What caused the Mid Pleistocene Transition? Insights from a new high resolution CO2 record

是什么导致了中更新世过渡？

基本信息

批准号：
NE/P011381/1
负责人：
Gavin Foster
金额：
$ 63.2万
依托单位：
University of Southampton
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FP011381%2F1
关键词：
What caused Mid Pleistocene Transition

项目摘要

The geological past contains many examples of Earth's climate being different to today and these are excellent test beds for our understanding of the climate system and ultimately our predictions of our future climate. Over the last 600 thousand years (kyr) or so, the Earth's climate has regularly oscillated, roughly every 100 kyr, between warm "interglacial" periods with climates similar to today, and frigid "glacial" periods when several kilometres of ice blanketed North America and northern Europe (at times extending into Siberia). Bubbles of ancient air trapped in ice cores from Antarctica reveal that these cyclical changes in climate were partly driven by changes in the atmospheric concentration of the greenhouse gas carbon dioxide (CO2) - CO2 was low during glacial periods and high during intervening interglacial periods. During each ice age cycle, cooling towards peak glacial climates tended to be rather slow (taking around 90 kyr) whereas the warming that terminates each glacial period tended to be very quick (~10 kyr in length). However, before about 1.2 million years ago Earth's climate was warmer on average, there was less ice on the continents and climate cycles were more regular, symmetric, and shorter - they followed a 41 kyr orbital beat at that time. Gradually between 1.2 and 0.6 million years ago, the character of glacial-interglacial cycles changed, shifting from these smaller 41-kyr cycles to the more recent larger 100-kyr cycles. Climate scientists have studied this important interval, known as the Mid Pleistocene Transition (MPT), for decades to learn about the inner workings of the climate system, but as yet the underlying cause remains debated. Despite their contrasting character, these two types of climate cycle were both paced by subtle variations in the amount and the spatial and seasonal distribution of sunlight reaching the Earth's surface as a result of regular changes in how the Earth orbits the sun (known as orbital cycles). What is puzzling is that the change in the nature of the climate cycles occurred in the absence of any notable change in these orbital cycles. It therefore represents a fundamental change in the way the climate system operates and in particular how certain feedbacks behave when the climate system is subjected to forcing. In order to test which, if any, of the available models adequately explains this transition we need reconstructions of both the size of the continental ice sheets and knowledge of the concentration of atmospheric CO2. While the evolution of ice volume through time is known relatively well, the direct ice core record of atmospheric CO2 only covers the last 800 thousand years and it is unlikely that it can be extended further back in the near future (if at all). We therefore have to use other, more indirect methods to reconstruct the CO2 content of the ancient atmosphere. One approach with a proven track record uses the boron (B) isotopic composition of calcareous microfossils called foraminifera, which steadily accumulate over time in deep-sea sediments. There are two naturally occurring isotopes of boron and the ratio of these two isotopes, 11B to 10B, in the shells of foraminifera reflects the acidity of the ocean surface when they lived, and from this it is possible to estimate atmospheric CO2 at that time. The principal aim of this proposal is to use this method to produce a record of CO2 for the last 1.3 million years that overlaps with the ice core CO2 record but then extends this back to cover the Mid Pleistocene Transition. Putting our current understanding of the MPT to the test in this way promises new insights into the coupling of climate change and the global carbon cycle, thereby also ultimately shedding light on how climate and polar ice sheets will respond to fossil fuel burning.

