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| Titel |
Interrogating trees as archives of sulphur deposition |
| VerfasserIn |
P. M. Wynn, N. J. Loader, I. J. Fairchild |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060813
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| Zusammenfassung |
| A principal driver of climatic variability over the past 1,000 years and essential forcing
mechanism for climate, are the changes in atmospheric composition resulting from sulphur
aerosols. Natural and anthropogenic aerosols released into the atmosphere disrupt the
radiative balance through backscattering and absorption of incoming solar radiation and
increase cloud albedo by acting as condensation nuclei. Understanding the impact
of sulphur emissions upon climate beyond the last few hundred years however is
not straightforward and natural archives of environmental information must be
explored. Tree-rings represent one such archive as they are widely distributed and
preserve environmental information within a precisely dateable, annually resolved
timescale.
Until recently the sulphur contained within tree-rings has largely remained beyond the
reach of environmental scientists and climate modelers owing to difficulties associated with
the extraction of a robust signal and uncertainties regarding post-depositional mobility. Our
recent work using synchrotron radiation has established that the majority of non-labile
sulphur in two conifer species is preserved within the cellular structure of the woody tissue
after uptake and demonstrates an increasing trend in sulphur concentration during the 20th
century and during known volcanic events. Due to the clear isotopic distinction between
marine (+21), geological (+10 to +30), atmospheric pollution (-3 to +9 ) and volcanic sources
of sulphur (0 to +5), isotopic ratios provide a diagnostic tool with which changes in the
source of atmospheric sulphur can be detected in a more reliable fashion than concentration
alone. Sulphur isotopes should thereby provide a fingerprint of short lived events including
volcanic activity when extracted at high resolution and in conjunction with high resolution S
concentrations defining the event. Here we present methodologies associated with
extracting the sulphur isotopic signal from tree-rings using both elemental analyser
isotope ratio mass spectrometry and ion probe technology. Preliminary data indicate
success at extracting the sulphur isotopic signal from woody tissues at 2-3 year
resolution. In conjunction with analytical developments in ion probe technology, high
resolution records of localised sulphur forcing from tree-ring archives, including
volcanic activity, no longer seem too far beyond the reach of climate scientists. |
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