HR: 1340h
AN: A33E-1635    [Abstracts]
TI: A Model Study of the Sulfur Cycle at the Last Glacial Maximum
AU: Castebrunet, H
AF: Laboratoire de Glaciologie et Géophysique de l'Environnement, BP 96, St Martin d'Hères, 38 402, France
AU: * Martinerie, P
EM: patricia@lgge.obs.ujf-grenoble.fr
AF: Laboratoire de Glaciologie et Géophysique de l'Environnement, BP 96, St Martin d'Hères, 38 402, France
AU: Genthon, C
AF: Laboratoire de Glaciologie et Géophysique de l'Environnement, BP 96, St Martin d'Hères, 38 402, France
AB: The mid and high-southern latitudes are still marginally affected by anthropogenic sulfur emissions. Sulfur aerosols are well-known for their radiative impact, and thus interact with climate. Climate can in turn affect atmospheric sulfur sources, distribution and chemistry. Antarctic ice cores provide information on the evolution of climate and sulfur deposition at the surface of the ice sheet at glacial-interglacial time scales. In this sudy, an Atmospheric General Circulation Model (AGCM) was developed and used towards a better understanding of the atmospheric sulfur cycle in antarctic and sub-antarctic regions. Ice core data are used to validate model results under glacial climate conditions. The AGCM has been coupled to a sulfur chemistry module: the LMD-ZTSulfur model, version 4. An update of both the physical and chemical parts of the model was first performed. The impact of the changes on modelled sulfur cycle are evaluated for modern climate. Boundary conditions were adapted to simulate the atmospheric circulation and sulfur cycle at the Last Glacial Maximum, approximately 20,000 years ago. In the model, sulfur is found to be highly sensitive to antarctic sea-ice coverage, which is still poorly known during the ice age. An original dataset of ice-age sea-ice coverage was developed. Its impact on the oceanic emissions of dimethyl sulfide, the main precursor of sulfur aerosols at high- southern latitudes, is discussed. Using the same oceanic sulfur reservoirs as for present day climate, the model broadly reproduces the glacial deposits of sulfur aerosols on the Antarctic plateau, suggesting little impact of climate on oceanic sulfur production in the Antarctic region. Sensitivity tests were carried out in order to discuss major uncertainties and difficulties in understanding the natural atmospheric sulfur budget and its past variations with climate.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0724 Ice cores (4932)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting