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

该项目的目的是调查过去500万年来北冰洋、北欧海和北大西洋高地之间的深水和中层水物质交换，重点是300万至100万年前。这些密集的水团强烈地影响了大西洋经向翻转环流（AMOC），反过来又对全球气候产生了强烈的影响。我们建议重建这些水团的来源，强度和混合的变化，并在他们携带的沉积物，从测量其放射性同位素签名。我们的调查将集中在一个尽可能定量重建的水团动力学的时间尺度从数百万年的冰川/间冰期的变化在气候高度相关的时期的主要的北方半球冰川（INHG）和中更新世过渡（MPT）。我们建议对形成南北样带的四个ODP/IODP沉积物芯样进行研究;一个在北大西洋高地（984或607号站点），一个在格陵兰-挪威海（907号站点），一个在耶尔马克高原的弗拉姆海峡（911号站点），以及北极中部ACEX芯样（IODP 302号航段）。对于每个核心，我们将确定的放射性钕（Nd），铅（Pb）和锶（Sr）同位素组成的深沃茨自生金属氧化物相，以及有孔虫方解石的Nd同位素组成的古变异。散装沉积物的放射性同位素组成将提供信息的来源地区的变化的水团运输的沉积物。这些代理数据将使我们能够解开的变化，在这两个交换的水团之间的三个盆地，以及在这些盆地及其周围的侵蚀源区在第四纪开始。我们的主要目标是提高我们对循环和冰川作用变化在控制和应对气候方面的作用的理解。与仅在晚第四纪记录中看到的机制相比，这些结果将为更广泛的气候控制机制提供更深入的见解，并将有助于改进过去和未来气候变化的模型。

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.