Journal
GLOBAL CHANGE BIOLOGY
Volume 24, Issue 8, Pages 3331-3343Publisher
WILEY
DOI: 10.1111/gcb.14137
Keywords
boreal; methane; model-data comparison; nongrowing season emissions; peatlands; synthesis; tundra; wetlands
Funding
- Biotieteiden ja Ympariston Tutkimuksen Toimikunta
- Division of Arctic Sciences [ARC-1304823]
- Jet Propulsion Laboratory [NNH14ZDA001N-CMS]
- EU JPI [70426, 291691]
- Finnish Academy of Sciences CAPTURE Project
- National Science Foundation P2C2 Program
- COUP
- NASA Earth Sciences grant [NNH14ZDA001N-CMS]
- Directorate For Geosciences
- Office of Polar Programs (OPP) [1304823] Funding Source: National Science Foundation
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Wetlands are the single largest natural source of atmospheric methane (CH4), a greenhouse gas, and occur extensively in the northern hemisphere. Large discrepancies remain between bottom-up and top-down estimates of northern CH4 emissions. To explore whether these discrepancies are due to poor representation of nongrowing season CH4 emissions, we synthesized nongrowing season and annual CH4 flux measurements from temperate, boreal, and tundra wetlands and uplands. Median nongrowing season wetland emissions ranged from 0.9 g/m(2) in bogs to 5.2 g/m(2) in marshes and were dependent on moisture, vegetation, and permafrost. Annual wetland emissions ranged from 0.9 gm(-2) year(-1) in tundra bogs to 78 gm(-2)year(-1) in temperate marshes. Uplands varied from CH4 sinks to CH4 sources with a median annual flux of 0.0 +/- 0.2 gm(-2)year(-1). The measured fraction of annual CH4 emissions during the nongrowing season (observed: 13% to 47%) was significantly larger than that was predicted by two process-based model ensembles, especially between 40 degrees and 60 degrees N (modeled: 4% to 17%). Constraining the model ensembles with the measured nongrowing fraction increased total nongrowing season and annual CH4 emissions. Using this constraint, the modeled nongrowing season wetland CH4 flux from >40 degrees north was 6.1 +/- 1.5 Tg/year, three times greater than the nongrowing season emissions of the unconstrained model ensemble. The annual wetland CH4 flux was 37 +/- 7 Tg/year from the data-constrained model ensemble, 25% larger than the unconstrained ensemble. Considering nongrowing season processes is critical for accurately estimating CH4 emissions from high-latitude ecosystems, and necessary for constraining the role of wetland emissions in a warming climate.
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