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Enhanced methane emissions from tropical wetlands during the 2011 La Ni ñ a

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ABSTRACT

Year-to-year variations in the atmospheric methane (CH4) growth rate show significant correlation with climatic drivers. The second half of 2010 and the first half of 2011 experienced the strongest La Niña since the early 1980s, when global surface networks started monitoring atmospheric CH4 mole fractions. We use these surface measurements, retrievals of column-averaged CH4 mole fractions from GOSAT, new wetland inundation estimates, and atmospheric δ13C-CH4 measurements to estimate the impact of this strong La Niña on the global atmospheric CH4 budget. By performing atmospheric inversions, we find evidence of an increase in tropical CH4 emissions of ∼6–9 TgCH4 yr−1 during this event. Stable isotope data suggest that biogenic sources are the cause of this emission increase. We find a simultaneous expansion of wetland area, driven by the excess precipitation over the Tropical continents during the La Niña. Two process-based wetland models predict increases in wetland area consistent with observationally-constrained values, but substantially smaller per-area CH4 emissions, highlighting the need for improvements in such models. Overall, tropical wetland emissions during the strong La Niña were at least by 5% larger than the long-term mean.

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(a) Detrended and smoothened CH4 surface emissions estimates from TM5-4DVAR for the same regions as in Fig. 1. The variability of GFED4s biomass burning emissions has been subtracted. (b) δ13C-CH4 measurements54 corrected for the influence of transport using a meteorology-only TM5 simulation of δ13C-CH432. The light shaded regions represent the ±1σ uncertainty of the respective time series.
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f2: (a) Detrended and smoothened CH4 surface emissions estimates from TM5-4DVAR for the same regions as in Fig. 1. The variability of GFED4s biomass burning emissions has been subtracted. (b) δ13C-CH4 measurements54 corrected for the influence of transport using a meteorology-only TM5 simulation of δ13C-CH432. The light shaded regions represent the ±1σ uncertainty of the respective time series.

Mentions: The origin of an atmospheric CH4 anomaly can be identified using CH4 stable isotope measurements. We look at measurements of 13C/12C in CH4 (expressed in δ-notation as δ13C-CH4) analyzed by INSTAAR in samples from the NOAA-ESRL (ref. 30, see Fig. 2b). δ13C-CH4 of atmospheric CH4 (global average in 2009=−47.14‰) is controlled by the relative contribution from different source types with distinct isotopic signatures. The mean isotopic signatures of the biogenic category is ∼ −60‰ (includes wetlands, agriculture, waste), for the thermogenic category it is ∼ −37‰ (includes fossil-fuels) and for pyrogenic category it is ∼ −22‰ (includes biomass burning)31. To account for impact of meteorological variability on δ13C-CH4, a meteorology simulation of δ13C-CH4 was performed using TM532.


Enhanced methane emissions from tropical wetlands during the 2011 La Ni ñ a
(a) Detrended and smoothened CH4 surface emissions estimates from TM5-4DVAR for the same regions as in Fig. 1. The variability of GFED4s biomass burning emissions has been subtracted. (b) δ13C-CH4 measurements54 corrected for the influence of transport using a meteorology-only TM5 simulation of δ13C-CH432. The light shaded regions represent the ±1σ uncertainty of the respective time series.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5385533&req=5

f2: (a) Detrended and smoothened CH4 surface emissions estimates from TM5-4DVAR for the same regions as in Fig. 1. The variability of GFED4s biomass burning emissions has been subtracted. (b) δ13C-CH4 measurements54 corrected for the influence of transport using a meteorology-only TM5 simulation of δ13C-CH432. The light shaded regions represent the ±1σ uncertainty of the respective time series.
Mentions: The origin of an atmospheric CH4 anomaly can be identified using CH4 stable isotope measurements. We look at measurements of 13C/12C in CH4 (expressed in δ-notation as δ13C-CH4) analyzed by INSTAAR in samples from the NOAA-ESRL (ref. 30, see Fig. 2b). δ13C-CH4 of atmospheric CH4 (global average in 2009=−47.14‰) is controlled by the relative contribution from different source types with distinct isotopic signatures. The mean isotopic signatures of the biogenic category is ∼ −60‰ (includes wetlands, agriculture, waste), for the thermogenic category it is ∼ −37‰ (includes fossil-fuels) and for pyrogenic category it is ∼ −22‰ (includes biomass burning)31. To account for impact of meteorological variability on δ13C-CH4, a meteorology simulation of δ13C-CH4 was performed using TM532.

View Article: PubMed Central - PubMed

ABSTRACT

Year-to-year variations in the atmospheric methane (CH4) growth rate show significant correlation with climatic drivers. The second half of 2010 and the first half of 2011 experienced the strongest La Niña since the early 1980s, when global surface networks started monitoring atmospheric CH4 mole fractions. We use these surface measurements, retrievals of column-averaged CH4 mole fractions from GOSAT, new wetland inundation estimates, and atmospheric δ13C-CH4 measurements to estimate the impact of this strong La Niña on the global atmospheric CH4 budget. By performing atmospheric inversions, we find evidence of an increase in tropical CH4 emissions of ∼6–9 TgCH4 yr−1 during this event. Stable isotope data suggest that biogenic sources are the cause of this emission increase. We find a simultaneous expansion of wetland area, driven by the excess precipitation over the Tropical continents during the La Niña. Two process-based wetland models predict increases in wetland area consistent with observationally-constrained values, but substantially smaller per-area CH4 emissions, highlighting the need for improvements in such models. Overall, tropical wetland emissions during the strong La Niña were at least by 5% larger than the long-term mean.

No MeSH data available.


Related in: MedlinePlus