Glacial – Interglacial Changes in Dust Supply to the Pacific Southern Ocean

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This project is designed to unravel the role of changes in South Pacific dust provenance during past Southern Hemisphere climate variations. It has been hypothesized that the glacial increase in dust supply to the Fe-deficient Southern Ocean fostered enhanced primary productivity resulting in a net drawdown of atmospheric CO2. This important feedback mechanism was suggested to have forced the climate system towards full glacial states relying, however, on the assumption that glacial-interglacial changes in the Southern Hemisphere dust cycle occurred zonally largely synchronized. Preliminary work suggests that Australian sources contributed substantially to the dust deposition in the South Pacific, both during the late Holocene and the Last Glacial Maximum (LGM). However, the dust deposition across the LGM South Pacific was characterized by substantial contributions from central South American sources dominating in the Subantarctic Zone whereas their influence in the Antarctic Zone was considerably reduced. Such heterogeneity in dust provenance across the South Pacific implies the possibility that dust mobilization was offset in the respective source areas, which could have influenced the efficiency of biological drawdown of atmospheric CO2 in the glacial Southern Ocean.In order to identify past temporal variations in dust provenance, this project follows a multi-proxy approach comprising the analysis of rare earth element content, lead, neodymium and strontium isotopes of the dust fraction (<5 micrometer) extracted from South Pacific sediment cores PS75/056-1 and PS75/083-1. These two records from the Subantarctic and Antarctic Zone, respectively, will enable the reconstruction of dust provenance changes within the South Pacific across the past ~260,000 years, and to compare their timing with the evolution in the South Atlantic. The same cores will be used by national and international project partners to diagnose complementary parameters including the quantification of lithogenic and biogenic particle fluxes as well as reconstructions of environmental conditions in the dust source regions. The concerted effort with leading experts in the field will, for the first time, allow to comprehensively assess the link of the Southern Hemisphere dust cycle with Southern Ocean biogeochemistry and their significance for glacial-interglacial climate variations.