Terrestrial methane cycling during Paleogene greenhouse climates

古近纪温室气候下的陆地甲烷循环

基本信息

批准号：
NE/J008656/1
负责人：
Margaret Collinson
金额：
$ 16.48万
依托单位：
Royal Holloway University of London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ008656%2F1
关键词：
Terrestrial methane cycling during Paleogene

项目摘要

Human activity has led to an increase in pCO2 and methane levels from pre-industrial times to today. While the former increase is primarily due to fossil fuel burning, the increase in methane concentrations is more complex, reflecting not only direct human activity but also feedback mechanisms in the climate system related to temperature and hydrology-induced changes in methane emissions. To unravel these complex relationships, scientists are increasingly interrogating ancient climate systems. Similarly, one of the major challenges in palaeoclimate research is understanding the role of methane biogeochemistry in governing the climate of ice-free, high-pCO2 greenhouse worlds, such as during the early Paleogene (around 50Ma). The lack of proxies for methane concentrations is problematic, as methane emissions from wetlands are governed by precipitation and temperature, such that they could act as important positive or negative feedbacks on climate. In fact, the only estimates for past methane levels (pCH4) arise from our climate-biogeochemistry simulations wherein GCMs have driven the Sheffield dynamic vegetation model, from which methane fluxes have been derived. These suggest that Paleogene pCH4 could have been almost 6x modern pre-industrial levels, and such values would have had a radiative forcing effect nearly equivalent to a doubling of pCO2, an impact that could have been particularly dramatic during time intervals when CO2 levels were already much higher than today's. Thus, an improved understanding of Paleogene pCH4 is crucial to understanding both how biogeochemical processes operate on a warmer Earth and understanding the climate of this important interval in Earth history.We propose to improve, expand and interrogate those model results using improved soil biogeochemistry algorithms, conducting model sensitivity experiments and comparing our results to proxy records for methane cycling in ancient wetlands. The former will provide a better, process-orientated understanding of biogenic trace gas emissions, particularly the emissions of CH4, NOx and N2O. The sensitivity experiments will focus on varying pCO2 levels and manipulation of atmospheric parameters that dictate cloud formation; together, these experiments will constrain the uncertainty in our trace greenhouse gas estimates. To qualitatively test these models, we will quantify lipid biomarkers and determine their carbon isotopic compositions to estimate the size of past methanogenic and methanotrophic populations, and compare them to modern mires and Holocene peat. The final component of our project will be the determination of how these elevated methane (and other trace gas) concentrations served as a positive feedback on global warming.In combination our work will test the hypothesis that elevated pCO2, continental temperatures and precipitation during the Eocene greenhouse caused increased wetland GHG emissions and atmospheric concentrations with a significant feedback on climate, missing from most modelling studies to date. This work is crucial to our understanding of greenhouse climates but such an integrated approach is not being conducted anywhere else in the world; here, it is being led by international experts in organic geochemistry, climate, vegetation and atmospheric modelling, and palaeobotany and coal petrology. It will represent a major step forward in our understanding of ancient biogeochemical cycles as well as their potential response to future global warming.

从工业前时代到今天，人类活动已导致PCO2和甲烷水平的增加。虽然前者的增加主要是由于化石燃料燃烧，但甲烷浓度的增加更为复杂，不仅反映了人类活动的直接活动，还反映了与温度和水文学诱导的甲烷排放变化有关的气候系统中的反馈机制。为了揭示这些复杂的关系，科学家越来越多地询问古代气候系统。同样，古气候研究的主要挑战之一是了解甲烷生物地球化学在管理无冰，高PCO2温室世界的气候中的作用，例如在古代早期（大约50mA）期间。缺乏甲烷浓度的代理是有问题的，因为湿地的甲烷排放受降水和温度的控制，因此它们可以作为气候对气候的重要正面或负面反馈。实际上，对过去甲烷水平（PCH4）的唯一估计是由我们的气候生物地球化学模拟产生的，其中GCM驱动了Sheffield动态植被模型，从而从中得出了甲烷通量。这些表明，古代PCH4本来可以是几乎6倍的现代工业前水平，并且这种值将具有辐射性强迫效应几乎等同于PCO2的增加，这一影响可能在时间间隔尤其引人注目，而二氧化碳水平已经比今天高得多。 Thus, an improved understanding of Paleogene pCH4 is crucial to understanding both how biogeochemical processes operate on a warmer Earth and understanding the climate of this important interval in Earth history.We propose to improve, expand and interrogate those model results using improved soil biogeochemistry algorithms, conducting model sensitivity experiments and comparing our results to proxy records for methane cycling in ancient wetlands.前者将提供对生物痕量气体排放的更好，面向过程的理解，尤其是CH4，NOX和N2O的排放。灵敏度实验将集中于不同的PCO2水平以及对决定云形成的大气参数的操纵。这些实验将共同限制我们的痕量温室气体估计中的不确定性。为了定性测试这些模型，我们将量化脂质生物标志物，并确定其碳同位素组合物，以估计过去的甲烷植物和甲烷营养群体的大小，并将其与现代米尔斯和全新世泥炭进行比较。我们项目的最终组成部分是确定这些甲烷（和其他微量气体）浓度如何作为全球变暖的积极反馈。结合使用，我们的工作将检验以下假设：PCO2升高，始世温室期间的大陆温度和降水量导致湿地GHG的浓度和大气浓度增加，对大多数模型的湿地含量不足，湿地GHG的浓度和大气中的大量反馈是造成的。这项工作对于我们对温室气候的理解至关重要，但是这种综合方法并未在世界其他任何地方进行。在这里，它是由国际有机地球化学，气候，植被和大气建模以及古植物和煤炭学专家领导的。这将代表我们对古代生物地球化学周期的理解以及它们对未来全球变暖的潜在反应的重要一步。

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）

High temperatures in the terrestrial mid-latitudes during the early Palaeogene

DOI：
10.1038/s41561-018-0199-0
发表时间：
2018-07
期刊：
Nature Geoscience
影响因子：
18.3
作者：
B. Naafs;M. Rohrssen;G. Inglis;O. Lähteenoja;S. Feakins;M. Collinson;E. M. Kennedy;P. Singh;M. Singh;D. Lunt;R. Pancost
通讯作者：
B. Naafs;M. Rohrssen;G. Inglis;O. Lähteenoja;S. Feakins;M. Collinson;E. M. Kennedy;P. Singh;M. Singh;D. Lunt;R. Pancost

Terrestrial methane cycle perturbations during the onset of the Paleocene-Eocene Thermal Maximum