Collaborative Research: New Diagnostics of Water-Mass Ventilation Estimated from Tracer Data

通风率量化了海洋如何在从月到千年的时间尺度上与气候系统的其他部分进行交流，并确定了海洋缓冲大气层免受气候异常影响的能力，以及吸收大气痕量气体的能力，包括人为二氧化碳。根据最近的研究，新通风的水的表面通量必须根据水在海洋内部的停留时间进行划分，以正确描述瞬态示踪剂的库存如何随时间演变，因此通风率是一个分布，而不是像到目前为止被认为是足够的，一个单一的数字代表一个整体通量。这从根本上改变了估计问题的反卷积的通风率分布，传播已知的混合层浓度测量internal values.Oceanographers从哥伦比亚大学和加州大学欧文分校的建议，使用CFC，氚，放射性碳瞬态示踪剂数据，连同网格的温度，盐度，营养和氧的数据，估计的通风率分布的海洋。将对一系列密度类别的通风率分布进行系统的估计，这些密度类别的露头覆盖了全球大部分海洋表面。拟议工作的一个主要部分将是一个严格的量化的不确定性，由于数据中的错误，并由于欠定性质的deconvolutions.Two deconvolutionsmethod将采用：一个测试参数的方法和一个新的applicationof的最大熵方法。通风率分布的反褶积将受到CFCs、氚和炸弹放射性碳在十年时间尺度上的限制，并受到背景放射性碳在更长时间尺度上的限制。稳定示踪剂将限制通风率分布的空间和季节依赖性。最大熵反演将使用最先进的数据同化模型来产生通风率分布的先验猜测。该模型还将用于生成真实的合成示踪剂数据，以量化参数解卷积和最大熵解卷积的系统误差。该研究将提供一个新颖的全面图像，说明海洋如何在数月到数千年的时间尺度上与大气交流，并帮助协调之前基于不完整的整体通量图对通风量的不同估计。拟议的研究将提供第一个全球估计通风-当前海洋状态的速率分布及其不确定性的基线估计，以便将来对通风中的变率和气候变化的估计可以有意义的评价。拟议的工作将与关于限制海洋吸收人为碳的气候研究产生协同作用。将向社区提供一个使用最大熵方法进行广义水团分析的MATLAB工具箱。除了主要的科学贡献，拟议的工作将提供资金，以支持博士后学者的职业发展，并为研究生提供海洋运输诊断，数据分析技术，海洋建模和分析海洋在气候系统中的作用的教育和培训。

Ventilation rates quantify how the ocean communicates with the rest of the climate system on timescales ranging from month to millennia, and determine the ocean's ability to buffer the atmosphere from climate anomalies and to take up atmospheric trace gases, including anthropogenic carbon dioxide. Based on recent research that surface fluxes of newly-ventilated water must be partitioned according to the water's residence time in the ocean interior in order to describe correctly how inventories of transient tracers evolve with time, ventilation rate is therefore a distribution and not, as had been thought sufficient until now, a single number representing a bulk flux. This fundamentally changes the estimation problem to a deconvolution for a ventilation-rate distribution that propagates known mixed-layer concentrations to measured interior values.Oceanographers from Columbia University and University of California at Irvine propose to use CFC, tritium, and radiocarbon transient tracer data, together with gridded temperature, salinity, nutrient, and oxygen data, to estimate the ventilation-rate distributions of the ocean. The ventilation-rate distributions will systematically be estimated for a range of density classes whose outcrops cover most of the global ocean surface. A major part of the proposed work will be a rigorous quantification of the uncertainties due to errors in the data and due to the underdetermined nature of the deconvolutions.Two deconvolution methods will be employed: A tested parametric approach and a novel applicationof the maximum-entropy method. The deconvolution of the ventilation-rate distribution will be constrained on decadal timescales by CFCs, tritium and bomb radiocarbon and by the background radiocarbon on longer timescales. Steady tracers will constrain the ventilation-rate distribution's spatial and seasonal dependence. The maximum-entropy inversions will use a state-of-the-art data-assimilation model to produce a prior guess for the ventilation-rate distribution. This model will also be used to generate realistic synthetic tracer data to quantify the systematic errors of both the parametric and the maximum-entropy deconvolutions. The research will provide a novel comprehensive picture of how the ocean communicates with the atmosphere on timescales of months to millennia and help reconcile disparate previous estimates of ventilation based on the incomplete bulk-flux picture.The proposed research will provide the first global estimate of the ventilation-rate distribution for the current state of the ocean and a baseline estimate of its uncertainty so that future estimates of variability and climate change in ventilation can meaningfully be assessed. The proposed work will be synergistic with climate research on constraining the oceanic uptake of anthropogenic carbon. A MATLAB toolbox for performing generalized water-mass analysis using the maximum entropy method will be made available to the community. In addition to the primary scientific contributions, the proposed work will provide funding to support the career development of a postdoctoral scholar, and education and training for graduate students in ocean transport diagnostics, data analysis techniques, ocean modeling, and in analyzing the ocean's role in the climate system.