Isotopic tracers and chronometers of earth system processes

本提案旨在促进与主要地球系统科学问题有关的研究领域：气候动力学、海平面变化和生物地球化学循环，所有这些都对社会安全和福利产生影响。稳定的、放射性的和引起放射性的同位素是计划进行的研究的主要工具。它们提供了了解地质年代和地球系统大量物理参数的途径，从而了解该系统的前仪器和“前人类活动修改”状态，从而破译驱动地球进化的自然机制，时间尺度从百万年前到现在不等。为了支持气候变化模型，这项研究试图揭示为什么以及如何一些边界条件可能会极大地改变气候/海洋系统。北极/北大西洋环流的不稳定就是一个重要的例子。在此背景下，研究人员努力记录这种环流在地球最近地质历史温暖时期的特性，当时北极地区至少季节性地处于无冰状态，格陵兰岛和加拿大北极地区的大陆冰显著减少。与此同时，它还打算研究地球的外部和内部过程，这些过程可以解释气候的自然控制为何以及如何在次千年的时间尺度上偏离米兰科维奇的理论，或者它们如何影响大西洋两岸的长期海平面变化。同位素循环和放射性测年的研究也将至关重要：1)监测加拿大东部河流系统对自然与人为气候强迫的演变/响应；2)记录水圈/岩石圈界面的放射性核素流动性，并将其应用于土壤侵蚀或核废料储存问题。这些研究项目与国家和国际研究项目有关，如加拿大极地气候稳定网络（PCS-N）、综合海洋钻探计划（IODP）和维也纳国际原子能机构（IAEA）的大河流域计划。

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).