Methane emission from high-latitude wetlands: Evaluating the impact of incorporating wetland types and the full suite of high-latitude methane fluxes
Abstract
Natural wetlands play an important role in the global methane cycle, contributing about 30% to total annual emissions. Results of modeling studies investigating the role of natural wetlands in the contemporary CH4 cycle reveal substantial differences in the seasonality, distribution and trends in emissions among models, limiting robust conclusions about the wetland contribution to atmospheric CH4 variations. Hundreds of flux measurements in wetland ecosystems confirm that fluxes are dependent on wetland type but very few wetland-methane models explicitly consider wetland types . In addition, the primary contributor to divergent model emissions is differences in wetland representation. Most models define 'wetlands' (or CH4-producing areas) using monthly inundation data that 1) include, but do not distinguish among, flooded wetlands, lakes, rivers, irrigated rice and other unidentified aquatic features, 2) fail to capture non-flooded wetlands which account for ~70% of the world's wetland areas and 3) provide no information about wetland type. Consequently, the majority of simulated emissions attributed to wetlands, especially in lake-rich high latitudes 1) primarily represent non-wetland emissions, 2) misplace spatial and temporal emissions of wetlands, and 3) conflate wetland and lake emissions such that their individual roles in the global methane cycle are not distinguishable.
We developed a new 0.25˚ wetland data set, mutually-exclusive of our lake data set , that identifies wetland types using a unique methane-centric classification system. We also classified ~800 wetland sites (Treat et al., 2018) where methane fluxes were measured with the same classification system. This pairing links, for the first time, methane fluxes for wetland types and the global distribution of those same wetlands. We report on a first estimate of methane emission from high-latitude wetlands ( >50˚N) together with mutually-exclusive lake emissions for the same region. We compare results to other estimates of high-latitude 'wetland' and lake emissions and analyze the impact of explicitly incorporating methane-relevant wetland types and all wetland flux observations on emission results.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B13J2419M
- Keywords:
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- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0490 Trace gases;
- BIOGEOSCIENCES;
- 0497 Wetlands;
- BIOGEOSCIENCES;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE