Collaborative Research: Bridging the scale gap between local and regional methane and carbon dioxide isotopic fluxes in the Arctic

合作研究：缩小北极当地和区域甲烷和二氧化碳同位素通量之间的规模差距

• 批准号: 1848694
• 负责人: Mark Heuer
• 金额: $ 58.18万
• 依托单位: Oak Ridge Associated Universities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-01-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1848694&HistoricalAwards=false
• 关键词: Collaborative; Research; Bridging; scale; gap

Northern latitudes are warming at twice the global mean, making carbon stored in permafrost increasingly vulnerable to thaw and decomposition by microbes, potentially leading to large increases in methane (CH4) and carbon dioxide (CO2) emissions, both important greenhouse gases. Accurate and reliable forecasts of greenhouse gas emissions are critical for the improvement of global models that predict changes to temperature and to sea level. On a local level, the data and modeling products can be used to better inform local populations of the changes happening to their environment and help predict likely changes in the future. Improvements to regional and global scale models require advancement in the current knowledge of methane and carbon dioxide flux sources to gain insight into how the net flux is expected to respond to a warming Arctic. Comparing aircraft derived fluxes to local tower measurements and land classification maps allows for the determination of which mechanisms are primarily responsible for the variation in emissions. Data, models, and analysis directly measuring the fluxes over regional scales close to the surface and measuring fluxes using inverse modeling helps to better understand the differences. Data generated from this project are important for evaluating which combination of environmental quantities and categorical quantities are best suited for predicting methane and carbon dioxide emissions to produce more accurate estimates from remotely sensed variables and will also be compared with existing carbon emissions models. The ability to define the current late summer and autumn net flux of methane and carbon dioxide from the North Slope and adjoining Arctic waters is required to establish a benchmark for quantitatively tracking the annual time series of net carbon flux from the Arctic.This research provides emission measurements of CO2 and CH4 plus nitrous oxide (N2O), and water vapor (H2O) from the North Slope of Alaska on a small aircraft operating at altitudes from 10 m to 10 km, with custom-built spectroscopic sensors, an air turbulence probe, and GPS systems. This project bridges the scale gap between local studies of carbon emissions in the Arctic, such as those from flux towers, and large regional scale emissions estimates from inversion modeling. The work provides resolved emissions correlated with underlying sources; regional coverage for comprehensive analysis of carbon emissions in this part of the Arctic basin; direct coupling of the observations with other observing systems ranging from small tower measurements to satellite remote sensing; and coupling of the observations to an air transport model to compare direct emission measurements to top-down estimates of regional emissions based on profile measurements in the atmosphere. Specifically, aircraft eddy covariance measurements and vertical profiles are used to effectively scale process measurements from short eddy covariance towers to the regional scale, allowing for determining how representative certain areas are of the larger North Slope with respect to flux of the major gases that contribute to changes in radiative forcing. Observations and modeling of fluxes and concentrations of molecules that differ in their isotopic composition reveal the contributions of key source processes at local, landscape, and regional scale, a feature unique to this project. This project creates an analysis framework to allow for the combination of in situ concentrations and fluxes with regional fluxes calculated using a transport model that both is adapted for Alaska and widely applicable to other circumpolar areas.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

北纬地区的变暖速度是全球平均水平的两倍，使得永久冻土中储存的碳越来越容易被微生物解冻和分解，从而可能导致甲烷（CH4）和二氧化碳（CO2）排放量大幅增加，这两种气体都是重要的温室气体。准确可靠的温室气体排放预测对于改进预测温度和海平面变化的全球模型至关重要。在地方层面，数据和建模产品可用于更好地告知当地居民其环境发生的变化，并帮助预测未来可能发生的变化。区域和全球规模模型的改进需要提高当前对甲烷和二氧化碳通量来源的了解，以深入了解净通量预计将如何应对北极变暖。将飞机产生的通量与当地塔测量和土地分类图进行比较，可以确定哪些机制是造成排放变化的主要原因。数据、模型和分析直接测量靠近地表的区域尺度上的通量并使用逆向建模测量通量有助于更好地理解差异。该项目生成的数据对于评估哪种环境量和分类量的组合最适合预测甲烷和二氧化碳排放量非常重要，以便根据遥感变量产生更准确的估计，并将与现有的碳排放模型进行比较。需要能够定义当前夏末和秋季来自北坡和毗邻北极水域的甲烷和二氧化碳净通量，才能建立定量跟踪来自北极的净碳通量年度时间序列的基准。本研究提供了阿拉斯加北坡的 CO2 和 CH4 加一氧化二氮 (N2O) 和水蒸气 (H2O) 的排放测量。 小型飞机在 10 m 至 10 km 的高度运行，配备定制光谱传感器、空气湍流探测器和 GPS 系统。该项目弥合了北极碳排放的当地研究（例如通量塔的碳排放）与反演模型的大区域碳排放估算之间的规模差距。这项工作提供了与潜在来源相关的已解决的排放量；区域覆盖，对北极盆地这一部分的碳排放进行综合分析；将观测结果与从小塔测量到卫星遥感等其他观测系统直接耦合；将观测结果与航空运输模型相结合，将直接排放测量结果与基于大气剖面测量结果的自上而下的区域排放估计结果进行比较。具体来说，飞机涡流协方差测量和垂直剖面用于有效地将过程测量从短涡流协方差塔缩放到区域尺度，从而确定较大北坡的某些区域在导致辐射强迫变化的主要气体通量方面的代表性。对同位素组成不同的分子通量和浓度的观测和建模揭示了关键源过程在局部、景观和区域尺度上的贡献，这是该项目的独特特征。该项目创建了一个分析框架，允许将原位浓度和通量与使用传输模型计算的区域通量相结合，该模型既适用于阿拉斯加，又广泛适用于其他极地地区。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。