Constraining the Past and Future Ocean Sink of Anthropogenic Carbon with Observations

人类活动向大气释放化石燃料二氧化碳被认为是全球气候变化的主要原因。海洋在减轻这种扰动对气候系统的影响方面发挥着至关重要的作用，它隔离了大约三分之一的人为二氧化碳排放。虽然近年来在理解和量化海洋汇方面取得了很大进展，但仍然存在相当大的不确定性，特别是关于二氧化碳排放在海洋和陆地汇之间的分配、海洋化学变化以及未来海洋隔离二氧化碳的能力。在这个项目中，哥伦比亚大学拉蒙特-多尔蒂地球天文台的研究人员将开发和应用一种基于观测的方法来限制过去和未来的人为二氧化碳汇(CANT)。其基本思想是，海洋中的人为二氧化碳扰动可以被视为一种保守的示踪剂，由海洋环流从混合层输送到内陆。这种输运可以用格林函数来描述，它与随时间变化的铁路超高表面浓度卷积，可以用来计算海洋中铁路超高的浓度。基于最大熵方法和来自碳循环模型的启示，逆方法将被用来从观测中估计海洋的格林函数和凸面边界条件，从而产生一种既能解释海洋S复杂的三维环流，又能解释工业时期二氧化碳随时间变化的海气不平衡的方法。智力优势：这项研究将直接导致对人为二氧化碳海洋汇的更好的量化和理解。它的主要成果将是对工业时期海洋中人为二氧化碳的历史、时间演变的分布、吸收和传输进行观测重建，并根据不同的排放情景对未来的吸收进行预测。对这些估计的分析将有助于限制海洋化学的潜在变化，量化海洋和陆地汇的相对作用，并导致对海洋通风在碳循环中的作用的新见解。更广泛的影响：通过提供对人为二氧化碳海洋沉没过去和未来演变的定量估计，拟议的工作与当前更准确地限制人类对气候系统的影响的努力高度相关，气候系统是一个具有社会重要性的问题。作为该项目的一部分，估计的铁路超高区域和绿色功能将免费提供给其他研究人员。格林函数对于从海洋通风到海洋生物地球化学循环的各种问题都将是有价值的。这项研究将有助于研究生的培训和教育，其结果将纳入PI的教学并通过网站更广泛地传播。

The release of fossil fuel CO2 to the atmosphere by human activity has been implicated as the predominant cause of global climate change. The ocean plays a crucial role in mitigating the effects of this perturbation to the climate system, sequestering around a third of anthropogenic CO2 emissions. While much progress has been made in recent years in understanding and quantifying the ocean sink, considerable uncertainties also remain, especially regarding the partitioning of CO2 emissions between the ocean and terrestrial sinks, changes in ocean chemistry, and the future ability of the ocean to sequester CO2.In this project, researchers at the Lamont-Dougherty Earth Observatory of Columbia University will develop and apply an observationally-based approach to constraining the past and future ocean sink of anthropogenic CO2 (Cant). The essential idea is that the anthropogenic CO2 perturbation in the ocean can be treated as a conservative tracer transported by ocean circulation from the mixed layer into the interior. This transport can be described by a Green function, which, convolved with the time-varying surface concentration of Cant, can be used to calculate the concentration in Cant in the ocean. Inverse methods, based on the 'maximum entropy' approach and insights from carbon cycle models, will be used to estimate the ocean's Green function and the Cant surface boundary condition from observations, resulting in an approach that accounts for both the ocean?s complex 3-d circulation and the time-varying air-sea disequilibrium of CO2 over the industrial period.Intellectual merit: This study will directly lead to an improved quantification and understanding of the ocean sink of anthropogenic CO2. Its main outcome will be an observationally-based reconstruction of the historical, time-evolving distribution, uptake, and transport of anthropogenic CO2 in the ocean over the industrial period, and projections for future uptake in response to different emission scenarios. Analysis of these estimates will help constrain potential changes in marine chemistry, quantify the relative roles of the ocean and terrestrial sinks, and lead to new insights into the role of ocean ventilation in the carbon cycle. Broader Impacts: By providing a quantitative estimate of the past and future evolution of the ocean sink of anthropogenic CO2, the proposed work is highly relevant to current efforts to more accurately constrain human impacts on the climate system, an issue of societal importance. Both the Cant fields and Green functions estimated as part of this project will be made freely available to other researchers. The Green functions will be valuable for a variety of problems, ranging from ocean ventilation to marine biogeochemical cycles. This research will contribute to the training and education of a graduate student, and the results will be incorporated into the PI's teaching and disseminated more broadly via a website.