Atmospheric sulfur and climate changes : a modelling study at mid and high-southern latitudes.

• Main Author: Castebrunet, Hélène, Hc
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Joseph-Fourier - Grenoble I, Christophe Genthon([e-mail])
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2007
• Subjects: Sulfur; aerosols; Antarctica; CLAW hypotesis; Last Glacial Maximum; climate changes; Soufre; Aérosols; Antarctique; Hypothèse CLAW; Dernier Maximum Glaciaire; Climat; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Antarc*; Antarctic; Antarctique*; Ice Sheet; Sea ice
• Online Access: https://theses.hal.science/tel-00187947; https://theses.hal.science/tel-00187947/document; https://theses.hal.science/tel-00187947/file/these_castebrunet.pdf

The mid and high-southern latitudes are still marginally affected by anthropogenic sulfur emissions and the natural cycle of the atmospheric sulfur may still be observed. Sulfur aerosols are well-known for their radiative impact, and thus interact with climate. 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. The aim of this thesis is to develop and use modeling towards a better understanding of the atmospheric sulfur cycle in antarctic and sub-antarctic regions. An Atmospheric General Circulation Model (AGCM) coupled to a sulfur chemistry module is used: the LMD-ZT-Sulfur model, version 4. The model was first performed (update of both the physical and chemical parts of the model). Further, boundary conditions are 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 and its impact on the oceanic emissions of dimethyl sulfide, main precursor of sulfur aerosols at high-southern latitudes, is discussed. 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 to draw an up-to-date status of major uncertainties and difficulties facing future progress in understanding atmospheric sulfur and climate. Les moyennes et hautes latitudes Sud sont les seules régions du monde pour lesquelles le cycle naturel du soufre atmosphérique peut encore être observé sans perturbation anthropique majeure. Les aérosols soufrés sont reconnus pour leur effet radiatif et interagissent ainsi avec le climat. L'analyse des carottes de glace en Antarctique permet de connaître les variations des dépôts d'aérosols ...