Investigation of the Southern Methane Anomaly: causes, implications, and relevance to past global events.

甲烷是第二大温室气体，对影响臭氧的大气化学有贡献。南热带甲烷源和汇是全球甲烷收支的重要组成部分。目前南方甲烷增长速度的主要异常是有记录以来最大的之一。然而，尽管热带甲烷的可变性很重要，但人们对它的研究相对较少。这项提议是为了调查南部热带甲烷的收支情况。这项工作将改善南部热带来源的量化和对突然增长事件机制的理解。南部热带甲烷的来源是多种多样的，每一种都在其产生的甲烷中有自己的同位素特征。湿地在热带南美洲南部和南部亚赤道非洲的西部非常广泛，但关于这些湿地甲烷排放的数据非常稀少。非洲和南美洲稀树草原上的大火也是重要的来源，大型反刍动物种群也是如此。随着最近碳氢化合物的重大发现，人为来源也在增加。热带的俄亥俄州是全球主要的甲烷汇。扬升才是。是一个位置独特的、由英国管理的研究甲烷收支的试验场。在地表，空气几乎总是来自南大西洋中纬度的东南风，在上升后，成为亚马逊的背景空气。在信风逆温的上方，阿森松上空的空气是热带的，其起源在非洲和南美洲之间有规律地切换。目前，皇家霍洛韦支持连续高精度的甲烷和二氧化碳测量(CRDS仪器)，并在阿森松号和东福克兰群岛上对甲烷中的d13C进行烧瓶测量。在方法上，该项目将侧重于测量南部热带地区的甲烷，开展运动研究，特别是在阿森松号上，并对结果进行模拟。测量将包括CRDS在阿森松岛、东福克兰群岛进行的连续测量、RRS JC Ross每两年进行一次的大西洋横断面测量，以及在乌干达、秘鲁和玻利维亚收集CH4和CH4的d13C的特德拉袋样本。活动研究将包括在秘鲁安装一台CRDS仪器，使用无人驾驶航空系统(UAV)在阿森松的贸易逆风上空进行采样，以及开展来源活动，以确定非洲和南美洲甲烷排放的d13C特征。拟议的直升机无人机部署利用了新的专业知识，将代表着英国部署用于大气采样的大型无人机的重要举措。因此，这一部署解决了NERC下一代地球和环境科学平台范围研究中提出的关键科学挑战之一。模拟研究也是最先进的，将包括区域轨迹分析，以评估非洲和南美洲的源输入，以及全球对甲烷的d13C的模拟，并对照项目中的测量结果进行测试。结果将用于评估南热带甲烷在全球预算中的重要性，过去快速变化的原因，以及未来排放快速增长的可能性。

Methane is the second most important greenhouse gas and contributes to the atmospheric chemistry affecting ozone. Southern tropical methane sources and sinks constitute a significant component of the global methane budget. The current major anomaly in southern methane growth rate is among the largest on record. Yet despite its importance, tropical methane variability has received relatively little study. This proposal is to investigate the southern tropical methane budget. The work will improve quantification of southern tropical sources and the understanding of the mechanisms of sudden growth events. Southern tropical methane sources are varied, each having their own isotopic signature in the methane they produce. Wetlands are very extensive in southern tropical S. America and in western parts of southern sub-equatorial Africa, but data on methane emissions from these wetlands are very sparse. Fires in savanna grasslands in Africa and S. America are also significant sources, as are the large ruminant animal populations. Anthropogenic sources are also increasing, with major recent hydrocarbon discoveries. Tropical OH is the major global methane sink. Ascension Is. is a uniquely located, UK-administered, experimental site for studying the methane budget. At surface the air is almost always SE Trade wind, which arrives from the South Atlantic middle latitudes, and, after Ascension, becomes the background air for Amazonia. Above the trade wind inversion, the air over Ascension is tropical, its origin switching regularly between Africa and S. America. Currently Royal Holloway sustains continuous high-precision CH4 and CO2 measurement (CRDS instrument) and also flask measurement of d13C in CH4 on Ascension, as well as on E. Falkland Is. and on RRS JC Ross.Methodologically, the project will focus on the measurement of methane in the southern tropics, carrying out campaign studies, especially on Ascension, and modelling the results. Measurement will include continuous measurement by CRDS in Ascension, E. Falklands, bi-annual Atlantic transects by RRS JC Ross, and Tedlar bag sample collection for CH4 and d13C of CH4 in Uganda, Peru and Bolivia. Campaign studies will include installation of a CRDS instrument in Peru and use of an unmanned aerial system (UAV) to sample above the Trade Wind Inversion on Ascension, as well as source campaigns to characterise d13C signatures of CH4 emissions in Africa and S. America. The proposed helicopter UAV deployment exploits new expertise and would represent an important UK deployment of a substantial UAV for atmospheric sampling. This deployment therefore addresses one of the key science challenges set out in the NERC scoping study for next-generation platforms for Earth & Environmental Science. Modelling studies are also state-of-the-art, and will include regional trajectory analysis to assess source inputs across Africa and S. America, and global modelling of d13C of CH4, tested against the measurements made in the project.The results will be used to assess the importance of southern tropical methane in the global budget, the causes of rapid past changes, and the possibility of future rapid growth in emissions.