Biogeosciences Discuss., 10, 9315-9343, 2013
© Author(s) 2013. 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 Biogeosciences (BG). Please refer to the corresponding final paper in BG.
Southern Hemisphere imprint for Indo–Asian summer monsoons during the last glacial period as revealed by Arabian Sea productivity records
T. Caley1,2, S. Zaragosi1, J. Bourget3, P. Martinez1, B. Malaizé1, F. Eynaud1, L. Rossignol1, T. Garlan4, and N. Ellouz-Zimmermann5
1Univ. Bordeaux, CNRS, EPOC, UMR5805, 33400 Talence, France
2Section Climate Change and Landscape Dynamics, Dept. of Earth Sciences, Vrije Universiteit Amsterdam, the Netherlands
3School of Earth and Environment, CPGCO2, University of Western Australia, 35 Stirling Highway, Crawley 6009, Australia
4Service Hydrographique et Océanographique de la Marine, Cellule Sédimentologie, 13 rue du Chatellier, BP30316 29603 Brest cedex, France
5IFPEN, 1 & 4 avenue de Bois Préau, 92852 Rueil-Malmaison, France

Abstract. The monsoon is one of the most important climatic phenomena: it promotes inter-hemispheric exchange of energy and affects the economical prosperity of several countries exposed to its seasonal seesaw. Previous studies in both the Indian and Asian monsoon systems have suggested a dominant north hemispheric (NH) control on summer monsoon dynamics at the scale of suborbital-millennial climatic changes, while the forcing/response of Indian and Asian monsoons at the orbital scale remains a matter of debate. Here nine marine sediment cores distributed across the whole Arabian Sea are used to build a regional surface marine productivity signal. The productivity signal is driven by the intensity of Indian summer monsoon winds. Results demonstrate the existence of an imprint of suborbital Southern Hemisphere (SH) temperature changes (i.e., Antarctica) on the Indian summer monsoon during the last glacial period, challenging the traditional and exclusive NH forcing hypothesis. Meanwhile, during the last deglaciation, the NH plays a more significant role. The δ18O signal recorded in the Asian monsoon speleothem records could be exported by winds from the Indian summer monsoon region, as recently proposed in modelling exercise, explaining the SH signature observed in Asian cave speleothems. Contrary to the view of a passive response of Indian and Asian monsoons to NH anomalies, the present results strongly suggest that the Indo–Asian summer monsoon plays an active role in amplifying millennial inter-hemispheric asymmetric patterns. Additionally, this study helps to decipher the observed differences between Indian and Asian-speleothem monsoonal records at the orbital-precession scale.

Citation: Caley, T., Zaragosi, S., Bourget, J., Martinez, P., Malaizé, B., Eynaud, F., Rossignol, L., Garlan, T., and Ellouz-Zimmermann, N.: Southern Hemisphere imprint for Indo–Asian summer monsoons during the last glacial period as revealed by Arabian Sea productivity records, Biogeosciences Discuss., 10, 9315-9343, doi:10.5194/bgd-10-9315-2013, 2013.
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