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具有多种作用，包括印度尼西亚贯流水的吞吐量和转化、来自大西洋和南大洋的深水和底层水的上升流，以及由这种上升流提供的深水、中层水和温跃层水的扩散生产。南印度洋通风和上层海洋倾覆的年代际变化已经被证明。该项目旨在：(1)改进对印度洋翻转环流和昼夜混合的估计，以及相关的碳和营养预算。现代的、全面的数据分析和高分辨率的GCM将被用来解释和缩小当前估计的广泛范围。(2)描述受复杂的盆地几何形状和强迫的影响，混合和翻转的区域(面向盆地、东西方向、赤道)的分布，确定这些不均匀如何影响碳、人为碳、氧、淡水和热量输送和散度。(3)分析从1987年到2009年S 32°翻转环流的变化。计算了2009年春季32°S断面的质量、热量、淡水、二氧化碳、氧气和营养物质收支，与以往的工作进行了比较，并根据风和浮力强迫的变化(包括南环状模式)进行了分析。三种互补的方法将用于估计全流域的环流、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WOCE/JGOFS断面和32S重复断面1987、2002、1995和2009年的化学和物理资料进行了分析；(3)对最近使用示踪剂的高分辨率POP模式中的翻转和昼夜混合进行了分析。该项目将包括对平均环流和季节性(季风)环流的分析。碳传输将与之前基于观测的结果和OCMIP模型的结果进行比较。智力上的优点：拟议的工作是独特的，因为它将侧重于印度洋昼夜过程的地理分布，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：适用于大范围、频繁采样的状态估计；适用于详细编制财产预算的全化学高分辨率天气断面分析；以及适用于研究动力过程的使用观测强迫的高分辨率OGCM结果。该项目将首次使用WOCE/JGOFS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排出的位置和大小联系起来，从而将源/汇区域与翻转和混合中的不对称联系起来。该项目还将通过对2009年32S重复水文剖面的分析来研究南印度的年代际变化，该剖面是由美国重复水文/二氧化碳计划收集的，该计划本身并不为分析提供资金。广泛的影响：对海洋二氧化碳吸收的估计对于准确预测未来大气中的二氧化碳含量是必要的；对无机碳通量差异的直接估计将限制通过地表二氧化碳测量和数值模型所作的估计。已经证实了亚热带印度洋的通风和翻转变化，该项目将把十年时间序列延长到2009年。研究生将得到资助(SIO)。将为25名中学教师举办关于海洋环流和气候变化的讲习班(塔利)。将继续与当地学校的学生和教师一起开展海洋学项目(麦克唐纳)。海洋模型和在耦合气候模型中的使用将在旧金山州立大学(McClean)的教师研讨会上介绍。

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).