The clay mineral footprint of the West Antarctic Ice Sheet in the Amundsen Sea during the last 6 Ma

过去6Ma阿蒙森海南极西部冰盖的粘土矿物足迹

• 批准号: NE/T010975/1
• 负责人: Claus-Dieter Hillenbrand
• 金额: $ 2.99万
• 依托单位: British Antarctic Survey
• 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%2FT010975%2F1
• 关键词: clay; mineral; footprint; West; Antarctic

Computer-model based predictions of future sea-level rise caused by the melting of polar ice sheets in response to global warming suffer from large uncertainties arising from limited knowledge of ice-sheet stability. Our proposed research directly addresses this problem by investigating the vulnerability of the West Antarctic Ice Sheet (WAIS) and contributes to a more reliable risk estimation of its future rapid melting ("collapse"). The bed of the WAIS is largely grounded below sea level and slopes towards the interior of the Antarctic continent, making it prone to melting under warm climatic conditions. Current rapid ice loss observed in the Amundsen Sea sector of the WAIS, especially of Thwaites Glacier, which is a major conduit of ice flow within the WAIS, may mark the onset of its collapse over the next few centuries, resulting in dramatic sea level rise over the coming decades. A total WAIS collapse would raise global sea level by 3.3-5 metres and cause flooding of low-lying coastal areas worldwide, with devastating environmental, economic and societal consequences.Our project will investigate changes in the size of the WAIS during the last six million years by investigating very fine grains that its glaciers had scraped off the underlying bedrock, before transporting them to the Antarctic coast. Here, the grains were released into the ocean and then transported further offshore before they were finally deposited on the seafloor of the Amundsen Sea. Our main objective is to find evidence, whether, when and under which climatic conditions the WAIS collapsed in the past. Some reconstructions of past global sea levels, computer-model simulations and a few geological data, suggest that the WAIS collapsed repeatedly during the past. However, all these findings are either conflicting, or do not provide the time of the last WAIS collapse, which makes it impossible to identify the climatic factors triggering its collapse. Moreover, new results suggest that the past sea-level highstands alternatively resulted from collapse of the Greenlandic Ice Sheet in combination with partial melting of the East Antarctic Ice Sheet, the much larger 'sibling' of the WAIS.We propose to analyse two unique, several hundred meters long sedimentary sequences, that were cored on the seabed of the Amundsen Sea during the International Ocean Discovery Program (IODP) cruise Exp379 in early 2019. Here, in the deep sea of the Amundsen Sea, ocean currents had accumulated fine-grained sediment particles into a feature several hundred metres high with a shape resembling that of a dune on a beach or in a desert. The main difference between this so-called "sediment drift" and a dune is that ocean bottom currents, rather than wind, transported and deposited the grains, which then built up the drift over millions of years, and the size of these particles is silt and clay rather than sand. We intend to investigate the mineralogical composition of the clay fraction of these drift sediments. Over previous years, we had mapped the clay mineralogical composition of modern seafloor sediments along the WAIS coast, which allowed us to 'fingerprint' the grains delivered to the ocean by the various glaciers, and to recognise that the particles supplied by Thwaites Glacier are characterised by a distinct fingerprint. Initial shipboard-analyses on the two Exp379 cores revealed that this fingerprint is often present in the drift sediments, but sometimes it is absent, indicating that Thwaites Glacier did not erode rocks during the times, when the corresponding sediments were deposited. This can only be explained by the absence of grounded ice in the area of the continent covered by the glacier today. As ice-sheet models suggest that any disappearance of Thwaites Glacier may initiate a total WAIS collapse, our intended study will not only answer the questions, how (in-)stable the WAIS really is, but also, whether Thwaites Glacier is the "Achilles' heel" of the WAIS.

