Title A three-dimensional model study of methanesulphonic acid to non sea salt sulphate ratio at mid and high-southern latitudes
Author Castebrunet, H.; Martinerie, P.; Genthon, C.; Cosme, E.
Author Affil Castebrunet, H., Université Joseph Fourier-Grenoble I, Laboratoire de Glaciologie et Géophysique de l'Environnement, Saint Martin d'Heres, France. Other: Institut National Polytechnique, France
Source Atmospheric Chemistry and Physics, 9(24), p.9449-9469, . Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1680- 7316
Publication Date 2009
Notes In English. Includes appendix, http://www.atmos-chem- phys.net/9/9449/2009/acp-9-9449-2009- supplement.pdf; published in Atmospheric Chemistry and Physics Discussions: 13 July 2009, http://www.atmos-chem-phys- discuss.net/9/14995/2009/acpd-9-14995- 2009.html ; accessed in May, 2011. 91 refs. Ant. Acc. No: 91583. GeoRef Acc. No: 310483
Index Terms firn; geochemistry; hydrocarbons; ice; ozone; snow; Indian Ocean Islands--Amsterdam Island; Antarctica--Dome C; Antarctica--South Pole; aliphatic hydrocarbons; alkanes; Amsterdam Island; Antarctica; atmosphere; atmospheric transport; chemical reactions; dimethyl sulfoxide; Dome C; Dumont d'Urville; general circulation models; Halley Bay; ice cores; Indian Ocean Islands; methane; methanesulfonic acid; organic compounds; oxidation; sea salt; seasonal variations; South Pole; sulfates; sulfur; three- dimensional models; transport; Wilkes Land
Abstract The Antarctic and sub-Antarctic methanesulphonic acid (MSA) to non sea salt sulphate (nssSO4) ratio is simulated with the Laboratoire de Meteorologie Dynamique Atmospheric General Circulation Model including an atmospheric sulphur chemistry module. Spatial variations of the MSA/nssSO4 ratio in different regions have been suggested to be mostly dependent on temperature or sulphur source contributions. Its past variations in ice cores have been interpreted as related to the DMS precursor source location. Our model results are compared with available field measurements in the Antarctic and sub-Antarctic regions. This suggests that the MSA/nssSO4 ratio in the extra-tropical south hemisphere is mostly dependent on the relative importance of various DMS oxidation pathways. In order to evaluate the effect of a rapid conversion of dimethyl sulphoxide (DMSO) into MSA, not implemented in the model, the MSA+DMSO to nssSO4 ratio is also discussed. Using this modified ratio, the model mostly captures the seasonal variations of MSA/nssSO4 at mid and high-southern latitudes. In addition, the model qualitatively reproduces the bell shaped meridional variations of the ratio, which is highly dependent on the adopted relative reaction rates for the DMS+OH addition and abstraction pathways, and on the assumed reaction products of the MSIA+OH reaction. MSA/nssSO4 ratio in Antarctic snow is fairly well reproduced except at the most inland sites characterized with very low snow accumulation rates. Our results also suggest that atmospheric chemistry plays an important role in the observed decrease of the ratio in snow between coastal regions and central Antarctica. The still insufficient understanding of the DMS oxidation scheme limits our ability to model the MSA/nssSO4 ratio. Specifically, reaction products of the MSIA+OH reaction should be better quantified, and the impact of a fast DMSO conversion to MSA in spring to fall over Antarctica should be evaluated. A better understanding of BrO source processes is needed in order to include DMS+BrO chemistry in global models. Completing the observations of DMS, BrO and MSA at Halley Bay with DMSO measurements would better constrain the role of BrO in DMS oxidation. Direct measurements of MSA and nssSO4 dry deposition velocities on Antarctic snow would improve our ability to model MSA and nssSO4 in ice cores.
URL http://www.atmos-chem-phys.net/9/9449/2009/acp-9-9449-2009.pdf
Publication Type journal article
Record ID 65007116