title: Seasonality and interannual variability of CH4fluxes from the eastern Amazon Basin inferred from atmospheric mole fraction profiles.
abstract: The Amazon Basin is an important region for global CH4emissions. It hosts the largest area of humid tropical forests, and around 20% of this area is seasonally flooded. In a warming climate it is possible that CH4emissions from the Amazon will increase both as a result of increased temperatures and precipitation. To examine if there are indications of first signs of such changes we present here a 13 year (2000-2013) record of regularly measured vertical CH4mole fraction profiles above the eastern Brazilian Amazon, sensitive to fluxes from the region upwind of Santarém (SAN), between SAN and the Atlantic coast. Using a simple mass balance approach, we find substantial CH4emissions with an annual average flux of 52.8 ± 6.8 mg CH4m-2d-1over an area of approximately 1 × 106km2. Fluxes are highest in two periods of the year: in the beginning of the wet season and during the dry season. Using a CO:CH4emission factor estimated from the profile data, we estimated a contribution of biomass burning of around 15% to the total flux in the dry season, indicating that biogenic emissions dominate the CH4flux. This 13 year record shows that CH4emissions upwind of SAN varied over the years, with highest emissions in 2008 (around 25% higher than in 2007), mainly during the wet season, representing 19% of the observed global increase in this year.
authors.affiliation: Atmospheric Chemistry Laboratory, Instituto de Pesquisas Energéticas e Nucleares Comissão Nacional de Energia Nuclear São Paulo Brazil.
authors.forename: Luana S
authors.initials: LS
authors.lastname: Basso
authors.affiliation: Atmospheric Chemistry Laboratory, Instituto de Pesquisas Energéticas e Nucleares Comissão Nacional de Energia Nuclear São Paulo Brazil.
authors.forename: Luciana V
authors.initials: LV
authors.lastname: Gatti
authors.affiliation: School of Geography University of Leeds Leeds UK.
authors.forename: Manuel
authors.initials: M
authors.lastname: Gloor
authors.affiliation: Global Monitoring Division, Earth System Research Laboratory National Oceanic and Atmospheric Administration Boulder Colorado USA.
authors.forename: John B
authors.initials: JB
authors.lastname: Miller
authors.affiliation: Atmospheric Chemistry Laboratory, Instituto de Pesquisas Energéticas e Nucleares Comissão Nacional de Energia Nuclear São Paulo Brazil.
authors.forename: Lucas G
authors.initials: LG
authors.lastname: Domingues
authors.affiliation: Atmospheric Chemistry Laboratory, Instituto de Pesquisas Energéticas e Nucleares Comissão Nacional de Energia Nuclear São Paulo Brazil.
authors.forename: Caio S C
authors.initials: CS
authors.lastname: Correia
authors.affiliation: Atmospheric Chemistry Laboratory, Instituto de Pesquisas Energéticas e Nucleares Comissão Nacional de Energia Nuclear São Paulo Brazil.
authors.forename: Viviane F
authors.initials: VF
authors.lastname: Borges
keywords: Amazon; greenhouse gas; methane; methane flux