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，并对影响臭氧的大气化学起作用。南方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，尽管其重要性，热带甲烷的变化得到了相对较少的研究。这项建议是调查南部热带甲烷预算。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。南部热带甲烷来源多种多样，每种甲烷都有自己的同位素特征。湿地在热带南部是非常广泛的。美国和非洲南部亚赤道地区的西部湿地，但这些湿地甲烷排放的数据非常稀少。在非洲和南美的热带稀树草原上发生的火灾。美国也是重要的来源，因为是大型反刍动物种群。由于最近发现了重大的碳氢化合物，人为来源也在增加。热带OH是全球主要的甲烷汇。Ascension是一个地理位置独特的，由英国管理的，研究甲烷预算的实验场所。在地面上，空气几乎总是东南信风，来自南大西洋中纬度地区，在Ascension之后，成为亚马逊河流域的背景空气。在信风逆温之上，Ascension上空的空气是热带的，它的起源在非洲和南部之间有规律地转换。美国参考目前，皇家霍洛威公司持续进行高精度CH4和CO2测量（CRDS仪器），并在Ascension和E.福克兰群岛从方法上讲，该项目将侧重于测量南部热带地区的甲烷，开展活动研究，特别是关于Ascension的研究，并对结果进行建模。测量将包括由位于E. Ascension的CRDS进行的连续测量。福克兰群岛，RRS JC Ross一年两次的大西洋断面，以及乌干达、秘鲁和玻利维亚的甲烷和甲烷d13 C的Tedlar袋采样。活动研究将包括在秘鲁安装CRDS仪器，使用无人驾驶航空系统在Ascension信风逆温上空取样，以及在非洲和南美洲开展监测13 C甲烷排放特征的源活动。美国参考拟议的直升机无人机部署利用了新的专业知识，将代表英国部署大量无人机进行大气采样的重要举措。因此，这一部署解决了NERC下一代地球与环境科学平台范围界定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，以评估整个非洲和南非的源输入。结果将用于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排放量未来快速增长的可能性。

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.