Wetland contribution to interannual variability in atmospheric methane growth rate

甲烷(CH4)是人类社会的重要能源，但也是一种能够改变地球气候的强有力的温室气体。对自然和人类向大气中排放的甲烷进行量化是具有挑战性的，但为了让各国核实是否实现了减少温室气体排放的目标，这是必要的。沼泽、沼泽、沼泽和沼泽等湿地是向大气排放甲烷的最大自然来源。在前工业时代，自然湿地是地球大气中甲烷的主要来源，并继续是甲烷的关键常年来源，形成了人类甲烷排放叠加的自然大气背景，必须加以识别。甲烷中碳和氢的重同位素和轻同位素的细微差异可以用来确定不同来源的排放，包括不同类型的湿地。可靠的污染源识别增强了我们量化区域和全球排放源年复一年变化的能力。它还能够检测来源的变化，如湿地等巨大的全球生态系统是否正在以一种可能进一步增加地球大气中甲烷和二氧化碳数量的方式对气候变化做出反应。*湿地中同位素变化的自然模式仍在出现，特别是氢同位素，由于分析方面的挑战，迄今尚未对其进行广泛研究。这项研究计划将使用新的激光仪器，这是加拿大第一个此类仪器，用于同时测量湿地地下的碳和氢同位素组成及其向大气的排放。将确定甲烷排放的同位素组成与湿地类型之间的关系。还将描述环境变量的影响以及改变甲烷中同位素比率的气体运输过程的作用。这些数据将被整合到全球模型中，以改进对湿地对大气甲烷浓度的贡献的估计，并提高对湿地在影响地球大气中甲烷增加速度的年复一年变化方面所起的作用的理解。对这些重要自然生态系统的排放有更详细的了解，将能够更准确地量化人类活动，特别是生物来源的甲烷排放，因为目前仅使用碳同位素无法明确地识别它们的排放。开发基于稳定碳和氢同位素的双同位素方法将提供不那么含糊的来源特征，并有助于完善全球甲烷循环预算。

Methane (CH4) is an important energy source for human society but also a potent greenhouse gas capable of altering Earth's climate. Quantifying natural and human release of methane to the atmosphere is challenging but necessary in order for nations to verify that targets are being met for reducing greenhouse gas emissions. *** Wetlands such as bogs, fens, marshes and swamps are the largest natural source of methane emissions to the atmosphere. During pre-industrial times, natural wetlands were the dominant source of methane in Earth's atmosphere and continue to be a key perennial source of methane that forms the natural atmospheric background on which human methane emissions are superimposed and must be discerned. Subtle differences in the quantities of heavy and light isotopes of carbon and hydrogen in methane can be used to 'fingerprint' emissions from different sources, including different types of wetland. Reliable identification of sources enhances our ability to quantify year-to-year changes in emission sources both regionally and globally. It also enables detection of change in sources such as whether vast global ecosystems like wetlands are responding to climate change in a manner that may further increase the amount of methane and carbon dioxide in Earth's atmosphere. *** Natural patterns of isotopic variation in wetlands are still emerging, in particular for hydrogen isotopes, which have not been studied extensively to date because of analytical challenges. This program of research will employ new laser instrumentation, the first of its type in Canada, to measure both carbon and hydrogen isotope compositions simultaneously in the subsurface of wetlands and their emissions to the atmosphere. Relationships between the isotope composition of methane emissions and wetland type will be determined. The influence of environmental variables and the role of gas transport process that alter isotope ratios in methane also will be characterized. The data will be integrated into global models to refine estimates of the contribution of wetlands to the atmospheric concentration of methane and to improve understanding of the role that wetlands play in influencing year-to-year changes in the rate at which methane is increasing in Earth's atmosphere. A more detailed knowledge of emissions from these important natural ecosystems will enable more accurate quantifications of methane release from human activities, in particular, biological sources because their emissions at present cannot be fingerprinted' unambiguously using only carbon isotopes. Development of a dual isotope approach based upon both stable carbon and hydrogen isotopes will provide less ambiguous source signatures and help to refine the global methane cycle budget.