The role of South Pacific dust provenance changes in Pliocene-Pleistocene climate variability (IODP Expedition 383)

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Mineral dust is an important component of the Earth’s climate system. It has been hypothesized that the increase in airborne iron (Fe) supply to the Fe-deficient Southern Ocean promoted 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 during the Late Pleistocene. Similarly, the Southern Ocean dust-Fe feedback has been considered to explain the cooling trends of mid-Pleistocene glacial intervals and during the late Pliocene onset of the Northern Hemisphere Glaciation. Recent work from the South Pacific showed that the Southern Ocean dust-Fe feedback is critically linked with dust emissions from specific Southern Hemisphere source regions and their transport with the predominant westerly winds. In particular, the circumpolar transport of dust from Central South American sources plays a dominant role for the dust deposition in the Subantarctic Zone (SAZ) of the South Pacific. Australian and New Zealand dust input is overall secondary, but their contributions increase during the later stages of glacial cycles. This project is designed to build upon these recent findings and investigate the role of changes in South Pacific dust provenance in the climate variability of the last 5 Ma using marine sediments from IODP Expedition 383 sites U1540 and U1541. The dust fractions will be extracted from the samples and analyzed for their geochemical fingerprint (rare earth elements, and lead, neodymium, and strontium isotopes). Source apportionment with Bayesian mixing models will quantify the contributions from the different potential source areas in every individual sample. These data will be used to identify transport routes and mechanisms of dust delivered to the study area during the last 5 Ma. The same sediment cores are used by national and international project partners to analyze complementary parameters including particle flux and dust grain size measurements. The combination of these datasets will provide, for the first time, a comprehensive picture Southern Hemisphere dust cycle changes and their role in Pliocene-Pleistocene climate variations.