Orbital variability and high latitude circulation and climate change during the Pliocene-Pleistocene.

该项目旨在调查过去500万年中北冰洋、北欧海和北大西洋高水域之间的深水和中水团交换，重点关注300万至100万年前的时期。这些密集的水团强烈地影响了大西洋经向翻转环流（AMOC），而AMOC反过来又对全球气候产生了强烈的影响。我们建议通过测量它们的放射性同位素特征来重建这些水团的来源、强度和混合以及它们所携带的沉积物的变化。我们的研究将集中在从数百万年到冰期/间冰期变率的时间尺度上尽可能定量地重建北半球冰期大强化（INHG）和中更新世过渡（MPT）的气候高度相关时期的水团动力学。我们建议对形成南北样带的四个ODP/IODP沉积物岩心的样品进行研究；一个在北大西洋高海拔地区（地点984或607），一个在格陵兰-挪威海（地点907），一个在耶尔马克高原的弗拉姆海峡（地点911），以及北极中部的ACEX核心（IODP Leg 302）。对于每个岩心，我们将从自生金属氧化物相确定深水放射性成因钕（Nd）、铅（Pb）和锶（Sr）同位素组成的古变异性，以及从有孔虫方解石中确定Nd同位素组成。大块沉积物放射性成因同位素组成将提供由水团运输的沉积物源区变化的信息。这些代理数据将使我们能够揭示在第四纪开始时三个盆地之间的水团交换以及这些盆地内部和周围的侵蚀物源的变化。我们的主要目标是提高我们对环流和冰川变化在控制和响应气候方面的作用的理解。与仅在晚第四纪记录中看到的结果相比，这些结果将对更广泛的气候控制机制提供更深入的了解，并将有助于改进过去和未来气候变化的模式。

This project aims to investigate deep- and intermediate-water mass exchange between the Arctic Ocean, the Nordic Seas and the high North Atlantic Ocean of the past 5 million years focusing on the period between 3 and 1 million years ago. These dense water masses have strongly affected Atlantic Meridional Overturning Circulation (AMOC), which, in turn, has had a strong impact on global climate. We propose to reconstruct changes in the sources, strength and mixing of these water masses, and in the sediment they carried, from measurements of their radiogenic isotope signatures. Our investigation will focus on an as quantitative as possible reconstruction of the water mass dynamics on timescales from millions of years to glacial/interglacial variability during the climatically highly relevant periods of the major Intensification of Northern Hemisphere Glaciation (INHG) and the Mid-Pleistocene Transition (MPT). We propose to work on samples from four ODP/IODP sediment cores forming a northsouth transect; one in the high North Altantic (Site 984 or 607), one in the Greenland- Norwegian Sea (Site 907), one in the Fram Strait on the Yermak Plateau (Site 911), and the central Arctic ACEX core (IODP Leg 302). For each core, we will determine the paleo variability of the radiogenic neodymium (Nd), lead (Pb) and strontium (Sr) isotope compositions of deep waters from the authigenic metal oxide phase, as well as Nd isotope compositions from foraminiferal calcite. Bulk sediment radiogenic isotope compositions will provide information on changes in source areas of the sediments transported by the water masses. These proxy data will allow us to unravel changes in both exchange of water masses between the three basins, as well as in erosional provenance in and around these basins during the initiation of Quaternary. Our main goal is to improve our understanding of the role of changes in circulation and glaciation in controlling and responding to climate. The results will offer deeper insight into broader climate control mechanisms as compared to those only seen in Late Quaternary records, and will contribute to the refinement of models of both past and future climatic change.