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| Titel |
Long-term observations of stable isotopes in atmospheric methane - how robust are the reported trends? |
| VerfasserIn |
Ingeborg Levin, Cordelia Veidt, Christian Poß, Renate Heinz, Bruce H. Vaughn, James W. C. White, Gordon Brailsford, Tony Bromley, Dave Lowe, Rebecca Fisher, David Lowry |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250058112
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| Zusammenfassung |
| Since more than a century, the atmospheric methane burden has been rising at variable rates,
mainly due to increasing emissions associated with human activities. But also climate-related
changes of natural methane sources and destruction processes most probably contributed to
the observed long term variability. Disentangling the causes responsible for the observed
growth rate pattern is an ongoing debate. Here, stable isotope measurements in
atmospheric and source methane, backed up by fractionation studies of its major sink
processes are thought to provide a valuable tool for understanding the global methane
budget and its inter-annual variations. However, the imprint of changing fluxes on the
isotope trends in the atmosphere are notoriously weak; therefore, precise and highly
consistent atmospheric observations are required if these tools shall be successfully
applied.
Only a small number of laboratories made the effort of monitoring atmospheric methane
isotopes in the last two decades, and this undertaking was particularly challenging as
internationally accepted standard reference material for methane isotope analyses have not
been available so far. Also, only few and mostly bi-lateral comparison experiments have been
conducted between the few laboratories performing these specialized methane isotope
analyses, and, in most cases, also not as an ongoing effort over the last two decades. This was
the main reason why it has not yet been possible to reliably combine data from different
observational networks, and, the interpretation of observed trends has not always been
consistent.
At this stage, we make a first attempt to compare available data sets of stable methane
isotope observations (δD-CH4 and δ13C-CH4) from the last two decades. As different
laboratories performed observations at the same sites, i.e. in Alert (Arctic, 82°N), at mid
northern latitudes at Niwot Ridge (40°N) or Mace Head (53°N) or in the well-mixed
Southern Hemisphere at Cape Grim (Tasmania, 41°S) and Baring Head (New Zealand,
41°S), but also at the Antarctic coast (Scott Base, 78°S, and Neumayer Station, 71°S), there
is even some potential to merge these different data sets. The main purpose of this
study is to compare the long-term trends observed by the different laboratories:
Only common trends can be assumed as robust, and will briefly be discussed in
terms of deciphering changes in the sources and sinks of atmospheric methane. |
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