Methane Production in the Arctic: Under-recognized Cold Season and Upland Tundra - Arctic Methane Sources-UAMS

在这个项目中，我们将使用最先进的方法和知识，以更好地了解目前的模式和控制甲烷（CH 4）从北极释放到大气中，并改善主要模型，以更好地模拟未来释放的CH 4从北极地球变暖。大气甲烷（CH 4）是第二大温室气体（仅次于CO2），具有很强的人为来源。北方高纬度陆地生态系统占约。50%的热带外生物湿地排放。更重要的是，未来北极的甲烷排放量可能会大幅增加。北极土壤表层3米处的有机碳储量非常大（> 1，300千兆吨碳当量），北极经历和预测的气候变化迅速，因此，本世纪这些土壤真实的可能大量释放生物源甲烷。尽管来自北极的CH 4通量的重要性，但现在和将来，对生物源和总天然CH 4排放的了解很少，建模也很差（Fisher等人，2013年，我们更新了阿拉斯加北极地区的五个涡度相关（EC）塔，使其全年可靠运行并测量CH 4通量。最初的测量产生了两个意想不到的和非常重要的发现：1）冷季CH 4排放量占年排放量的50%以上，2）干燥的高地苔原比潮湿的淹没苔原排放更多的CH 4（Zona等人，2016 PNAS）。这些观测和过程现在没有纳入用于计算北极目前和预测未来甲烷排放量的全球陆地表面/碳循环模型。研究这一新的认识，并将这一认识纳入英国和其他地方使用的模型中，将彻底改变我们准确计算和模拟陆地CH 4通量的能力。这些结果如果得到本项目产出的支持，对于核实目前的基准排放量、检测变化的基准以及有信心地预测北极未来的生物源甲烷排放量至关重要。该项目有两个总体目标：（1）确定寒冷季节和高地冻原在北极CH 4排放中的模式、控制和重要性;（2）将这一认识纳入JULES、LPJ和TCF，从而显著提高我们估计北极当前和预测未来CH 4通量的能力。预计这项工作将通过新的信息和模型开发对政策产生影响，这些信息和模型将通过会议和出版物进行报告，并在即将发布的气专委报告中予以引用。在该项目中，我们将继续全年观测甲烷释放到大气中，以及与这些通量相对应的大气和土壤环境。我们将启动新的实验和观测，以了解控制所观察到的CH 4通量的过程和条件，包括一个新的测量系统，该系统测量CO2，CH 4和222 Rn浓度，允许全年自主确定CH 4的生产，消费和土壤深度和积雪层的通量。我们将全年测量[CH 4]和d13 CH 4，这将有助于确定不同地点和季节表层土壤中甲烷氧化的重要性。我们将确定GPP在控制CH 4生产率方面的作用。我们还将确定维管植物的重要性，在提供一个管道的甲烷产生的深度，逃逸到大气中过去的氧化表面层。这些新信息将为北极社区使用的模型的开发和改进提供信息。这些模型的性能将使用模型开发中未使用的独特数据集进行验证。因此，我们打算UAMS对社区计算当前和有信心地预测未来北极CH 4排放量的能力产生重大影响，从而更好地为政策决策提供信息。

In this project, we will use state of the art approaches and knowledge to better understand the current patterns of and controls on methane (CH4) release from the Arctic to the atmosphere and to improve major models to better simulate future releases of CH4 from the Arctic as the planet warms. Atmospheric methane (CH4) is the second most important greenhouse gas (after CO2) that has strong anthropogenic origins. High northern latitude terrestrial ecosystems account for ca. 50% of extra-tropical biogenic wetland emissions. More importantly methane emissions from the Arctic could increase dramatically in the future. The very large organic carbon stocks (>1,300 GtC) in the top 3 m of Arctic soils and the rapid climate change experienced and predicted in the Arctic, results in a very real possibility of large biogenic CH4 release from these soils in this century. Despite the importance of CH4 fluxes from the Arctic, now and in the future, biogenic and total natural CH4 emissions are poorly understood and very poorly modelled (Fisher et al., 2014).In 2013, we updated five eddy covariance (EC) towers in Arctic Alaska to operate reliably year-round and measure CH4 fluxes. Initial measurements yielded two unexpected and highly significant findings: 1) cold season CH4 emissions account for >50% of annual emissions and 2) drier upland tundra are larger emitters of CH4 than wetter inundated tundra (Zona et al 2016 PNAS). These observations and processes are not now incorporated in leading global land-surface/carbon-cycle models used to calculate current and predict future CH4 emissions from the Arctic. Verifying this new understanding and incorporating this understanding into models used in the UK and elsewhere will revolutionize our ability to accurately calculate and model terrestrial CH4 fluxes. These results, if supported by the outputs of this project, are critical to verifying current baseline emissions, detecting a changing baseline, and for predicting, with confidence, biogenic CH4 emissions from the Arctic in the future. This project has two overarching objectives: (1) determining the patterns of, controls on, and importance of cold season and upland tundra in Arctic CH4 emissions; (2) incorporating this understanding into JULES, LPJ and TCF, thus significantly improving our ability to estimate current and predict future CH4 fluxes in the Arctic. This work is expected to impact policy through new information and model development, reported through conferences and publications and referenced in upcoming IPCC reports. In the project, we will continue year-round observation of methane release to the atmosphere, and the atmospheric and soil environment that corresponds to these fluxes. We will initiate new experiments and observations to understand the processes and conditions controlling the observed CH4 fluxes including a new system of measurement of CO2, CH4, and 222Rn concentrations that allow autonomous, year-round, determination of CH4 production, consumption, and flux by soil depth and snow layer. We will measure year-round [CH4] and d13CH4 will help identify the importance of methane oxidation in surface soil layers at different locations and seasons. And we will determine the role of GPP in controlling rates of CH4 production. We will also determine the importance of vascular plants in providing a conduit for CH4 produced at depth, to escape to the atmosphere past an oxidizing surface layer. This new information will inform model development and improvement of models used by the Arctic community. Performance of these models will verified with unique data sets not used in model development. As a result, we intend UAMS to have a major impact on the communities' ability to calculate current and to predict with confidence future Arctic CH4 emissions in a changing world and thereby better inform policy decisions.