Climatically controlled sedimentation dynamics and export productivity at IODP Site U1537 in the Scotia Sea (Southern Ocean) over the past four glacial cycles

过去四个冰川周期中斯科舍海（南大洋）IODP 站点 U1537 的气候控制沉积动态和出口生产力

• 批准号: 508144612
• 负责人: Professor Dr. Anton Eisenhauer
• 金额: --
• 依托单位: GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/508144612?language=en
• 关键词: Climatically; controlled; sedimentation; dynamics; export

The Scotia Sea in the Southern Ocean (SO) today is a hydrodynamically important area where Antarctic Bottom Water (AABW) that is previously formed within the Weddell Sea is vigorously mixing into the Antarctic Circumpolar Current. Furthermore, the Scotia Sea is the area where most icebergs that are shedding off marine-based portions of the Antarctic Ice Sheet are drifting out of the Weddell Sea within the so-called “Iceberg Alley”. During past glacial cycles, the position, dimensions and volume transport of the ACC and AABW were substantially different from the modern configuration. This IODP research proposal, aimed to be realised in the framework of a PhD studentship, seeks to identify the continental source areas of sediments deposited at IODP Site 1537 (59°6.65′S, 40°54.37′W, in 3713 m water depth) that was drilled during Expedition 382 during early 2019. Using the detrital neodymium and lead isotope composition of the bulk and fine (<5 µm) grain size fraction, we will identify continental source areas of terrigenous sediments deposited over the past 450 kyr, hence covering four 100-kyr glacial cycles and five glacial terminations at near-millennial resolution. During key intervals these records will be corroborated by additional argon isotopic analyses on the same sediments. Source areas are expected to be mostly positioned within or close to the Weddell Sea and include older cratonic East Antarctic sequences, as well as relatively young continental crust that is supplied as glacially weathered sediment from the Antarctic Peninsula, Pacific sections of West Antarctica, or dust from Patagonia. We will further generate uranium/thorium isotopic data on bulk sediments to assess sedimentation dynamics (focusing versus winnowing) and assess bottom water oxygen starvation as a function of elevated export productivity in the region.Overturning dynamics in the Antarctic zone of the SO were likely much reduced due to a northward shift of the oceanic fronts as well as extended sea ice cover during the past glacial climates. As a consequence, less sediment from more remote locations such as East Antarctica should have been transported to the core site, while regional export productivity was also reduced given extended sea ice and lowered Scotia Sea surface water nutrient concentrations due to reduced glacial upwelling. We hypothesize that sediment provenance, sedimentation dynamics, as well as surface ocean export productivity in the Scotia Sea are strongly linked on millennial timescales. Our aim is to provide a new perspective on the degree of connectivity between, and underlying controls of, the position of SO fronts, the status of Weddell Sea Deep Water export, and bottom water oxygen starvation as a function of elevated surface ocean productivity.

南大洋（SO）的斯科舍海（Scotia Sea）今天是一个重要的水动力区域，南极底层水（AABW）以前在威德尔海（Weddell Sea）内形成，正在积极地混合到南极绕极流中。此外，斯科舍海是大多数冰山从南极冰盖的海洋部分脱落的地区，这些冰山正在所谓的“冰山巷”内漂出威德尔海。在过去的冰期循环中，ACC和AABW的位置，尺寸和体积输运与现代配置有很大的不同。该IODP研究提案旨在在博士生奖学金的框架内实现，旨在确定IODP 1537号站点（59°6.65′S，40°54.37′W，水深3713米）沉积物的大陆源区，该站点在2019年初的382号考察期间钻探。利用大颗粒和细颗粒（<5 µm）的碎屑钕和铅同位素组成，我们将确定过去45万年沉积的陆源沉积物的大陆源区，因此覆盖了近千年分辨率的4个10万年冰川循环和5个冰川终止。在关键的时间间隔内，这些记录将通过对同一沉积物进行额外的氩同位素分析来证实。预计源区主要位于威德尔海内或附近，包括较老的东南极南极层序，以及相对年轻的大陆地壳，这些大陆地壳是南极半岛、西南极洲太平洋部分的冰川风化沉积物或巴塔哥尼亚的尘埃。我们将进一步生成散装沉积物的铀/钍同位素数据，以评估沉积动力学（聚焦与风选）和评估底层水氧饥饿作为一个功能的提高出口productivity在regions.Overturning动力学在南极地区的SO可能大大减少，由于向北移动的海洋锋，以及在过去的冰川气候扩展海冰覆盖。因此，从东南极洲等较偏远地区运至核心地点的沉积物本应减少，而由于海冰扩展和冰川上涌减少导致斯科舍海表层水营养物浓度降低，区域出口生产力也降低。我们假设，沉积物的来源，沉积动力学，以及在斯科舍海的表层海洋出口生产力密切相关的千年时间尺度。我们的目标是提供一个新的视角之间的连接程度，和潜在的控制，SO前线的位置，威德尔海深水出口的状态，和底层水氧饥饿作为一个功能的提高表层海洋生产力。