Reliable dating of the postglacial ice retreat in West Antarctica by an integrated palaeomagnetic and radiocarbon approach

通过综合古地磁和放射性碳方法对南极洲西部冰期后的冰退缩进行可靠的测年

• 批准号: NE/F000359/1
• 负责人: Claus-Dieter Hillenbrand
• 金额: $ 7.77万
• 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: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF000359%2F1
• 关键词: Reliable; dating; postglacial; ice; retreat

Major environmental change associated with current global warming represents one of the biggest challenges for mankind during the 21st century. For example, ice-sheet melting in West Antarctica contributes ~11% to the present global sea-level rise of ~1.8 mm per year. A complete melting of the West Antarctic Ice Sheet (WAIS), which is likely to take several hundreds or thousands of years, would raise global sea level by ~5 m. This project aims to study the part of the WAIS that is currently showing the most dramatic indications for ice-sheet melting: the Amundsen Sea sector. Global sea level would rise by additional ~1.4 m, if the ice located in the Amundsen Sea sector would melt completely, which is possible to occur within the next two centuries. This melting would cause devastating flooding in many low-lying cities (e.g. New Orleans, London), agricultural areas (e.g. Netherlands, Bangladesh) and atolls (e.g. Maldives), with immense social, economic and ecological consequences. Until now, however, it is unclear if the melting of the WAIS has been occurring for some time and might continue long into the future, or if it is a relatively short-lived phenomenon. It is also unclear if the present WAIS melting is the result of climate warming, which has been ongoing since the end of the last ice age (~12,000 years ago), or of the mainly man-made greenhouse effect, which has influenced global climate for the last 150 years. Therefore, it is essential to study the history of the WAIS since the last ice age, which is the main scientific objective of the proposed project. In the proposed project the history of WAIS will be reconstructed by studying the sediments that make up the sea floor on the continental shelf that surrounds West Antarctica. These sediments are collected by coring several metres down into the seabed. Work that has already been done on the cores selected for this project shows that the WAIS extended far onto the shelf during the last ice age and retreated since then. The project will attempt to determine the timescale and speed of this retreat by the reliable dating of sediments in several cores. The timing of the ice retreat from a particular core site can be determined by radiocarbon dating of the organic remains of planktonic micro-organisms in the sediments. These organisms lived in the ocean waters that flooded onto the shelf as soon as the ice retreated. When the organisms died, their remains were deposited on the seafloor. Thus, their age reveals when the sediment was formed. Scientists have previously tried to date WAIS retreat from the shelf, but many of their dates are uncertain. This is because the marine sediments contain not only the remains from organisms alive shortly before sediment formation, but also much older, fossil organic remains. These remains were eroded from old sedimentary rocks in the Antarctic hinterland by the ice sheet. Glaciers transported the fossil remains and other detritus to the coast and released them into the sea, where they were deposited together with the remains of those planktonic organisms, which just have died. The fossil organic remains increase the apparent radiocarbon age of a sediment sample. The project will use an improved radiocarbon dating technique, which will overcome this problem and provide more accurate radiocarbon ages. Additionally, the project will apply another (independent) technique for dating the sediments. The intensity of the earth's magnetic field changed in a well-known pattern throughout the last 12,000 years. The project will use sophisticated methods for determining the relative variations of the magnetic intensity of the sediments: these reflect the global magnetic intensity variations. The relative magnetic intensity variations of the sediment cores can then be used to determine their age, and thus the time of ice retreat. The results of the proposed project will aid to a much more accurate prediction of future sea-level rise.

