Underway water measurements of halocarbons during POSEIDON cruise POS399 in June 2010


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 meteorological parameters at six 24 h-stations. Low oceanic concentrations of CH3I from 0.1-5.4 pmol/L were equally distributed throughout the investigation area. CHBr3 of 1.0-42.4 pmol/L and CH2Br2 of 1.0-9.4 pmol/L were measured with maximum concentrations close to the Mauritanian coast. Atmospheric mixing rations of CH3I of up to 3.3, CHBr3 to 8.9 and CH2Br2 to 3.1 ppt above the upwelling and 1.8, 12.8, respectively 2.2 ppt at a Cape Verdean coast were detected during the campaign. While diel variability in CH3I emissions could be mainly ascribed to oceanic non-biological production, no main driver was identified for its emissions in the entire study region. In contrast, oceanic bromocarbons resulted from biogenic sources which were identified as regional drivers of their sea-to-air fluxes. 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) was determined as an additional factor influencing halocarbon emissions. 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 with previous studies that hypothesized the occurrence of elevated atmospheric halocarbons over the eastern tropical Atlantic mainly originating from the West-African continent.

Supplement to: Hepach, Helmke; Quack, Birgit; Ziska, Franziska; Fuhlbruegge, Steffen; Atlas, Elliot L; Krüger, Kirstin; Peeken, Ilka; Wallace, Douglas WR (2014): Drivers of diel and regional variations of halocarbon emissions from the tropical North East Atlantic. Atmospheric Chemistry and Physics, 14(3), 1255-1275

DOI https://doi.org/10.1594/PANGAEA.777300
Related Identifier IsSupplementTo https://doi.org/10.5194/acp-14-1255-2014
Related Identifier References https://doi.org/10.3289/ifm-geomar_rep_48_2011
Related Identifier References https://doi.org/10.1594/PANGAEA.855314
Related Identifier References https://doi.org/10.1594/PANGAEA.855334
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.777300
Creator Hepach, Helmke (ORCID: 0000-0002-4939-590X); Quack, Birgit; Ziska, Franziska; Fuhlbruegge, Steffen; Atlas, Elliot L ORCID logo; Krüger, Kirstin ORCID logo; Peeken, Ilka ORCID logo; Wallace, Douglas WR
Publisher PANGAEA
Publication Year 2014
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Resource Type Supplementary Dataset; Dataset
Format text/tab-separated-values
Size 1540 data points
Discipline Earth System Research
Spatial Coverage (-24.309W, 17.594S, -9.730E, 39.438N); Cape Verde
Temporal Coverage Begin 2010-06-03T22:45:00Z
Temporal Coverage End 2010-06-23T06:05:00Z