Isotopic tracers and chronometers of earth system processes

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The present proposal aims at contributing to research fields pertaining to major Earth system science issues: the dynamics of climate, sea-level changes and biogeochemical cycles, all having impact on society's security and welfare. Stable, radioactive and radiogenic isotopes constitute primary tools for the planned studies. They provide access to geological time and to a large array of physical parameters of the Earth system, thus to pre-instrumental and "pre antropogenically-modified" states of this system, hence to the deciphering of natural mechanisms driving the evolution of the Earth, at time scale varying from million years ago, to the present.In support of climate change modeling, the research seeks to unravel why and how some boundary conditions may drastically modify the climate/ocean system. Instabilities in the Arctic/North Atlantic oceanic circulation represent a critical example. In this context, efforts are made to document the properties of this circulation during warm episodes of the recent geological past of the Earth, when ice-free conditions prevailed, at least seasonally, in the Arctic, and when continental ice was significantly reduced over Greenland and Arctic Canada. In parallel, it is intended to examine external vs. internal processes of the Earth that could explain why and how the natural control of climate shows departure from Milankovitch's theory at sub-millennial time scales, or how they can influence long-term sea-level changes in the amphi-Atlantic. Investigations on isotope cycling and radiometric dating will also be critical i) to monitoring the evolution/response of river systems in eastern Canada to natural vs. anthropogenic climate forcings, ii) to documenting radionuclide mobility at the hydrosphere/lithosphere interface, with application to soil erosion, or nuclear waste storage problems.These research projects are linked to national and international research programs, such as the Canadian Polar Climate Stability Network (PCS-N), the Integrated Ocean Drilling Program (IODP), and the Large River Basin program of the International Atomic Agency of Vienna (IAEA).