Clim. Past Discuss., 6, 1991-2004, 2010
www.clim-past-discuss.net/6/1991/2010/
doi:10.5194/cpd-6-1991-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP.
Early last glacial maximum in the Southern Central Andes reveals northward shift of the westerlies at ~39 ka
R. Zech1,*, J. Zech1, C. Kull1, P. W. Kubik2, and H. Veit1
1Geographical Institute, University of Bern, Bern, Switzerland
2Ion Beam Physics, ETH Zurich, Zurich, Switzerland
*now at: Geological Institute, ETH Zurich, Zurich, Switzerland

Abstract. The latitudinal position of the southern westerlies has been suggested to be a key parameter for the climate on Earth. According to the general notion, the southern westerlies were shifted equatorward during the global Last Glacial Maximum (LGM: ~24–18 ka), resulting in reduced deep ocean ventilation, accumulation of "old dissolved carbon", and low atmospheric CO2 concentrations. In order to test this notion, we applied surface exposure dating on moraines in the Southern Central Andes, where glacial mass balances are particularly sensitive to changes in precipitation, i.e. to the latitudinal position of the westerlies. Our results provide robust evidence that the maximum glaciation occurred already at ~39 ka, significantly predating the global LGM. This questions the role of the westerlies for atmospheric CO2, and it highlights our limited understanding of the forcings of atmospheric circulation.

Citation: Zech, R., Zech, J., Kull, C., Kubik, P. W., and Veit, H.: Early last glacial maximum in the Southern Central Andes reveals northward shift of the westerlies at ~39 ka, Clim. Past Discuss., 6, 1991-2004, doi:10.5194/cpd-6-1991-2010, 2010.
 
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