地质过去包含许多地球气候与今天不同的例子，这些是我们了解气候系统以及最终预测未来气候的极好试验台。在过去 60 万年（kyr）左右的时间里，地球气候有规律地波动，大约每 100 kyr，在气候与今天相似的温暖“间冰期”和寒冷“冰河期”之间波动，当时北美有数公里厚的冰层覆盖和北欧（有时延伸到西伯利亚）。南极洲冰芯中的古代空气气泡表明，这些气候的周期性变化部分是由大气中温室气体二氧化碳（CO2）浓度的变化驱动的——二氧化碳在冰期期间较低，而在间冰期期间较高。在每个冰河期周期中，到达冰川气候高峰期的冷却往往相当缓慢（大约需要 90 kyr），而每个冰川期结束时的变暖往往非常快（长度约为 10 kyr）。然而，在大约 120 万年前，地球气候平均变暖，大陆上的冰较少，气候周期更加规则、对称且较短——当时它们遵循 41 kyr 的轨道节拍。在 1.2 至 60 万年前，冰期-间冰期循环的特征逐渐发生了变化，从这些较小的 41 kyr 循环转变为最近的较大 100 kyr 循环。气候科学家几十年来一直在研究这个被称为中更新世转变（MPT）的重要时期，以了解气候系统的内部运作，但迄今为止其根本原因仍然存在争议。尽管它们的特征截然不同，但这两种类型的气候周期都是由到达地球表面的阳光的数量以及空间和季节分布的微妙变化所决定的，这是由于地球绕太阳运行的方式发生定期变化（称为轨道周期））。令人费解的是，气候周期性质的变化是在这些轨道周期没有任何显着变化的情况下发生的。因此，它代表了气候系统运行方式的根本性变化，特别是当气候系统受到强迫时某些反馈的行为方式。为了测试哪些可用模型（如果有的话）能够充分解释这种转变，我们需要重建大陆冰盖的大小和大气二氧化碳浓度的知识。虽然冰体积随时间的演变相对清楚，但大气二氧化碳的直接冰芯记录仅涵盖过去 80 万年，并且在不久的将来不太可能进一步延伸（如果有的话）。因此，我们必须使用其他更间接的方法来重建古代大气中的二氧化碳含量。一种经过验证的方法使用了被称为有孔虫的钙质微化石的硼 (B) 同位素组成，这种化石随着时间的推移在深海沉积物中稳定积累。有两种天然存在的硼同位素，有孔虫壳中这两种同位素 11B 与 10B 的比率反映了它们生活时海洋表面的酸度，由此可以估算当时大气中的二氧化碳浓度。该提案的主要目的是利用这种方法生成过去 130 万年的二氧化碳记录，该记录与冰芯二氧化碳记录重叠，但随后将其延伸至更新世中期过渡期。以这种方式检验我们目前对 MPT 的理解，有望对气候变化与全球碳循环的耦合产生新的见解，从而最终揭示气候和极地冰盖将如何响应化石燃料燃烧。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Dynamic storage of glacial CO2 in the Atlantic Ocean revealed by boron [CO 3 2 - ] and pH records

硼 [CO 3 2 - ] 和 pH 记录揭示了大西洋冰川 CO2 的动态储存

DOI：
http://dx.10.1016/j.epsl.2018.12.022
发表时间：
2019
期刊：
Earth and Planetary Science Letters
影响因子：
5.3
作者：
Chalk T
通讯作者：
Chalk T

Toward a Cenozoic history of atmospheric CO2.

大气二氧化碳的新生代历史。

DOI：
http://dx.10.1126/science.adi5177
发表时间：
CenCO2PIP
期刊：
Science (New York, N.Y.)
影响因子：
0
作者：
Cenozoic CO2 Proxy Integration Project (CenCO2PIP) Consortium*†
通讯作者：
Cenozoic CO2 Proxy Integration Project (CenCO2PIP) Consortium*†

Author Correction: Atmospheric CO2 during the Mid-Piacenzian Warm Period and the M2 glaciation.

作者更正：中皮亚琴兹暖期和 M2 冰川时期的大气二氧化碳。

DOI：
http://dx.10.1038/s41598-021-93282-w
发表时间：
2021
期刊：
Scientific reports
影响因子：
4.6
作者：
De La Vega E
通讯作者：
De La Vega E

Orbital CO 2 reconstruction using boron isotopes during the late Pleistocene, an assessment of accuracy

使用硼同位素重建晚更新世期间的轨道CO 2 ，评估准确性

DOI：
http://dx.10.5194/cp-2022-93
发表时间：
2023
期刊：
影响因子：
0
作者：
De La Vega E
通讯作者：
De La Vega E

Orbital CO 2 reconstruction using boron isotopes during the late Pleistocene, an assessment of accuracy

使用硼同位素重建晚更新世期间的轨道CO 2 ，评估准确性

DOI：
http://dx.10.5194/cp-19-2493-2023
发表时间：
2023
期刊：
Climate of the Past
影响因子：
4.3
作者：
De La Vega E
通讯作者：
De La Vega E

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Gavin Foster其他文献

The dual diagnosis clinician shared care model – a clinical mental health dual diagnosis integrated treatment initiative

双诊断临床医生共享护理模式——临床心理健康双诊断综合治疗倡议

DOI：
发表时间：
2022
期刊：
Advances in Dual Diagnosis: Policy, practice and research in mental health and substance use
影响因子：
0
作者：
Gavin Foster;John Robertson;Sophia Pallis;J. Segal
通讯作者：
J. Segal