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

北方纬度的变暖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解冻和分解，可能导致甲烷（CH 4）和二氧化碳（CO 2）排放量大幅增加，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温度和海平面变化的全球模型至关重要。在地方一级，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。区域和全球尺度模型的改进需要提高目前对甲烷和二氧化碳通量来源的认识，以深入了解净通量预计将如何对北极变暖作出反应。将飞机产生的通量与当地塔测量值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。直接测量接近地表的区域尺度通量的数据、模型和分析以及使用逆模型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价哪一种环境量和分类量的组合最适合于预测甲烷和二氧化碳排放量，以便根据遥感变量得出更准确的估计数十分重要，还将与现有的碳排放模型进行比较。确定北极北坡和邻近北极沃茨的甲烷和二氧化碳的当前夏末和秋季净通量的能力是建立定量跟踪北极净碳通量的年度时间序列的基准所必需的。在一架小型飞行器上，使用定制的光谱传感器、空气湍流探测器和GPS系统，在10米至10公里的高度上运行，从阿拉斯加北坡采集水和水蒸气（H2O）。该项目弥合了北极地区碳排放的地方研究（如通量塔研究）与反演建模的大区域尺度排放估计之间的规模差距。这项工作提供了与潜在来源相关的已解决的排放量;北极盆地这一部分碳排放综合分析的区域覆盖范围;观测与从小塔测量到卫星遥感的其他观测系统的直接耦合;以及将观测结果与空气传输模型相结合，以将直接排放测量结果与顶部-根据大气层中的剖面测量，减少区域排放量的估计数。具体而言，飞机涡度协方差测量和垂直剖面被用来有效地缩放过程测量短涡度协方差塔的区域尺度，允许确定如何代表某些地区是较大的北坡相对于通量的主要气体，有助于辐射强迫的变化。不同的同位素组成的分子的通量和浓度的观测和建模揭示了关键源过程在当地，景观和区域尺度上的贡献，这是该项目独有的特征。该项目创建了一个分析框架，允许将现场浓度和通量与使用适用于阿拉斯加并广泛适用于其他环极地区的运输模型计算的区域通量相结合。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.