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

北纬地区变暖的速度是全球平均水平的两倍，这使得储存在永久冻土中的碳越来越容易被微生物融化和分解，这可能会导致甲烷(CH4)和二氧化碳(CO2)排放大幅增加，这两种气体都是重要的温室气体。准确和可靠的温室气体排放预测对于改进预测气温和海平面变化的全球模型至关重要。在地方层面上，数据和建模产品可以用来更好地向当地居民通报环境发生的变化，并帮助预测未来可能发生的变化。要改进区域和全球尺度的模式，就需要提高目前对甲烷和二氧化碳通量来源的了解，以便深入了解净通量预计将如何应对北极变暖。将飞机得出的通量与当地的塔楼测量和土地分类图进行比较，可以确定哪些机制对排放量的变化负有主要责任。数据、模型和分析直接测量接近地表的区域尺度上的通量，并使用逆模拟来测量通量，有助于更好地理解差异。该项目产生的数据对于评估环境数量和类别数量的哪种组合最适合预测甲烷和二氧化碳排放非常重要，以便从遥感变量得出更准确的估计，并将与现有的碳排放模型进行比较。要确定北坡和邻近北极水域当前夏末和秋季甲烷和二氧化碳净通量的能力，就必须建立一个基准，以定量跟踪北极净碳通量的年度时间序列。这项研究提供了阿拉斯加北坡二氧化碳、甲烷和一氧化二氮(N2O)以及水蒸气(H2O)的排放测量，该飞机在10米至10公里的高度运行，配备定制的光谱传感器、空气湍流探测器和GPS系统。该项目弥合了北极碳排放的地方性研究(如通量塔的研究)与通过逆模型进行的大规模区域排放估计之间的规模差距。这项工作提供了与基本来源相关的已解决排放量；北极盆地这一部分碳排放综合分析的区域覆盖范围；观测与其他观测系统的直接耦合，从小塔测量到卫星遥感；观测与空中运输模型的耦合，以将直接排放测量与根据大气剖面测量自上而下地估计的区域排放量进行比较。具体地说，飞机涡旋协方差测量和垂直剖面被用来有效地将过程测量从短的涡旋协方差塔扩大到区域尺度，从而能够确定某些区域相对于促成辐射强迫变化的主要气体的通量在多大北坡具有多大的代表性。对不同同位素组成的分子的通量和浓度的观察和建模揭示了当地、地貌和区域尺度上的关键来源过程的贡献，这是该项目所独有的特征。该项目创建了一个分析框架，以允许将现场浓度和通量与使用运输模型计算的区域通量相结合，该模型既适用于阿拉斯加，也广泛适用于其他环极地地区。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.