Collaborative Research: Global Estimates of Past and Future Uptake of Anthropogenic Carbon by the Ocean

海洋在受干扰的碳循环中起着至关重要的作用，它吸收了大气中20%至35%的人为二氧化碳排放。然而，在确切的吸收速率及其历史、海洋内人为碳的分布以及气候变化下的未来前景等方面，仍存在相当大的不确定性。在这个项目中，哥伦比亚大学和约翰霍普金斯大学的研究人员将使用“过渡时间分布”（TTD）方法来改进对海洋吸收、库存和人为碳分布（Cant）的估计。在其最一般的形式下，TTD是一个从海洋表面到内部运输的完整描述符。关于TTD的信息可以从瞬态示踪观测中收集到，然后应用于将地表水的估计传播到内部。与其他方法相比，TTD方法具有主要优势，其中包括自然适应运输中的混合，不需要估计海洋碳的生化源和汇，以及能够估计海洋碳的时间演化。TTD方法已与氯氟烃测量一起用于估计全球海洋中的氯氟烃浓度和库存。这些结果纠正了过去估计中的偏差，但是TTD技术仍然可以从进一步的发展中受益。该项目将推广该技术，以包括在全球范围内不断演变的空气-海洋二氧化碳不平衡的影响，这在过去的大多数海洋人为碳研究中都没有考虑到，包括最近基于ttd的全球估计。修正后的方法也将包括多个地表源区域的影响。这些方法的发展将严重依赖于对总循环模型的分析，其中有一个基准（直接模拟的碳）是可用的。改进后的方法将应用于观测，计算整个工业时代和未来全球海洋对二氧化碳的吸收，使用二氧化碳情景。计算将使用恒定的当前海面温度场和历史重建来进行。最后，对碳-气候耦合模式模拟的分析将有助于量化由于忽略海洋环流演化和生物生产力对海洋碳吸收的影响而产生的误差。研究人员预计，该项目将首次以观测为基础，对整个工业时代人类碳吸收的全球分布和演变进行估计。它还将深入了解海洋表面温度、不断变化的循环和生物地球化学循环速率对碳吸收的影响。就更广泛的影响而言，拟议的活动具有社会效益，因为更准确地量化受干扰的碳循环有助于预测气候变化。哥伦比亚大学和约翰霍普金斯大学的研究生将在研究中发挥主要作用，他们将接受海洋运输、碳动力学和数据分析技术方面的高级培训，并将参与教学。研究结果将广泛传播，也将纳入课堂教学。

ABSTRACTOCE-0623366 / OCE-0623423The ocean plays a crucial role in the perturbed carbon cycle, sequestering 20% to 35% of anthropogenic CO2 emissions from the atmosphere. Considerable uncertainty remains, however, as to the precise rate of uptake and its history, the distribution of anthropogenic carbon within the ocean, and the future prospects under changing climate. In this project, researchers at Columbia University and at the Johns Hopkins University will use the "transit-time distribution" (TTD) methodology to improve estimates of oceanic uptake, inventory and distribution of anthropogenic carbon (Cant). In its most general form the TTD is a complete descriptor of transport from the ocean surface to the interior. Information on the TTD can be gleaned from transient tracer observations, and then applied to propagate estimates of surface-water Cant into the interior. Compared to other methods the TTD has key advantages, principle among them a natural accommodation for mixing in transport, the lack of any need to estimate biochemical sources and sinks of ocean carbon, and ability to estimate the time evolution of Cant. The TTD method has been used together with CFC measurements to estimate Cant concentrations and inventories in the global ocean. These results correct biases in past estimates, but the TTD technique can still benefit from further development. This project will generalize the technique to include the effects of evolving air-sea CO2 disequilibrium on a global scale, which is not considered in most past studies of ocean anthropogenic carbon, including the recent TTD-based global estimates. The effects of multiple surface source regions will also be included in the revised method. These methodological developments will rely heavily on analysis of general circulation models, where a benchmark (the directly simulated carbon) is available. The improved method will then be applied to observations to compute the global oceanic uptake of Cant over the full industrial era and into the future, using CO2 scenarios. Calculations will be performed using both constant, present-day sea-surface temperature fields and historical reconstructions. Finally, analysis of coupled carbon-climate model simulations will help quantify the errors incurred by neglecting evolution of ocean circulation and biological productivity on ocean carbon uptake. The investigators anticipate that the project will provide the first observationally-based estimates of the global distribution and evolution of anthropogenic carbon uptake over the full industrial era. It will also provide insight into impact of sea-surface temperatures and changing circulation and biogeochemical cycling rates on the carbon uptake. In terms of broader impacts, the proposed activities are of societal benefit as more accurate quantification of the perturbed carbon cycle feeds into predictions of climate change. Graduate students at Columbia University and Johns Hopkins University will play a major role in the research, will receive advanced training in ocean transport, carbon dynamics and data analysis techniques, and will be involved in teaching. The results of the research will be widely disseminated and will also be included in classroom teaching.