Descent into the Icehouse

下降到冰库

• 批准号: NE/I005595/1
• 负责人: Gavin Foster
• 金额: $ 66.24万
• 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: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI005595%2F1
• 关键词: Descent; into; Icehouse

For the majority (~80 %) of the last 600 million years or so the planet was considerably warmer and wetter than today, and largely ice free - it was in what is known as a 'greenhouse climate state'. The alternate mode, like today, where ice caps blanket both poles - a so called 'icehouse state', is a relatively rare condition for the climate system to be in. Over the last 600 million years the transitions between the two states tend to be rapid and each had dramatic consequences for life on Earth. The most recent of these fundamental climate transitions began around 50 million years ago and culminated at ~34 million years ago at the Eocene/Oligocene boundary with the rapid growth of the Antarctic Ice Sheet. Due to the nature of the rock record, this most recent transition is the best studied and most well documented of the greenhouse to icehouse switches, but nonetheless the processes responsible are still much debated. The most popular hypothesis is that it was caused by a decline in the atmospheric concentration of CO2 - an important greenhouse gas. Although it has been recently confirmed that the final rapid switch at the Eocene/Oligocene boundary was associated with a dramatic decline in CO2, it has also been suggested that CO2 may not have been the main driver of the overall transition. There are instead a number of potential candidates that fall broadly into two camps - either this climate transition was driven purely by processes internal to the Earth (such as uplift of the Himalaya, ocean circulation, or volcanic outgassing of CO2) or it involved some, or all, aspects of the Earth surface, including biology, that can serve to cause and amplify change in a number of important ways. Due to the burning of fossil fuels, atmospheric CO2 concentrations may reach values typical of the greenhouse world of the Eocene by the end of this century. It is therefore becoming imperative to better understand the role of CO2 in driving these natural cycles of Earths climate, and consequently, the principal aim of this proposal is to determine the main driver of this most recent and dramatic switch in climate state. We will achieve this using a multidisciplinary approach that has aspects of both new data collection and computer modelling. The new data we will generate will involve revised estimates of CO2 concentrations and globally widespread estimates of ocean temperature, environmental parameters that cannot be directly determined for the past. We will study the fossil remains of sea-dwelling microscopic organisms, the foraminifers and coccolithophorids. These organisms are very abundant in the mud on the floor of the oceans, providing an invaluable archive of past ocean climate data, and by looking at the chemical composition of their shells or the organic compounds they biosynthesise we can determine how warm or how acidic the ocean was. And from such parameters, we can also deduce how much CO2 was in their environment. Armed with this improved understanding of how the climate system evolved leading up to the greenhouse-icehouse transition we can better investigate the natural processes that caused the change. Given the complex nature of the climate system this is best done with a variety of sophisticated computer modelling approaches. Crucially, it is only by guiding these computer simulations with the new data we have generated that we can isolate which of the myriad of potential processes was responsible for triggering this fundamental shift in climate and better determine how they impacted the evolution of life.

在过去6亿年左右的大部分时间里（约80%），地球比今天温暖和潮湿得多，基本上没有冰-它处于所谓的“温室气候状态”。像今天这样的交替模式，冰帽覆盖两极-所谓的“冰库状态”，是气候系统相对罕见的条件。在过去的6亿年里，这两种状态之间的转变往往是迅速的，每一种都对地球上的生命产生了巨大的影响。这些基本气候转变中最近的一次开始于大约5000万年前，并在大约3400万年前的始新世/渐新世边界随着南极冰盖的快速增长而达到顶峰。由于岩石记录的性质，这一最新的转变是对温室到冰库转变的最好研究和最好记录，但尽管如此，负责的过程仍然存在很大争议。最流行的假设是，它是由大气中二氧化碳浓度下降引起的-一种重要的温室气体。虽然最近已经证实，始新世/渐新世边界的最终快速转换与二氧化碳的急剧下降有关，但也有人认为，二氧化碳可能不是整个过渡的主要驱动力。相反，有一些潜在的候选者大致分为两个阵营-要么这种气候转变纯粹是由地球内部的过程驱动的（如喜马拉雅山的隆起，海洋环流或火山释放二氧化碳），要么它涉及地球表面的一些或所有方面，包括生物学，可以通过许多重要的方式引起和放大变化。由于化石燃料的燃烧，到本世纪末，大气CO2浓度可能达到始新世温室世界的典型值。因此，必须更好地了解二氧化碳在推动地球气候自然周期中的作用，因此，本提案的主要目的是确定气候状态最近和戏剧性转变的主要驱动因素。我们将使用多学科的方法来实现这一目标，该方法包括新数据收集和计算机建模。我们将生成的新数据将涉及对二氧化碳浓度的修订估计和对全球海洋温度的普遍估计，以及过去无法直接确定的环境参数。我们将研究海洋微生物、有孔虫和颗石藻的化石遗迹。这些生物在海底的泥中非常丰富，为过去的海洋气候数据提供了宝贵的档案，通过观察它们外壳的化学成分或它们生物合成的有机化合物，我们可以确定海洋的温度或酸性。从这些参数中，我们还可以推断出他们环境中的二氧化碳含量。有了对气候系统如何演变导致温室-冰库转变的更好理解，我们可以更好地调查导致变化的自然过程。考虑到气候系统的复杂性，最好采用各种复杂的计算机建模方法。至关重要的是，只有用我们生成的新数据指导这些计算机模拟，我们才能分离出无数潜在过程中的哪一个导致了气候的根本变化，并更好地确定它们如何影响生命的进化。

项目成果

Future climate forcing potentially without precedent in the last 420 million years.

• DOI: 10.1038/ncomms14845
• 发表时间: 2017-04-04
• 期刊: Nature communications
• 影响因子: 16.6
• 作者: Foster GL;Royer DL;Lunt DJ
• 通讯作者: Lunt DJ

A record of Neogene seawater d<sup>11</sup>B reconstructed from paired d<sup>11</sup>B analyses on benthic and planktic foraminifera

新近纪海水d记录

• DOI: 10.5194/cp-2015-177
• 发表时间: 2016
• 作者: Greenop R

Pathways to 1.5 °C and 2 °C warming based on observational and geological constraints

• DOI: 10.1038/s41561-017-0054-8
• 发表时间: 2018-02-01
• 期刊: NATURE GEOSCIENCE
• 影响因子: 18.3
• 作者: Goodwin, Philip;Katavouta, Anna;Williams, Richard G.
• 通讯作者: Williams, Richard G.

The impact of Cenozoic cooling on assemblage diversity in planktonic foraminifera.

• DOI: 10.1098/rstb.2015.0224
• 发表时间: 2016-04-05
• 期刊: Philosophical transactions of the Royal Society of London. Series B, Biological sciences
• 作者: Fenton IS;Pearson PN;Dunkley Jones T;Farnsworth A;Lunt DJ;Markwick P;Purvis A
• 通讯作者: Purvis A

Environmental Predictors of Diversity in Recent Planktonic Foraminifera as Recorded in Marine Sediments.

• DOI: 10.1371/journal.pone.0165522
• 发表时间: 2016
• 期刊: PloS one
• 影响因子: 3.7
• 作者: Fenton IS;Pearson PN;Dunkley Jones T;Purvis A
• 通讯作者: Purvis A