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| Titel |
Methane fluxes in the high northern latitudes estimated using a Bayesian atmospheric inversion |
| VerfasserIn |
Rona Thompson, Andreas Stohl, Cathrine Lund Myhre, Motoki Sasakawa, Toshinobu Machida, Tuula Aalto, Edward Dlugokencky, Douglas Worthy, Andrey Skorokhod |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250131463
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| Publikation (Nr.) |
 EGU/EGU2016-11875.pdf |
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| Zusammenfassung |
| Methane (CH$_{\text_{4}}$) is the second most important anthropogenic greenhouse gas after CO$_{\text_{2}}$. Atmospheric CH$_{\text_{4}}$ increased from pre-industrial concentrations of around 850 ppb (parts-per-billion) to 1773 ppb in the late 1990s and then remained approximately stable until the mid 2000s. However, since 2006 atmospheric CH$_{\text_{4}}$ has begun to increase again. The reasons for the stabilization and subsequent increase are likely to be a combination of changes in anthropogenic emissions such as from fossil fuels, as well as natural wetland sources. While global atmospheric inversions indicate that natural wetland sources in the tropics and subtropics have contributed to the recent increase, land surface and ecosystem models generally indicate no increase in these sources. Another potential source for the change in CH$_{\text_{4}}$ concentration could be wetlands in the high northern latitudes, which comprise about 44\% of global wetland area. These latitudes are also undergoing rapid warming, which will impact wetland emissions of CH$_{\text_{4}}$.
We present CH$_{\text_{4}}$ fluxes for the high northern latitudes (>50$^{\circ}$N) from 2005 to 2012 estimated from a Bayesian atmospheric inversion. The inversion incorporates observations from 17 in-situ and 6 discrete-sample sites across North America and Northern Eurasia. Atmospheric transport is based on the Lagrangian particle dispersion model, FLEXPART, run with ECMWF meteorological analyses. Emissions were optimized monthly and on a spatial grid of variable resolution (from 1$^{\circ}$$\times$1$^{\circ}$ to 4$^{\circ}$$\times$4$^{\circ}$). Background concentrations were estimated by coupling FLEXPART to monthly global 2-D fields of CH$_{\text_{4}}$ concentration from a bivariate interpolation of smoothed data from the NOAA ESRL network. We estimate the total mean North American flux (>50$^{\circ}$N) to be 18 -- 27 Tg y$^{\text_{-1}}$, and the total mean Northern Eurasian flux (>50$^{\circ}$N) to be 55 -- 66 Tg y$^{\text_{-1}$}, both substantially higher than the prior (based on LPX-Bern for wetland and EDGAR-4.2FT2010 for anthropogenic fluxes). We also find a small trend in the wintertime fluxes in North America and North Eurasia, which may indicate an increase in anthropogenic emissions in both regions. |
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