由于对冰盖稳定性的了解有限，对全球变暖引起的极地冰盖融化所造成的未来海平面上升的计算机模型预测存在很大的不确定性。我们提出的研究通过调查南极西部冰盖（WAIS）的脆弱性直接解决了这个问题，并有助于对其未来快速融化（“崩溃”）进行更可靠的风险估计。西澳冰床大部分位于海平面以下，并向南极大陆内部倾斜，因此在温暖的气候条件下容易融化。目前在西南极洲的阿蒙森海部分观察到的快速冰损失，特别是西南极洲内冰流的主要通道Thwaites冰川，可能标志着它在未来几个世纪内崩溃的开始，导致海平面在未来几十年内急剧上升。WAIS的完全崩溃将使全球海平面上升3.3-5米，并导致世界各地低洼沿海地区的洪水泛滥，造成破坏性的环境，经济和社会后果。我们的项目将通过调查其冰川从底层基岩上刮下的非常细的颗粒来调查WAIS在过去600万年中的大小变化，然后将它们运送到南极海岸。在这里，这些颗粒被释放到海洋中，然后被运送到更远的海上，最后沉积在阿蒙森海的海底。我们的主要目标是找到证据，是否，何时以及在何种气候条件下WAIS崩溃在过去。一些对过去全球海平面的重建，计算机模型模拟和一些地质数据表明，WAIS在过去多次崩溃。然而，所有这些发现要么相互矛盾，要么没有提供最后一次WAIS崩溃的时间，这使得无法确定触发其崩溃的气候因素。此外，新的研究结果表明，过去的海平面高水位交替导致格陵兰冰盖的崩溃与东南极冰盖的部分融化相结合，东南极冰盖是WAIS的更大的“兄弟”。我们建议分析两个独特的，几百米长的沉积序列，在2019年初的国际海洋发现计划（IODP）Exp 379巡航期间，在阿蒙森海的海底取芯。在阿蒙森海的深海中，洋流将细粒沉积物颗粒堆积成几百米高的地貌，其形状类似于海滩或沙漠中的沙丘。这种所谓的“沉积物漂移”和沙丘之间的主要区别在于，海洋底部的水流，而不是风，运输和沉积了颗粒，然后经过数百万年的堆积，这些颗粒的大小是淤泥和粘土而不是沙子。我们打算调查这些漂移沉积物的粘土部分的矿物组成。在过去的几年里，我们绘制了沿着WAIS海岸的现代海底沉积物的粘土矿物组成图，这使我们能够对各种冰川输送到海洋中的颗粒进行“指纹”，并认识到Thwaites冰川提供的颗粒具有独特的指纹特征。对两个Exp 379岩心的初步船上分析显示，这种指纹通常存在于漂流沉积物中，但有时不存在，这表明斯韦茨冰川在相应的沉积物沉积期间没有侵蚀岩石。这只能解释为在今天冰川覆盖的大陆地区没有地面冰。由于冰盖模型表明，任何消失的思韦茨冰川可能会引发一个总的WAIS崩溃，我们打算的研究将不仅回答的问题，如何（在）稳定的WAIS真的是，而且，是否思韦茨冰川是“阿喀琉斯之踵”的WAIS。

项目成果

Evaluation of geomagnetic relative palaeointensity as a chronostratigraphic tool in the Southern Ocean: Refined Plio-/Pleistocene chronology of IODP Site U1533 (Amundsen Sea, West Antarctica)

• DOI: 10.1016/j.quascirev.2023.108460
• 发表时间: 2024-02
• 期刊: Quaternary Science Reviews
• 影响因子: 4
• 作者: Becky Hopkins;Chuang Xuan;C. Hillenbrand;T. V. van Peer;Yuxi Jin;T. Frederichs;Liang Gao;S. Bohaty

West Antarctic Ice Sheet Dynamics in the Amundsen Sea Sector since the Late Miocene?Tying IODP Expedition 379 Results to Seismic Data

晚中新世以来阿蒙森海区西南极冰盖动态？将 IODP 探险 379 结果与地震数据联系起来

• DOI: 10.3389/feart.2022.976703
• 发表时间: 2022
• 期刊: Frontiers in Earth Science
• 影响因子: 2.9
• 作者: Gille-Petzoldt Johanna;Gohl Karsten;Uenzelmann-Neben Gabriele;Gr?tzner Jens;Klages Johann P.;IODP Expedition 379 Scientists
• 通讯作者: IODP Expedition 379 Scientists

Expedition 379 Preliminary Report: Amundsen Sea West Antarctic Ice Sheet History

379号探险队初步报告：阿蒙森西南极冰盖历史

• DOI: 10.14379/iodp.pr.379.2019
• 发表时间: 2019
• 作者: Gohl K

Evidence for a Highly Dynamic West Antarctic Ice Sheet During the Pliocene

上新世期间南极西部冰盖高度动态的证据

• DOI: 10.1029/2021gl093103
• 发表时间: 2021
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Gohl K