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| Titel |
Drivers of diel and regional variations of halocarbon emissions from the tropical North East Atlantic |
| VerfasserIn |
H. Hepach, B. Quack, F. Ziska, S. Fuhlbrügge, E. L. Atlas, K. Krüger, I. Peeken, D. W. R. Wallace |
| 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 ; 14, no. 3 ; Nr. 14, no. 3 (2014-02-03), S.1255-1275 |
| Datensatznummer |
250118351
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| Publikation (Nr.) |
 copernicus.org/acp-14-1255-2014.pdf |
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| Zusammenfassung |
| Methyl iodide (CH3I), bromoform (CHBr3) and dibromomethane
(CH2Br2), which are produced naturally in the oceans, take part in
ozone chemistry both in the troposphere and the stratosphere. The
significance of oceanic upwelling regions for emissions of these trace gases
in the global context is still uncertain although they have been identified
as important source regions. To better quantify the role of upwelling areas
in current and future climate, this paper analyzes major factors that
influenced halocarbon emissions from the tropical North East Atlantic
including the Mauritanian upwelling during the DRIVE expedition. Diel and
regional variability of oceanic and atmospheric CH3I, CHBr3 and
CH2Br2 was determined along with biological and physical parameters at
six 24 h-stations. Low oceanic concentrations of CH3I from
0.1–5.4 pmol L−1 were equally distributed throughout the
investigation area. CHBr3 and CH2Br2 from 1.0 to
42.4 pmol L−1 and to 9.4 pmol L−1, respectively were measured
with maximum concentrations close to the Mauritanian coast. Atmospheric
CH3I, CHBr3, and CH2Br2 of up to 3.3, 8.9, and 3.1 ppt,
respectively were detected above the upwelling, as well as up to 1.8, 12.8,
and 2.2 ppt at the Cape Verdean coast. While diel variability in CH3I
emissions could be mainly ascribed to oceanic non-biological production, no
main driver was identified for its emissions over the entire study region. In
contrast, biological parameters showed the greatest influence on the regional
distribution of sea-to-air fluxes of bromocarbons. The diel impact of wind
speed on bromocarbon emissions increased with decreasing distance to the
coast. The height of the marine atmospheric boundary layer (MABL) influenced
halocarbon emissions via its influence on atmospheric mixing ratios. Oceanic
and atmospheric halocarbons correlated well in the study region, and in
combination with high oceanic CH3I, CHBr3 and CH2Br2
concentrations, local hot spots of atmospheric halocarbons could solely be
explained by marine sources. This conclusion is in contrast to previous
studies that hypothesized elevated atmospheric halocarbons above the eastern
tropical Atlantic to be mainly originated from the West-African continent. |
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