A Modeling and Data Study of Dissolved Oxygen and pCFC Age Variability in the Thermocline of the Southern Ocean

最近对重复占据水文断面期间的溶解氧的观察发现，南印度、南太平洋和澳大利亚南部的温跃层内的表观氧利用率增加。这项拟议研究的目的是确定变化在物理过程或生物过程中的作用，这些过程或生物过程导致南大洋温跃层内溶解氧的变化，包括亚南极模式和南极中间水域。世界海洋环流实验(WOCE)和气候可变性和可预测性(CLIVAR)重复水文计划的数据分析将与使用Hallberg等温模式的可变物理强迫的模式模拟相结合。这些研究将包括氯氟化碳(CFCs)。如果在重复测量期间可以获得氟氯化碳测量，则pCFC年龄的增加与温跃层内氧气的减少是同一位置的。由于氯氟烃不受生物过程的可变性影响，它们的分布意味着物理强迫的可变性导致了表观氧利用率的增加。模拟研究将确认南大洋是否也是如此，并将用来确定由于风的变化、表面浮力强迫和气体交换对南大洋温跃层和模式水域的通风和环流的物理强迫的变异性的相对重要性。对北太平洋的类似研究表明，同样的模型再现了从20世纪80年代到90年代观测到的深层温跃层中氧气的减少。由于模型的保真度，整个流域的结果可以用来提供所观察到的变化的背景。在这项工作中，通风的变化已被证明在所讨论的水团形成区域附近是重要的，而环流变化在更远的下游更重要。拟议工作的更广泛影响该项目的结果将有助于解释CLIVAR重复水文法期间的二氧化碳系统测量结果。确定人为二氧化碳浓度的分数碳法依赖于稳态环流假设，然后利用表观氧利用(AOU)修正了再矿化作用，并使用pCFAGE修正了海-气不平衡。很明显，在计算碳吸收时，需要考虑物理强迫的可变性。一名氯氟化碳化学家和一名物理海洋学家的密切合作应该会为这一重要问题提供新的见解。此外，将继续与GFDL的建模小组合作，使他们在解释观测数据方面的建模工作扎根于基础。该项目还将促进开发Hallberg等生物化学模型的生物地球化学部分，并将与全球地球物理研究中心合作，向社区提供离线示踪剂平流代码。两名博士后研究员和一名研究生将接受这一跨学科研究项目的培训。国际海洋学联合会将继续参与支持物理海洋学领域的妇女的工作，方法是在国家海洋学基金会和海洋科学研究所的支持下，为该领域的初级妇女建立一个辅导网络。

0525874Intellectual MeritRecent observations of dissolved oxygen during repeat occupations of hydrographic sections have found increased apparent oxygen utilization within the thermocline of the South Indian, South Pacific, and south of Australia. The goal of this proposed research is to identify the role of variability in the physical processes or biological processes which result in changes in dissolved oxygen within the Southern Ocean thermocline, including Subantarctic Mode and Antarctic Intermediate Waters. Data analysis of the World Ocean Circulation Experiment (WOCE) and CLImate VARiability and predictability (CLIVAR) Repeat Hydrography Programs will be combined with model simulations with variable physical forcing using the Hallberg Isopycnal Model. Chlorofluorocarbons (CFCs) will be included in these studies. Where CFC measurements are available during repeat measurements, increases in the pCFC ages are co-located with the decreases in oxygen within the thermocline. Since CFCs are not affected by variability in biological processes, their distributions imply that variability in the physical forcing has produced the increased apparent oxygen utilization. The modeling study will confirm whether this is true as well in the southern ocean and will be used to determine the relative importance of the variability in physical forcing due to variability in the winds, surface buoyancy forcing, and gas exchange on the ventilation and circulation of the thermocline and mode waters of the Southern Ocean. Similar studies of the North Pacific have shown that the same model reproduces the observed decreases of oxygen in the deep thermocline from the 1980s to the 1990s. Because of the fidelity of the model, the basin wide results can be used to provide a context for the observed changes. In that work, changes in ventilation have been shown to be important near the formation region of the water mass in question, while circulation changes were more important further downstream. Broader Impacts of Proposed WorkThe results from this project will contribute to the interpretation of the carbon dioxide system measurements during the CLIVAR Repeat Hydrography. The fractional carbon method for determination of the anthropogenic carbon dioxide concentration relies on the assumption of steady state circulation, and then corrects for remineralization using Apparent Oxygen Utilization (AOU) and for air-sea disequilibrium using pCFC ages. It is clear that variability in physical forcing needs to be considered in the calculation of carbon uptake. The close collaboration of a CFC chemist and a physical oceanographer should provide new insight into this important problem. In addition, collaborations with the modeling group at GFDL will be continued to ground their modeling effort in interpretation of observations. The project will also contribute to the development of the biogeochemical component of the Hallberg Isopycncal Model and will make the offline tracer advection code available to the community in collaboration with GFDL. Two post-doctoral fellows and a graduate student will receive training in this interdisciplinary research project. The co-PI will continue to be involved in supporting women in physical oceanography through an effort supported by NSF and ONR to developing a mentoring network for junior women in the field.