Reconstruction of Pliocene-Middle Pleistocene evolution of Siberian permafrost using U-Pb dating of speleothems

利用洞穴石U-Pb测年重建西伯利亚多年冻土的上新世-中更新世演化

• 批准号: NE/K005057/1
• 负责人: Anton Vaks
• 金额: $ 37.67万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FK005057%2F1
• 关键词: Reconstruction; Pliocene; Middle; Pleistocene; evolution

Twenty three million square kilometres of northern-hemisphere land - one quarter of the total land area - is permafrost. This permanently frozen ground stores twice as much carbon as the atmosphere contains, with a significant fraction of this carbon as methane. Formation and thawing of permafrost is therefore a significant positive feedback in the climate system, removing greenhouse gas as Earth cools, and releasing it, in periods such as today, when the planet is warming. Permafrost also exerts a strong control on ecosystems and biodiversity, and it underpins human infrastructure (buildings and transport links) in many high-latitude settings.A significant body of research exists (and continues) into active permafrost processes in the modern environment, but assessing the long-term behaviour of permafrost has proved more difficult. We do not yet have a clear idea of how the temperature of high-latitude continental regions responds to changing of global climates through time, nor of the extent of permafrost in different climate states. Such information is important for future planning in today's permafrost regions, and for our general understanding of high-latitude carbon and climate systems. How do the major permafrost regions of the northern hemisphere respond to global climate change such as orbital variation or the progressive cooling of the planet during the Plio-Pleistocene? And what role might permafrost have in these amplifying these changes through its carbon feedbacks on climate? Here we propose to use carbonates formed in caves (speleothems) to assess the extent of permafrost in the world's largest area of permafrost - Siberia. Speleothems require water to form so, when the ground is frozen year-round, do not grow. The presence or absence of speleothems therefore constrains the extent of permafrost through time. We have been working on a sequence of three caves which stretch from the modern edge of the permafrost-free zone near Irkutsk at 52oN, northwards through patchy permafrost and to the edge of continuous permafrost at 60oN. This work has yielded a detailed reconstruction of the permafrost history during the last 450 ka, showing thawing of the permafrost in each warm interglacial period in the south. In the north (60oN) the permafrost remained stable except during the interglacial period 390-430 ka ago when global conditions were warmer than present. We propose to continue the reconstruction of the permafrost history beyond the ~500 ka limit of the U-Th dating method in these caves, and to add a fourth cave in the centre of the continuous permafrost region at 64oN. Using a newly proven U-Pb dating ability, we will date periods of speleothem growth during the Plio-Pleistocne to assess the time, as the planet cooled after the warmth of the Pliocene, that permafrost conditions initiated in Siberia. And we will constrain the changing extent of permafrost during the variable climates of the Pleistocene. By comparing these records with information about climate elsewhere, we will learn how the high latitude northern continents respond to global climate change, particularly during periods warmer than today.To understand how the cave temperatures in each location related to annual mean temperatures above the caves will require a campaign of monitoring in our study caves. We will conduct this work in close collaboration with Russian colleagues from the Russian Academy of Sciences and the well-established Siberian caving community. We will also use our connections in Russia to ensure that new information we learn is provided to stakeholders in regions that will be impacted by changing permafrost in the future.

