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

甲烷是第二重要的温室气体，对影响臭氧的大气化学有贡献。南部热带甲烷源和汇是全球甲烷收支的重要组成部分。目前南部甲烷增长率的主要异常是有记录以来最大的。然而，尽管它很重要，热带甲烷变异性得到的研究相对较少。这个提议是为了调查南部热带地区的甲烷收支。这项工作将改进对南部热带来源的量化和对突然生长事件机制的理解。南部热带地区的甲烷来源多种多样，每一种甲烷都有自己的同位素特征。在南美洲南部热带地区和非洲南部亚赤道地区的西部地区，湿地非常广泛，但这些湿地的甲烷排放数据却非常稀少。非洲和南美洲热带稀树草原上的大火也是重要的来源，大量的反刍动物也是如此。随着最近油气的重大发现，人为来源也在增加。热带OH是全球主要的甲烷汇。提升。是一个独特的位置，由英国管理，用于研究甲烷预算的实验场所。地面空气几乎总是东南信风，它来自南大西洋中纬度地区，在阿森松升之后，成为亚马逊地区的背景空气。在信风逆温之上，阿森松岛上空的空气是热带的，它的起源经常在非洲和南美洲之间转换。目前，皇家霍洛威在阿森松岛和福克兰群岛上持续进行高精度的CH4和CO2测量（CRDS仪器），并在烧瓶中测量CH4中的d13C。和RRS JC Ross。在方法上，该项目将侧重于测量南部热带地区的甲烷，开展活动研究，特别是在阿森松岛，并对结果进行建模。测量将包括在福克兰群岛东部阿森松岛用CRDS进行连续测量，每两年用RRS JC Ross进行大西洋样带测量，以及在乌干达、秘鲁和玻利维亚用Tedlar袋收集CH4和甲烷的d13C样本。活动研究将包括在秘鲁安装CRDS仪器，使用无人驾驶飞机系统（UAV）在阿森松信风逆温上方取样，以及在非洲和南美开展源活动，以表征CH4排放的d13C特征。拟议的直升机无人机部署利用了新的专业技术，并将代表英国部署一种用于大气采样的重要无人机。因此，这一部署解决了NERC下一代地球与环境科学平台范围研究中提出的关键科学挑战之一。建模研究也是最先进的，将包括区域轨迹分析，以评估整个非洲和南美洲的源输入，以及对CH4 d13C的全球建模，根据项目中进行的测量进行测试。这些结果将被用来评估南部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.