[M-IS14] Global climate change driven by the Southern Ocean and the Antarctic Ice Sheet

[MIS14-P11] Lithogenic fluxes across a transect in the SW Indian Ocean since the last glacial inception

*Eri Helen Amsler¹, Walter Geibert², Gerhard Kuhn², Minoru Ikehara³, Samuel Jaccard¹ (1.Institute of Geological Sciences and Oeschger Centre for Climate Change Research, University of Bern, Switzerland, 2.Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany, 3.Center for Advanced Marine Core Research, Kochi University, Kochi, Japan)

Keywords:Southern Ocean, Biological Pump

On glacial-interglacial time scale the Southern Ocean plays a prominent role in modulating climate by storing and redistributing heat, fresh water, carbon and nutrients globally. Atmospheric CO₂ is taken up by algae and sequestered in the deep ocean through the biological carbon pump. On the other hand, CO₂ is released back to the atmosphere through upwelling and vertical mixing [1]. The relative contribution of these two mechanisms controls the efficiency through which carbon can be sequestered in the ocean interior.

The effect of iron fertilization on biological productivity has previously been documented in the Atlantic and Pacific sectors of the Southern Ocean [2, 3]. During glacial periods higher input of Fe-bearing dust increased phytoplankton growth and carbon sequestration, thus leading to the drawdown of atmospheric CO₂, accounting for about half of the glacial-interglacial CO₂ amplitude [4].

Here we present ²³⁰Th-normalized lithogenic fluxes in a set of marine sediment cores spanning a meridional transect in the Indian sector of the Southern Ocean further away from the Patagonian dust plume and show that increased Fe flux impacted export production patterns, contributing to the sequestration of carbon away from the atmosphere.

[1] Sigman, D. M., Boyle, E. A. (2000) Nature 407, 859-869.

[2] Martínez-Garcia, A., Sigman, D. M., Haojia, R., Anderson, R. F., Straub, M., Hodell, D. A., Jaccard, S. L., Eglinton, T. I., Haug, G. H. (2014) Science 343, 1347-1350.

[3] Lamy F., Gersonde, R., Winckler, G., Esper, O., Jaeschke, A., Kuhn, G., Ullermann, J., Martínez-Garcia, A., Lambert, F., Kilian, R. (2014) Science 343 (6169), 403-407.

[4] Hain, M. P., D. M. Sigman, and G. H. Haug (2010) Global Biogeochem. Cycles, 24, GB4023.
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