PhD - High-resolution investigation of the Antarctic Circumpolar Current over the last 25000 years

Université Lille

Lille, France

Description

The knowledge of the carbon cycle budget is one of the biggest challenge in paleoclimatology, and the relationships between CO2 concentration changes and the modification of deep oceanic circulation over the last climatic cycles are still a matter of debate. Several evidences indicate that most of the changes in CO2 atmosphere-ocean exchanges must have taken place in the southern ocean. At present, the southern ocean acts as a major sink for CO2 of anthropic origin while it appears to have been a source of CO2 during the last deglaciation. It has recently been suggested that modifications of the Antarctic Circumpolar Current pattern (ACC) vigor and position may have been associated with these changes in CO2 exchanges, in particular during the rapid climatic events of the last deglaciation. Some studies around Kerguelen Plateau have actually shown that the characteristics of the ACC during the last glacial period were indeed different compared to the Holocene. The present project proposes to investigate further the modification of the ACC between the last glacial period and the Holocene using the terrigenous fraction of sediments deposited on the Kerguelen Plateau. Fine-grain particles can be advected for thousand of kilometres within deep currents, and changes in particle provenance are thus largely ascribed to modifications of the circulation of deep-water masses. In the proposed project, the mineralogical and geochemical signatures of detrital particles will thus be used in order to (1) track modifications of the terrigenous transfer - provenance and flux- through the ACC and (2) to document deep-current reorganization. A series of cores, collected during the INDIEN-Sud cruise on the Kerguelen Plateau, will be investigated in order to constrain hydrological changes, including the intensity and location of the ACC in the Indian part of the Southern ocean over the last 25000 years. The candidate will focus on characterizing the terrigenous fraction of sediment cores taken off Kerguelen in order to constrain particles provenance, reconstruct the evolution of the ACC over the last climatic cycle, and improve paleoceanographic reconstitutions. A multiproxy approach, including clay mineralogy, grain-size analyses and radiogenic isotopes will be employed. The PhD student working on this project will be trained in a diverse number of state-of-the-art analytical techniques. The PhD student will be responsible for preparing and processing samples for mineralogy, grain- size and radiogenic isotopes analyses.

Requirements

The candidate should have a Masters degree (or equivalent) in paleoclimatology, sedimentology, geochemistry or a related subject. We seek a highly motivated student, interested in paleoclimatology and in analytical chemical labwork. Some experience in clean-lab environments and in isotopic measurements by TIMS or MC- ICP-MS would be an advantage. Good skills in English are requested. The knowledge of French will be a plus, but is not required. The candidate is expected to work independently on the subject and to interact with international researchers with diverse expertise.

More information and applications

Interested candidates should contact Viviane-Bout Roumazeilles and/or Aloys Bory asap (selection will start on May 28) and in any case before 21 June 2013 (viviane.bout@univ-lille1.fr ; aloys.bory@univ-lille1.fr ).