Glacial/interglacial changes in export production in a series of sediment cores spanning the Indian sector Antarctic Polar Front

Tuesday, 16 December 2014
Sam Jaccard1, Lena Thöle1, Alfredo Martinez-Garcia2, Anja Studer3, Elisabeth Michel4 and Alain Mazaud4, (1)University of Bern, Bern, Switzerland, (2)ETH Swiss Federal Institute of Technology Zurich, Zurich, Switzerland, (3)Princeton University, Princeton, NJ, United States, (4)LSCE Laboratoire des Sciences du Climat et de l'Environnement, Gif-Sur-Yvette Cedex, France
Export of organic carbon from surface waters of the Antarctic Zone of the Southern Ocean decreased during the last ice age, coinciding with declining atmospheric carbon dioxide (CO2) concentrations, signaling reduced exchange of CO2 between the ocean interior and the atmosphere. In contrast, in the Subantarctic Zone, export production increased into ice ages coinciding with rising dust fluxes, thus suggesting iron fertilization of Subantarctic phytoplankton. Recently developed XRF core-scanning methods permit paleoceanographic reconstructions on time-scales similar to ice core temperature and atmospheric carbon dioxide measurements. We have investigated the sedimentary distribution of various proxies allowing reconstructing export production in a series of sedimentary archives retrieved from the Indian Sector of the Southern Ocean spanning the Antarctic Polar Front in the vicinity of Kerguelen Island (Marion Dufresne Expeditions IndienSud-1 & 2). These high-resolution measurements are complemented with reconstruction of 230Th-normalized biogenic particle flux to the seafloor covering the last glacial termination.
This contribution will explore the effects of Fe-fertilization on export production in an area remote from major dust sources. Furthermore, quantitative vertical flux determinations will allow comparing carbon export efficiency in the Indian Ocean with previously published records from the South Atlantic.