Journal
GLOBAL BIOGEOCHEMICAL CYCLES
Volume 30, Issue 3, Pages 400-420Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2015GB005300
Keywords
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Funding
- UK Natural Environment Research Council (NERC)
- National Centre for Earth Observation (NCEO)
- NERC Consortiumgrants for AMAZONICA [NE/F005806/1]
- Amazon hydrological cycle [NE/K01353X/1]
- EU 7th Framework GEOCARBON project grant [283080]
- CNPq
- FAPESP
- CIRES
- NOAA/ESRL
- CAPES
- NOAA Climate Program Office's Atmospheric Chemistry, Carbon Cycle, and Climate (AC4) program
- Royal Society Wolfson Merit Award
- NERC [NE/N015657/1, nceo020005, NE/F005806/1, NE/J016233/1, nceo020004] Funding Source: UKRI
- Natural Environment Research Council [nceo020004, NE/N015657/1, NE/F005806/1, NE/J016233/1, nceo020005] Funding Source: researchfish
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We present an assessment of methane (CH4) atmospheric concentrations over the Amazon Basin for 2010 and 2011 using a 3-D atmospheric chemical transport model, two wetland emission models, and new observations made during biweekly flights made over four locations within the basin. We attempt to constrain basin-wide CH4 emissions using the observations, and since 2010 was an unusually dry year, we assess the effect of this drought on Amazonian methane emissions. We find that South American emissions contribute up to 150 ppb to concentrations at the sites, mainly originating from within the basin. Our atmospheric model simulations agree reasonably well with measurements at three of the locations (0.28 <= r(2) <= 0.63, mean bias <= 9.5 ppb). Attempts to improve the simulated background CH4 concentration through analysis of simulated and observed sulphur hexafluoride concentrations do not improve the model performance, however. Through minimisation of seasonal biases between the simulated and observed atmospheric concentrations, we scale our prior emission inventories to derive total basin-wide methane emissions of 36.5-41.1 Tg(CH4)/yr in 2010 and 31.6-38.8 Tg(CH4)/yr in 2011. These totals suggest that the Amazon contributes significantly (up to 7%) to global CH4 emissions. Our analysis indicates that factors other than precipitation, such as temperature variations or tree mortality, may have affected microbial emission rates. However, given the uncertainty of our emission estimates, we cannot say definitively whether the noncombustion emissions from the region were different in 2010 and 2011, despite contrasting meteorological conditions between the two years.
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