Collaborative Research: Estimating the Indian Ocean overturn and diapycnal mixing

合作研究：估计印度洋翻转和地幔混合

• 批准号: 0926651
• 负责人: Alison Macdonald
• 金额: $ 30.65万
• 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: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0926651&HistoricalAwards=false
• 关键词: Collaborative; Research; Estimating; Indian; Ocean

The Indian Ocean has multiple roles in the global overturning circulation and carbon cycle, including throughput and transformation of Indonesian Throughflow Water, upwelling of deep and bottom waters from the Atlantic and Southern Ocean, and diffusive production of deep, intermediate and thermocline waters fed by this upwelling. Decadal change in South Indian ventilation and upper ocean overturn has been demonstrated. This project aims to:(1) Improve estimates of the Indian Ocean overturning circulation and diapycnal mixing, and the associated carbon and nutrient budgets. Modern, comprehensive data analysis and a high resolution GCM will be used to interpret and narrow the wide range of current estimates.(2) Characterize regional (basin-oriented, east-west, equatorial) distributions of mixing and overturn, affected by the complex basin geometry and by forcing that is strongly variable in both space and time; determine how these inhomogeneities impact carbon, anthropogenic carbon, oxygen, freshwater and heat transports and divergences.(3) Analyze changes in overturning circulation at 32°S from 1987 through 2009. Compute mass, heat, freshwater, CO2, oxygen and nutrient budgets from the 32°S section being collected in spring 2009; compare with previous occupations, and analyze in light of changes in the wind and buoyancy forcing (including the Southern Annular Mode).Three complementary approaches will be used for estimating basin-wide circulation, overturn and mixing: (1) analysis of the Indian Ocean portion of two state estimates of the circulation, temperature and salinity (ECCO and the related high resolution SOSE); (2) analysis of the chemical and physical data from WOCE/JGOFS sections, and repeat sections at 32S for 1987, 2002, (1995) and 2009 using inverse techniques; and (3) analysis of overturn and diapycnal mixing in the high resolution POP model, which has recently been run with tracers. The project will include analysis of the mean and the seasonal (monsoonal) circulation. Carbon transports will be compared to previous observation-based results and to the results from OCMIP models.Intellectual Merit: The proposed work is unique in that it will focus on the geographic distribution of diapycnal processes in the Indian Ocean, thus elucidating the dominant physical mechanisms. It will provide a comparison and combination of results from three different approaches: state estimation, suited to broad-scale, frequent sampling; analysis of highly-resolved synoptic sections with full chemistry, suited to detailing property budgets; and high resolution OGCM results using observed forcing, suited to studying dynamical processes. The project will be the first to use the WOCE/JGOFS fields to relate the details of ocean circulation, overturn and mixing to the location and magnitude of Indian Ocean CO2 uptake and outgassing, thereby connecting source/sinks regions to asymmetries in overturn and mixing. This project will also contribute to study of decadal change in the south Indian through analysis of the 2009 32S repeat hydrographic section, which is being collected by the U.S. Repeat Hydrography/CO2 program, which in itself does not provide funding for analysis.Broader Impacts: Estimates of oceanic CO2 uptake are necessary for accurate prediction of future atmospheric CO2 content; direct estimates of inorganic carbon flux divergences will provide a constraint on the estimates made through surface pCO2 measurements and numerical models. Ventilation and overturn changes in the subtropical Indian Ocean have been demonstrated and this project will extend the decadal time series to 2009. A graduate student will be supported (SIO). A workshop on ocean circulation and climate change for 25 middle-school teachers will be developed (Talley). Oceanography projects with students and teachers at local schools will be continued (Macdonald). Ocean modeling and use in coupled climate models will be presented at a teachers' workshop at SFSU (McClean).

印度洋在全球翻转环流和碳循环中具有多重作用，包括印度尼西亚洋流的吞吐量和转化，大西洋和南大洋深层和底层沃茨的上涌，以及由这种上涌补给的深层、中层和温跃层沃茨的扩散生产。在南印度通风和上层海洋翻转的十年变化已经得到证明。该项目旨在：（1）改进对印度洋翻转环流和底辟混合以及相关碳和营养物收支的估计。将使用现代综合数据分析和高分辨率的大气环流模式来解释和缩小目前估计数的范围。(2)表征区域（盆地导向，东西，赤道）分布的混合和翻转，受复杂的盆地几何形状和强迫，是强烈的变化在空间和时间;确定这些不均匀性如何影响碳，人为碳，氧，淡水和热量的传输和分歧。(3)分析1987年至2009年32°S翻转环流的变化。计算2009年春季收集的32°S剖面的质量、热量、淡水、CO2、氧气和营养物收支;与以前的作业进行比较，并根据风和浮力作用力的变化进行分析（包括南部环形模式）。将使用三种互补的方法来估计全流域的环流、翻转和混合：（1）分析两个国家印度洋部分的环流、温度和盐度估计数（ECCO和相关的高分辨率SOSE）;（2）利用反演技术分析了1987、2002、1995和2009年WOCE/JGOFS剖面和32 S重复剖面的化学和物理数据;（3）最近用示踪剂运行的高分辨率POP模式中的翻转和底辟混合分析。该项目将包括分析平均和季节（季风）环流。碳运输将比较以前的观测结果和OCMIP models.Intellectual优点的结果：拟议的工作是独一无二的，因为它将专注于在印度洋的diapycnal过程的地理分布，从而阐明占主导地位的物理机制。它将提供三种不同方法的结果的比较和组合：状态估计，适合于大规模，频繁的采样;分析高分辨率的天气剖面与完整的化学，适合于详细的财产预算;和高分辨率OGCM结果使用观察到的强迫，适合于研究动力学过程。该项目将是第一个利用海洋环流实验/联合全球海洋观测FS场将海洋环流、翻转和混合的细节与印度洋二氧化碳吸收和释气的位置和幅度联系起来的项目，从而将源/汇区域与翻转和混合的不对称联系起来。该项目还将通过分析2009年32 S重复水文剖面，促进对南印度十年变化的研究，该剖面由美国重复水文/CO2方案收集，该方案本身并不提供分析资金。对无机碳通量差异的直接估算将对通过地表pCO 2测量和数值模型进行的估算造成限制。在亚热带印度洋的通风和翻转的变化已经证明，这个项目将延长到2009年的十年时间序列。研究生将得到支持（SIO）。将为25名中学教师举办海洋环流和气候变化讲习班（塔利）。将继续与当地学校的学生和教师开展海洋学项目（麦克唐纳）。海洋建模和耦合气候模型的使用将在SFSU（McClean）的教师研讨会上介绍。