Solving the Oligocene icehouse conundrum

解决渐新世冰室难题

基本信息

批准号：
NE/V018361/1
负责人：
Bridget Wade
金额：
$ 176.6万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2022
资助国家：
英国
起止时间：
2022 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FV018361%2F1
关键词：
Solving Oligocene icehouse conundrum

项目摘要

Today there is a major ice sheet on Antarctica, but this was not always the case. The Antarctic ice sheet formed around 34 million years ago, ushering in the dawn of the "icehouse world". Over the next 11 million years, the climate swung between cooler and warmer states, with sea level falling and rising as ice sheets grew and collapsed. To simulate changes in sea level and climate of this size, computer models require massive fluctuations in CO2. However, we have no evidence of CO2 change of this magnitude, and little idea of how such changes could be accomplished. Furthermore, the existing CO2 reconstructions from this time interval present another major puzzle, as they show a long-term decrease, which appears to be decoupled from long-term climate. These mysterious interactions between CO2, climate, and ice sheets are the "Oligocene icehouse conundrum" that this project aims to solve.Past changes in climate can be reconstructed using chemical fingerprints in fossil shells of foraminifera - sand-sized organisms that live throughout the ocean - the chemistry of these organisms records the environmental conditions at the time they grew, allowing us to reconstruct how environments have changed in the past. The main reason the climate of the Oligocene (~34-23 million years ago) remains such a mystery is because of a previous lack of sedimentary material containing well-preserved foraminifera from this time interval. Previously acquired records are sparse or biased by poor preservation, leaving us with a limited and confused understanding of how the Oligocene climate system operates. Now, for the first time, we have identified sites with abundant and well-preserved foraminifera, thus overcoming a major obstacle in Oligocene climate reconstruction. We will analyse foraminifera to reconstruct critical aspects of the Oligocene climate, such as the temperature, global ice volume, sea level, ocean acidity (pH), atmospheric carbon dioxide and the strength of the biological pump. These kinds of analyses are increasingly used to help determine both how climate has changed in the past and how it might change in the future, including "climate sensitivity", the amount of warming expected due to rising CO2. We have built a team and strategy that poises the project for success. Principal Investigator (PI) Wade is one of the world's foremost experts on the foraminifera of the Oligocene, and so is perfectly placed to figure out which species best record temperatures and atmospheric CO2. Having identified the best species and sites, we will make the first reconstructions of CO2 from this time using the chemistry of boron. This exciting method has seen extensive development in recent years by Co-PI Rae and Co-Investigator Foster, and we will apply the latest methods to determine past pH and CO2. To explore why CO2 may have changed, we will create new records of the biological pump of carbon to the deep ocean. And to evaluate the impact of CO2 on global climate, we will make new records of temperature, using foraminifera and organic molecules, and sea level, using foraminifera from the sea floor. Armed with these new reconstructions of key components of Oligocene climate, we will use a variety of modelling approaches to integrate and interpret them in a global context. A model of how carbon cycles between different reservoirs will allow us to test mechanisms of CO2 change. Simulations of physical climate and ice sheets will be combined in an exciting new way to explore the stability of major ice sheets. We will transform the understanding of CO2 and climate change in the Oligocene, providing insights into the fundamentals of climate sensitivity and ice sheet stability.The new understanding of Oligocene climate and the carbon cycle that will result from our research will resolve the long-standing Oligocene icehouse conundrum, and improve understanding of climate and ice sheet sensitivity in a warmer world.

今天，南极洲有一个大冰盖，但情况并非总是如此。南极冰盖形成于约3400万年前，迎来了“冰库世界”的黎明。在接下来的 1100 万年里，气候在较凉爽和较温暖的状态之间摇摆，随着冰盖的扩张和崩塌，海平面不断下降和上升。为了模拟如此规模的海平面和气候变化，计算机模型需要二氧化碳的巨大波动。然而，我们没有证据表明二氧化碳发生了如此大的变化，也不知道如何实现这种变化。此外，该时间间隔的现有二氧化碳重建提出了另一个主要难题，因为它们显示出长期减少，这似乎与长期气候脱钩。二氧化碳、气候和冰盖之间这些神秘的相互作用是该项目旨在解决的“渐新世冰室难题”。过去的气候变化可以利用有孔虫（生活在整个海洋中的沙子大小的生物）化石壳中的化学指纹来重建- 这些生物体的化学成分记录了它们生长时的环境条件，使我们能够重建过去环境的变化情况。渐新世（约 34-2300 万年前）的气候仍然是一个谜，主要原因是之前缺乏含有该时期保存完好的有孔虫的沉积物质。以前获得的记录很少，或者由于保存不善而有偏差，使我们对渐新世气候系统如何运作的了解有限且混乱。现在，我们首次确定了有孔虫丰富且保存完好的地点，从而克服了渐新世气候重建的重大障碍。我们将分析有孔虫，以重建渐新世气候的关键方面，例如温度、全球冰量、海平面、海洋酸度 (pH)、大气二氧化碳和生物泵的强度。此类分析越来越多地用于帮助确定气候在过去如何变化以及未来可能如何变化，包括“气候敏感性”，即二氧化碳上升导致的变暖程度。我们已经建立了一支团队和战略，为项目的成功做好准备。首席研究员 (PI) 韦德 (Wade) 是世界上渐新世有孔虫领域最重要的专家之一，因此完全有能力找出哪个物种记录的温度和大气二氧化碳含量最好。确定了最佳物种和地点后，我们将利用硼的化学性质首次重建二氧化碳。近年来，Co-PI Rae 和 Co-Investigator Foster 对这种令人兴奋的方法进行了广泛的发展，我们将应用最新的方法来确定过去的 pH 和 CO2。为了探索二氧化碳可能发生变化的原因，我们将创造向深海生物泵碳的新记录。为了评估二氧化碳对全球气候的影响，我们将利用有孔虫和有机分子记录温度，并利用海底有孔虫记录海平面。有了这些对渐新世气候关键组成部分的新重建，我们将使用各种建模方法在全球背景下整合和解释它们。不同储层之间碳循环的模型将使我们能够测试二氧化碳变化的机制。物理气候和冰盖的模拟将以一种令人兴奋的新方式结合起来，以探索主要冰盖的稳定性。我们将转变对渐新世二氧化碳和气候变化的认识，深入了解气候敏感性和冰盖稳定性的基本原理。我们的研究对渐新世气候和碳循环的新认识将解决长期存在的渐新世问题冰室难题，并提高对温暖世界中气候和冰盖敏感性的了解。