北山脉北部土地的2300万平方公里 - 占地总面积的四分之一 - 是多年冻土。这种永久冷冻的地面存储的碳含量是大气中包含的两倍，而该碳的大部分是甲烷。因此，多年冻土的形成和解冻是气候系统中的显着积极反馈，随着地球的冷却而去除温室气体，并在如今的时期（如今天的行星变暖时）释放。多年冻土还对生态系统和生物多样性产生了强大的控制，并且它在许多高纬度环境中为人类基础设施（建筑物和运输链路）支撑。我们尚不清楚高纬度大陆区域的温度如何响应随着时间的流逝而变化的全球气候变化，也不是在不同气候状态下的永久冻土程度。此类信息对于当今多年冻土地区的未来计划以及我们对高纬度碳和气候系统的一般理解至关重要。北半球的主要多年冻土区域如何应对全球气候变化，例如轨道变化或Plio-Pleistecene期间地球的进行性冷却？多年冻土在这些变化中通过其气候的反馈来扩大这些变化的作用？在这里，我们建议使用在洞穴中形成的碳酸盐（Speleothems）来评估世界上最大的永久冻土区域 - 西伯利亚的多年冻土程度。 Speleothems需要水才能形成，因此，当地面全年冷冻时，不会生长。因此，斑点的存在或不存在会限制随着时间的流逝的永久冻土程度。我们一直在研究三个洞穴的序列，这些洞穴从52on的Irkutsk附近的永久冻土区的现代边缘延伸，向北，通过斑点的多年冻土，再到60on的连续永久冻土边缘。这项工作已在过去的450 ka期间对永久冻土历史进行了详细的重建，显示了南部每个温暖的冰河冰冻时期的融化。在北部（60年代），除非在390-430 ka前的冰间期间，全球状况比现在更加温暖，但多年冻土仍保持稳定。我们建议在这些洞穴中继续重建多年冻土历史，超过第u级约会方法的约500 ka限制，并在64on连续的多年冻土区域的中心增加第四个洞穴。使用新近证明的U-PB约会能力，我们将在Plio-Pleistocne期间约会speleothem生长的时期，以评估该行星在上新世加热后冷却的时间，即在西伯利亚开始了多年的冻土条件。我们将限制在更新世的可变气候中多年冻土的变化程度。通过将这些记录与其他地方的气候信息进行比较，我们将学习如何对全球气候变化做出反应，尤其是在比今天温暖的时期内，了解与洞穴上方年平均温度相关的每个位置中的洞穴温度如何需要在我们的研究洞穴中进行监测。我们将与俄罗斯科学院和公认的西伯利亚洞穴界的俄罗斯同事密切合作进行这项工作。我们还将利用我们在俄罗斯的联系来确保向我们学习的新信息提供给地区的利益相关者，这些信息将来会因未来的多年冻土而影响。

项目成果

1,350,000 Year History of Siberian Permafrost Based on U-Pb Chronology of Speleothems

基于 U-Pb 洞穴年代学的西伯利亚永久冻土层 1,350,000 年历史

• 发表时间: 2014
• 期刊: AGU Fall Meeting Abstracts
• 作者: Vaks A.

Lithium isotopes in speleothems: Temperature-controlled variation in silicate weathering during glacial cycles

• DOI: 10.1016/j.epsl.2017.04.014
• 发表时间: 2017-07
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: P. V. Strandmann;A. Vaks;M. Bar-Matthews;A. Ayalon;E. Jacob;G. Henderson

An Acetic Acid-Based Extraction Protocol for the Recovery of U, Th and Pb from Calcium Carbonates for U-(Th)-Pb Geochronology

用于从碳酸钙中回收 U、Th 和 Pb 进行 U-(Th)-Pb 地质年代学的乙酸萃取方案

• DOI: 10.1111/j.1751-908x.2013.00219.x
• 发表时间: 2013
• 期刊: Geostandards and Geoanalytical Research
• 影响因子: 3.8
• 作者: Mason A

Palaeoclimate evidence of vulnerable permafrost during times of low sea ice

• DOI: 10.1038/s41586-019-1880-1
• 发表时间: 2020-01
• 期刊: Nature
• 影响因子: 64.8
• 作者: A. Vaks;A. Mason;S. F. M. Breitenbach;Aleksandr Kononov;Alexander V. Osinzev;M. Rosensaft;A. Borshevsky;Oksana Gutareva;Gideon M. Henderson

A simplified isotope dilution approach for the U-Pb dating of speleogenic and other low-<sup>232</sup>Th carbonates by multi-collector ICP-MS

一种简化的同位素稀释方法，用于对洞穴和其他低浓度的 U-Pb 定年

• DOI: 10.5194/gchron-2020-37
• 发表时间: 2021
• 作者: Mason A