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.

北半球2300万平方公里的土地--占陆地总面积的四分之一--是永久冻土。这种永久冻结的地面储存的碳是大气中的两倍，其中很大一部分是甲烷。因此，永久冻土的形成和融化是气候系统中一个重要的正反馈，随着地球变冷而消除温室气体，并在今天地球变暖的时期释放温室气体。永久冻土还对生态系统和生物多样性产生强有力的控制，并支撑着许多高纬度地区的人类基础设施（建筑物和交通线路）。对现代环境中活跃的永久冻土过程进行了大量研究（并仍在继续），但评估永久冻土的长期行为已被证明更加困难。我们还不清楚高纬度大陆地区的温度是如何随着时间的推移对全球气候变化做出反应的，也不清楚不同气候状态下永久冻土的范围。这些信息对于今天永久冻土地区的未来规划以及我们对高纬度碳和气候系统的一般理解都很重要。北方的主要冻土区如何对全球气候变化作出反应，如轨道变化或上新世-更新世期间地球的逐渐变冷？永久冻土层在通过其对气候的碳反馈放大这些变化中扮演了什么角色？在这里，我们建议使用形成于洞穴中的碳酸盐（洞穴沉积物）来评估世界上最大的永久冻土区-西伯利亚的永久冻土范围。洞穴沉积物需要水来形成，所以当地面终年结冰时，不会生长。因此，洞穴堆积物的存在或不存在限制了多年冻土的范围。我们一直在研究一系列三个洞穴，这些洞穴从北纬52度伊尔库茨克附近的无冻土区的现代边缘向北延伸，穿过斑块状的永久冻土层，一直延伸到北纬60度的连续永久冻土层边缘。这项工作取得了详细的重建的永久冻土的历史，在过去的450万年，显示融化的永久冻土在每个温暖的间冰期在南部。在北部（60 oN），除了在390-430 ka前的间冰期，当全球条件比现在温暖时，永久冻土保持稳定。我们建议在这些洞穴中继续重建超过~500 ka U-Th测年法极限的多年冻土历史，并在64 oN连续多年冻土区中心增加第四个洞穴。使用新证明的U-Pb测年能力，我们将在上新世-更新世期间测定洞穴沉积物生长的时期，以评估上新世温暖后地球冷却的时间，即西伯利亚永久冻土条件。我们将限制更新世气候变化期间永久冻土的变化范围。通过将这些记录与其他地方的气候信息进行比较，我们将了解高纬度北方大陆对全球气候变化的反应，特别是在比今天更温暖的时期。为了了解每个地点的洞穴温度与洞穴上方年平均温度的关系，我们需要在研究洞穴中进行监测。我们将与俄罗斯科学院的俄罗斯同事和西伯利亚洞穴探险界密切合作开展这项工作。我们还将利用我们在俄罗斯的关系，确保将我们了解到的新信息提供给未来将受到永久冻土变化影响的地区的利益相关者。

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

1,100,000 year history of Siberian permafrost based on U-Pb chronology of speleothems

基于洞穴 U-Pb 年代学的西伯利亚永久冻土 1,100,000 年历史

• 发表时间: 2014
• 作者: Vaks A.