetlands during 2016–2022.
- Source :
- Earth System Science Data Discussions; 4/3/2024, p1-45, 45p
- Publication Year :
- 2024
-
Abstract
- Wetlands are the largest natural source of methane (CH<subscript>4</subscript>) emissions globally. Northern wetlands (>45° N), accounting for 42 % of global wetland area, are increasingly vulnerable to carbon loss, especially as CH<subscript>4</subscript> emissions may accelerate under intensified high-latitude warming. However, the magnitude and spatial patterns of high-latitude CH<subscript>4</subscript> emissions remain relatively uncertain. Here we present estimates of daily CH<subscript>4</subscript> fluxes obtained using a new machine learning-based wetland CH<subscript>4</subscript> upscaling framework (WetCH<subscript>4</subscript>) 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 R<superscript>2</superscript> of 0.46 and 0.62 and a mean absolute error (MAE) of 23 nmol m<superscript>-2</superscript> s<superscript>-1</superscript> and 21 nmol m<superscript>-2</superscript> s<superscript>-1</superscript> for daily and monthly fluxes, respectively. Based on the model results, we estimated an annual average of 20.8 ±2.1 Tg CH<subscript>4</subscript> yr<superscript>-1</superscript> for the northern wetland region (2016–2022) and total budgets ranged from 13.7–44.1 Tg CH<subscript>4</subscript> yr<superscript>-1</superscript>, depending on wetland map extents. Although 86 % of the estimated CH<subscript>4</subscript> budget occurred during the May–October period, a considerable amount (1.4 ±0.2 Tg CH<subscript>4</subscript>) occurred during winter. Regionally, the West Siberian wetlands accounted for a majority (51 %) of the interannual variation in domain CH<subscript>4</subscript> 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 CH<subscript>4</subscript> 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 CH<subscript>4</subscript> upscaling. The dataset can be found at https://doi.org/10.5281/zenodo.10802154 (Ying et al., 2024). [ABSTRACT FROM AUTHOR]
- Subjects :
- WETLANDS
INDEPENDENT variables
CARBON cycle
METHANE
SOIL temperature
BUDGET
Subjects
Details
- Language :
- English
- ISSN :
- 18663591
- Database :
- Complementary Index
- Journal :
- Earth System Science Data Discussions
- Publication Type :
- Academic Journal
- Accession number :
- 176410258
- Full Text :
- https://doi.org/10.5194/essd-2024-84