Collaborative Research: Estimating the Indian Ocean overturn and diapycnal mixing

印度洋在全球翻转环流和碳循环中扮演着多重角色，包括印度尼西亚通流水的通量和转化，大西洋和南大洋深水和底水的上升流，以及这种上升流所供给的深水、中深水和温跃层水的扩散性生产。南印度通风和上层海洋翻转的年代际变化已得到证实。本项目旨在：(1)改进对印度洋翻转环流和底周期混合的估计，以及相关的碳和营养收支。现代、全面的数据分析和高分辨率GCM将用于解释和缩小目前估计的广泛范围。(2)在复杂的盆地几何形状和时空变化强烈的强迫作用下，表征混合和翻转的区域性（盆地导向、东西向、赤道）分布特征；确定这些不均匀性如何影响碳、人为碳、氧、淡水和热的传输和散度。(3)分析1987 - 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、二氧化碳、氧气和营养收支；并根据风和浮力强迫（包括南环模）的变化进行分析。三种互补的方法将用于估计全盆地环流、翻转和混合：(1)分析环流、温度和盐度的两种状态估计（ECCO和相关的高分辨率SOSE）的印度洋部分；(2)利用反演技术对1987年、2002年、1995年和2009年WOCE/JGOFS剖面和32S重复剖面的化学和物理数据进行分析；(3)分析了高分辨率POP模型中的翻转和横冲混合，该模型最近使用了示踪剂。该项目将包括对平均环流和季节环流的分析。碳运输将与以前基于观测的结果和OCMIP模型的结果进行比较。智力优势：这项工作的独特之处在于，它将关注印度洋底冲过程的地理分布，从而阐明主要的物理机制。它将提供三种不同方法的结果的比较和组合：适合于大尺度、频繁采样的状态估计；分析具有完整化学成分的高分辨率天气部分，适合详细的财产预算；高分辨率OGCM结果利用观测强迫，适合研究动力过程。该项目将是第一个使用WOCE/JGOFS油田将海洋环流、翻转和混合的细节与印度洋二氧化碳吸收和排放的位置和规模联系起来的项目，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32S重复水文剖面来研究南印度的年代际变化，该剖面由美国重复水文/二氧化碳项目收集，该项目本身并不为分析提供资金。更广泛的影响：海洋二氧化碳吸收量的估算对于准确预测未来大气二氧化碳含量是必要的；对无机碳通量散度的直接估计将限制通过地表二氧化碳分压测量和数值模式作出的估计。副热带印度洋的通风和翻转变化已经得到证实，本项目将把年代际时间序列延长到2009年。研究生将被支持（SIO）。将为25名中学教师举办海洋环流与气候变化讲习班（Talley）。将继续与当地学校的学生和教师合作开展海洋学项目（麦克唐纳）。海洋模型及其在耦合气候模型中的应用将在旧金山州立大学（McClean）的教师研讨会上发表。

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).