Collaborative Research: Diagnosing Eddy mixing in DIMES

合作研究：诊断 DIMES 中的涡流混合

• 批准号: 1233598
• 负责人: W. Brechner Owens
• 金额: $ 9.99万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1233598&HistoricalAwards=false
• 关键词: Collaborative; Research; Diagnosing; Eddy; mixing

Climate-scale ocean models unanimously stress the key regulatory function played by the oceanic overturning circulation in the Earth's climate and biogeochemical cycles over decadal and longer time scales. Yet in their quest to resolve many topical climate problems, the models' credibility is challenged by their extreme sensitivity to the representation of mixing processes in the Southern Ocean. This peculiarity of model behavior reflects the unique role of mixing in mediating the vertical and horizontal transports of water masses in the Antarctic Circumpolar Current (ACC), which shape the overturning circulation through their respective impacts on the overturning rate and inter-ocean exchange. The Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) has collected a wealth of data to quantify mixing, including the spreading of a chemical tracer and of 150 floats at two different depths. The goal of this proposal is to analyze the tracer and float data to estimate the vertical and horizontal variations in lateral eddy mixing. The principal investigators' previous work has shown that tracer and floats are, by themselves, insufficient to accurately constrain these variations. Therefore the data will be analyzed together with surrogate tracers and floats advected with a numerical simulation of the regions under study.Intellectual Merit: This project tackles the formidable problem of quantifying the role of small-scale eddies in the large-scale circulation. Because these eddies are so challenging to observe and model, it is difficult to quantify their large-scale effect. Indeed the ocean uptake of heat and carbon over the next century in climate models can be very different in models that parameterize mesoscale eddies compared to models that explicitly resolve them. This implies that present parameterizations, which either ignore or improperly represent the horizontal and vertical variations in mesoscale eddy mixing, may not have the skill to make accurate climate projections. The goal of this project is to ground new understanding of eddy mixing in data and use these results to develop new parameterizations for climate models. The connection between data and models is key to ensure that the DIMES experiment will have a long term legacy in the climate community.Broader Impacts: This project addresses the important problem of quantifying mixing by eddies in the ocean and their role in the climate system. Furthermore the work should be seen in the wider context of studies of eddy-mean flow interaction in turbulent flows. The ideas have importance for the general circulation of the atmosphere and of planetary atmospheres, particularly those of the gas giants such as Jupiter. Indeed, parametrically, the ocean is closely akin to Jupiter, with an eddy scale that is hundreds of times smaller than that of the large-scale circulation. Finally, there is a strong educational component through the training of three graduate students and two post-docs, and the development of new curricula to introduce students in the MIT/WHOI Joint Program to the role of the Southern Ocean in the climate system.The DIMES project is a process study sponsored by the U.S. CLIVAR (climate variability and predictability) program.

气候尺度海洋模式一致强调海洋翻转环流在年代际和更长时间尺度上对地球气候和生物地球化学循环发挥的关键调节作用。然而，在解决许多局部气候问题的过程中，这些模式的可信度受到了挑战，因为它们对南大洋混合过程的表现极为敏感。模式行为的这种特殊性反映了混合在调节南极环极流（ACC）水团垂直和水平输送中的独特作用，它们通过各自对翻转速率和海洋间交换的影响来塑造翻转环流。南大洋的横旋流和等旋流混合实验（DIMES）收集了大量的数据来量化混合，包括化学示踪剂的扩散和在两个不同深度的150个浮标。本文的目标是分析示踪剂和浮子的数据，以估计横向涡流混合的垂直和水平变化。主要研究人员先前的工作表明，示踪剂和漂浮物本身不足以准确地限制这些变化。因此，数据将与替代示踪剂和漂浮物一起进行分析，并对研究区域进行数值模拟。知识价值：这个项目解决了量化小规模漩涡在大规模循环中的作用的棘手问题。因为这些涡流很难观察和建模，所以很难量化它们的大规模效应。事实上，在气候模式中，下个世纪海洋对热量和碳的吸收，在参数化中尺度涡旋的模式中，与明确解决它们的模式相比，可能会有很大的不同。这意味着，目前的参数化要么忽略，要么不恰当地表示中尺度涡旋混合的水平和垂直变化，可能不具备做出准确气候预估的能力。该项目的目标是在数据中建立对涡旋混合的新认识，并利用这些结果为气候模式开发新的参数化。数据和模型之间的联系是确保DIMES实验将在气候界留下长期遗产的关键。更广泛的影响：该项目解决了量化海洋漩涡混合及其在气候系统中的作用的重要问题。此外，这项工作应该在紊流中涡流-平均流相互作用研究的更广泛背景下进行。这些观点对大气和行星大气的总体循环，特别是像木星这样的气态巨行星的大气，具有重要意义。事实上，从参数上讲，海洋与木星非常相似，涡旋的规模比大尺度环流的规模小几百倍。最后，通过培训三名研究生和两名博士后，以及开发新课程，向麻省理工学院/世卫组织联合项目的学生介绍南大洋在气候系统中的作用，这是一个强有力的教育组成部分。DIMES项目是由美国CLIVAR（气候变率和可预测性）项目赞助的一项过程研究。