Seminar

The Arctic Ocean plays a key role in Earth’s climate. Deciphering the presence of marine-based ice sheet, the development and disintegration of ice shelves, and changes in sea ice cover and ocean-circulation regimes are crucial steps in understanding climate change in Arctic regions. Since all the ice conditions strongly influence the particle fluxes to the seafloor, it will be possible to use particle flux proxies to obtain knowledge on Arctic Ocean glacial history. 230Th (half-life(t1/2) = 75,690 years) and 231Pa (half-life(t1/2) = 32,760 years) are particle-reactive radionuclides produced uniformly in the ocean by alpha decay of soluble 235U and 234U, respectively, at a constant initial 231Pa/230Th activity ratio of 0.093. After production, both 230Th and 231Pa are adsorbed on settling particles and removed to the underlying sediments. However, the differential oceanic residence times of 231Pa and 230Th strongly impact the sedimentary 231Pa/230Th deposition ratio on a basin-wide scale. This study aims to reconstruct the particle fluxes with the 231Pa/230Th ratio over the last 400,000 years, especially the last four glacial periods (MIS2, MIS4, MIS6 and MIS8) and its implication for the presence of sea ice cover, paleocrystic ice and/or ice shelf at the studied locations. By coupling 230Th and 231Pa isotope geochemistry with traditional sedimentology tools, it should be possible to contribute to the understanding of the mechanisms behind the Arctic oceanographic and climatic changes.