与当前全球变暖相关的重大环境变化是21世纪人类面临的最大挑战之一。例如，西南极的冰盖融化对目前全球海平面每年上升约1.8毫米的贡献约为11%。西南极冰盖(WAIS)的完全融化可能需要数百年或数千年的时间，将使全球海平面上升约5米。该项目旨在研究WAIS目前显示出最引人注目的冰盖融化迹象的部分：阿蒙森海部分。如果阿蒙森海地区的冰完全融化，全球海平面将额外上升约1.4米，这有可能在接下来的两个世纪内发生。这种融化将在许多低洼城市(如新奥尔良、伦敦)、农业区(如荷兰、孟加拉国)和环礁(如马尔代夫)造成毁灭性洪灾，造成巨大的社会、经济和生态后果。然而，到目前为止，尚不清楚WAIS的融化是已经发生了一段时间，并可能持续很长一段时间，还是相对短暂的现象。目前还不清楚目前的WAIS融化是气候变暖的结果，气候变暖自上一次冰河时代(约12,000年前)结束以来一直在持续，还是主要是人为温室效应的结果，后者在过去150年里影响了全球气候。因此，有必要研究WAIS自上一个冰河时代以来的历史，这是拟议项目的主要科学目标。在拟议的项目中，将通过研究构成南极洲西部大陆架海底的沉积物来重建WAIS的历史。这些沉积物是通过向下几米深的海床取芯来收集的。已经对为该项目选择的岩心所做的工作表明，在上一个冰河时代，WAIS延伸到大陆架很远，从那时起就撤退了。该项目将试图通过对几个岩芯中的沉积物进行可靠的测年，来确定这种退缩的时间尺度和速度。通过对沉积物中浮游微生物的有机残留物进行放射性碳测年，可以确定冰川从特定核心位置撤退的时间。这些生物生活在冰层一退却就涌上大陆架的海水中。当这些生物死亡时，他们的遗体被存放在海底。因此，它们的年龄揭示了沉积物形成的时间。科学家此前曾试图确定WAIS从货架上撤退的日期，但他们中的许多人都不确定日期。这是因为海洋沉积物不仅含有沉积物形成前不久活着的生物的遗骸，而且还有更古老的有机化石遗骸。这些遗迹是由南极腹地的古老沉积岩被冰盖侵蚀而成的。冰川将化石遗骸和其他碎屑运到海岸，并将它们释放到海洋中，在那里它们与刚刚死亡的浮游生物的遗骸一起存放在那里。化石有机残留物增加了沉积物样品的表观放射性碳年龄。该项目将使用改进的放射性碳测年技术，这将克服这一问题，并提供更准确的放射性碳测年。此外，该项目将应用另一种(独立的)技术来测定沉积物的年代。在过去的12000年里，地球磁场的强度以众所周知的模式发生了变化。该项目将使用复杂的方法来确定沉积物的磁强度的相对变化：这些方法反映了全球磁强度的变化。然后，沉积物核心的相对磁场强度变化可以用来确定它们的年龄，从而确定冰川消退的时间。拟议项目的结果将有助于更准确地预测未来海平面上升。

项目成果

Deglacial history of the West Antarctic Ice Sheet in the western Amundsen Sea Embayment

阿蒙森海湾西部南极洲冰盖的消冰历史

• DOI: 10.1016/j.quascirev.2010.11.020
• 发表时间: 2011
• 期刊: Quaternary Science Reviews
• 影响因子: 4
• 作者: Smith J

The timing of post-LGM ice-sheet retreat in West Antarctica: An integrated palaeomagnetic and radiocarbon approach

西南极洲末次盛冰期后冰盖消退的时间：古地磁和放射性碳综合方法

• 发表时间: 2010
• 期刊: EGU General Assembly Conference Abstracts
• 作者: Hillenbrand Claus-Dieter

Grounding-line retreat of the West Antarctic Ice Sheet from inner Pine Island Bay

• DOI: 10.1130/g33469.1
• 发表时间: 2013-01-01
• 期刊: GEOLOGY
• 影响因子: 5.8
• 作者: Hillenbrand, Claus-Dieter;Kuhn, Gerhard;Vaughan, David G.
• 通讯作者: Vaughan, David G.

New constraints on the timing of West Antarctic Ice Sheet retreat in the eastern Amundsen Sea since the Last Glacial Maximum

自末次盛冰期以来，阿蒙森海东部西南极冰盖退缩时间的新限制

• DOI: 10.1016/j.gloplacha.2014.07.015
• 发表时间: 2014
• 期刊: Global and Planetary Change
• 影响因子: 3.9
• 作者: Smith J

A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum

• DOI: 10.1016/j.quascirev.2014.06.025
• 发表时间: 2014-09-15
• 期刊: QUATERNARY SCIENCE REVIEWS
• 影响因子: 4
• 作者: Bentley, Michael J.;Cofaigh, Colm O.;Zwartz, Dan
• 通讯作者: Zwartz, Dan