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| Titel |
The interpretation of spikes and trends in concentration of nitrate in polar ice cores, based on evidence from snow and atmospheric measurements |
| VerfasserIn |
E. W. Wolff, A. E. Jones, S. J.-B. Bauguitte, R. A. Salmon |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 18 ; Nr. 8, no. 18 (2008-09-24), S.5627-5634 |
| Datensatznummer |
250006389
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| Publikation (Nr.) |
 copernicus.org/acp-8-5627-2008.pdf |
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| Zusammenfassung |
| Nitrate is frequently measured in ice cores, but its interpretation remains
immature. Using daily snow surface concentrations of nitrate at Halley
(Antarctica) for 2004–2005, we show that sharp spikes (>factor 2) in
nitrate concentration can occur from day to day. Some of these spikes will
be preserved in ice cores. Many of them are associated with sharp increases
in the concentration of sea salt in the snow. There is also a close
association between the concentrations of aerosol nitrate and sea salt
aerosol. This evidence is consistent with many of the spikes in deposited
nitrate being due to the conversion or trapping of gas-phase nitrate, i.e. to
enhanced deposition rather than enhanced atmospheric concentrations of
NOy. Previously, sharp spikes in nitrate concentration (with
concentration increases of up to a factor 4 seen in probably just one
snowfall) have been assigned to sharp production events such as solar proton
events (SPEs). We find that it is unlikely that SPEs can produce spikes of
the kind seen. Taken together with our evidence that such spikes can be
produced depositionally, we find that it is not possible to track past SPEs
without carrying out a new multi-site and multi-analyte programme. Seasonal
and interannual trends in nitrate concentration in cores from any single
site cannot be interpreted in terms of production changes until the
recycling of nitrate from central Antarctica to coastal Antarctica is better
quantified. It might be possible to assess the interannual input of NOy
to the Antarctic lower troposphere by using a network of cores to estimate
variability in the total annual deposition across the continent (which we
estimate to be 9±2×107kg/a – as NO3−), but it will
first have to be established that the outflow across the coast can be ignored. |
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