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Reconstructing the Pleistocene history of Antarctic Ice Sheet mass loss

重建南极冰盖质量损失的更新世历史

基本信息

批准号：
NE/T006609/1
负责人：
Ian Bailey
金额：
$ 2.83万
依托单位：
UNIVERSITY OF EXETER
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2019
资助国家：
英国
起止时间：
2019 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FT006609%2F1
关键词：
Reconstructing Pleistocene history Antarctic Ice

项目摘要

Today, the polar regions of both hemisphere of our planet are home to large continental ice-sheets, but most scientists think this has not always been the case. When and why did these ice sheets form? Once established, how stable were they, especially during times warmer than today when we might expect them to melt and raise sea level? These are some of the questions we can answer by generating records of past climate change from sediment cores collected from the seafloor. In this study, we are motivated in particular by exploring what the history of the Antarctic Ice Sheet (AIS) preserved marine sediments deposited in the Southern Ocean during the past can tell us about its likely vulnerability to ongoing human-induced global warming. The AIS is composed of ice equivalent to ~58 m of global sea-level and if only a small fraction of this ice was returned to the oceans as water there would be major consequences for hundreds of millions of persons living in low-lying coastal communities around the world. One of the techniques we can use to track past changes in the AIS is to count sand-sized rock fragments and minerals that have been scrapped off the continents by glaciers and delivered to the seafloor by calving and drifting of icebergs, known as ice-rafted debris (IRD). Layers in the marine record from the Southern Ocean packed full of IRD indicate times in the past when the AIS experienced significant ice-mass loss. We can analyse the geochemistry of that IRD and its sedimentology to work out which parts of Antarctica the icebergs responsible for their deposition came from. Identifying the sources of IRD in Antarctic sediments can therefore help us to understand which sectors of the AIS have been responsible for sea-level rise in the geological past.Past intervals of interest include: (1) times when sea level rose rapidly due to global warming and changes in continental ice-volume, as it has done so every ~100,000 years by over ~100 m during late Pleistocene deglaciations of the past half a million years and, (2) warmer-than-present interglacial climates characterised by sea level higher than today, which were also a regular feature of Earth's climate throughout the ~2.6 million year history of the Pleistocene.The Atlantic sector of the Southern Ocean is known as Iceberg Alley because this is where most icebergs shed from Antarctica today melt. Studies of IRD deposited in Iceberg Alley during the most recent deglaciation 10,000 to 22,000 years ago provide robust evidence for rapid variations in AIS deglacial mass-loss and its contribution to sea-level rise at this time. Nothing is known, however, about the sources of this IRD, or about the behaviour of the AIS during older deglacial events of the past half a million years. Fewer studies still have attempted to determine the contribution the AIS might have made to sea-level rise during warmer-than-present Pleistocene interglacials.Our ability to address these unknowns has been hampered in the past by the lack of continuous, high-resolution marine records of AIS history with excellent age control. However, careful application of modern drilling methods to marine sediments in Iceberg Alley this year by the International Ocean Discovery Program during Expedition 382 has helped to remedy this problem. This research will evaluate the potential for Expedition 382 cores to address the above issues by generating the first records of the provenance of IRD deposited in Iceberg Alley during key late Pleistocene deglaciations and an early Pleistocene interglacial, ~1.2 million years ago.

今天，地球两个半球的极地地区都是大型大陆冰盖的所在地，但大多数科学家认为情况并非一直如此。这些冰原是何时以及为什么形成的？一旦形成，它们有多稳定，尤其是在比今天更温暖的时期，我们可能会预计它们会融化并提高海平面？通过从海底收集的沉积物岩心生成过去气候变化的记录，我们可以回答这些问题。在这项研究中，我们的主要动机是探索南极冰盖（AIS）过去沉积在南大洋的海洋沉积物的历史，可以告诉我们它可能容易受到持续的人类引起的全球变暖的影响。AIS由相当于全球海平面约58米的冰组成，如果只有一小部分冰以水的形式回归海洋，将对世界各地生活在低洼沿海社区的数亿人造成严重后果。我们可以用来追踪过去AIS变化的一种技术是，计算被冰川从大陆上刮下来的沙子大小的岩石碎片和矿物质，这些碎片和矿物质通过冰山的崩解和漂流被带到海底，被称为冰筏碎片（IRD）。充满IRD的南大洋海洋记录层表明，过去AIS经历了重大的冰块损失。我们可以分析IRD的地球化学和沉积学，从而找出导致它们沉积的冰山来自南极洲的哪个部分。因此，确定南极沉积物中IRD的来源可以帮助我们了解在过去的地质时期，AIS的哪些部分导致了海平面上升。过去值得关注的时间间隔包括：(1)由于全球变暖和大陆冰量变化而导致海平面迅速上升的时期，因为在过去50万年的更新世晚期冰川消退期间，海平面每10万年上升100多米；(2)比现在更温暖的间冰期气候，其特征是海平面高于今天，这也是更新世约260万年历史中地球气候的常规特征。南大洋的大西洋部分被称为冰山巷，因为今天从南极洲脱落的大多数冰山都在这里融化。对10,000至22,000年前最近一次冰川消融期间沉积在冰山巷的IRD的研究为AIS消融质量损失的快速变化及其对此时海平面上升的贡献提供了强有力的证据。然而，对于这种IRD的来源，以及在过去50万年更早的冰期事件中AIS的行为，我们一无所知。在比现在更温暖的更新世间冰期，仍有较少的研究试图确定AIS可能对海平面上升的贡献。过去，由于缺乏AIS历史的连续、高分辨率海洋记录和良好的年龄控制，我们解决这些未知问题的能力受到了阻碍。然而，今年国际海洋发现项目的382号考察队在冰山巷小心翼翼地使用现代钻探方法对海洋沉积物进行钻探，帮助解决了这个问题。本研究将评估382号科考队岩心在解决上述问题方面的潜力，通过生成第一个记录，记录在关键的晚更新世脱冰期和早更新世间冰期沉积在冰山Alley的IRD物源，约120万年前。