Along-isopycnal Salinity Variability: Deducing Horizontal Stirring in the Global Ocean from Argo

概述：扩散沿着密度表面是一个重要的因素，在确定海洋中的示踪剂的分布。扩散是由涡旋场决定的，各种大小的涡旋在海洋中水平搅动示踪剂。水平搅拌的一个特征是温度和盐度沿沿着密度面的波动，这是一种经常观察到但分析不足的示踪物。最近的细尺度观测表明，这些沿密度表面的波动被组织成升高的波动区域，这些区域在时间上持续了几年;这表明，涡动搅拌的基本过程在地理上是不同的，在时间上是稳定的，通过调查全球范围内的温度和盐度波动可以获得很多。智力上的优点：该项目将利用Argo浮标数据调查沿被称为等密度线的沿着密度面的盐度变化。 将对近全球海洋从表层到1 000 - 2 000米深度的混合长度和水平扩散率进行估计，并对影响水平扩散的过程进行评估。沿等密度线盐度波动的方差将与平均盐度的水平梯度和垂直梯度进行比较。与水平梯度的相关性，特别是表明，梯度搅拌是最重要的混合长度框架是一个有效的方法来估计水平扩散。在近全球海洋，水平扩散率将使用卫星测高得出的混合长度和速度波动，以及混合层、西部边界流区和近1 000米深度（后者利用阿尔戈浮标漂移得出的速度波动）的额外估计来估计。沿等密度线的盐度波动、混合长度和水平扩散率的地理变化将显示水平搅拌如何随位置、深度、平均速度和示踪剂场以及海洋的其他相关特征而变化。更广泛的影响：这项研究的结果将直接提高我们对示踪剂分布、海洋环流和地球气候的理解。混合长度和水平扩散率的深度结构将提供一个观测估计，涡动搅拌如何随深度变化，可以与建模研究进行比较，并用于改善其参数化的数值模式。评估哪些过程主要控制示踪剂波动的演变，将允许其他当前或未来的水平扩散估计的方法进行评估，特别是估计低于海洋表面。在这项研究中使用的方法可以推广到未来，包括其他示踪剂的额外信息。该奖项还将支持早期职业海洋学家在她的第一个独立的研究项目。

Overview: Diffusion along density surfaces is a significant factor in determining the distribution of tracers in the ocean. Diffusion is determined by the eddy field with eddies of all sizes horizontally stirring tracers in the ocean. One signature of horizontal stirring is fluctuations of temperature and salinity along density surfaces, a frequently observed but under-analyzed tracer. Recent fine-scale observations show that these along-density surfaces fluctuations are organized into regions of elevated fluctuations that are temporally persistent over several years; this suggests that the underlying processes of eddy stirring are geographically varied and steady in time with much to be gained by investigating temperature and salinity fluctuations on a global scale. Intellectual Merits: This project will use Argo float data to investigate salinity variability along density surfaces known as isopycnals. Mixing length and horizontal diffusivity estimates, as well as an assessment of the processes that influence horizontal diffusion, will be made from the surface to 1000-2000 m depth in the near-global ocean. The variance of along-isopycnal salinity fluctuations will be compared to horizontal and vertical gradients of mean salinity. A correlation with horizontal gradients in particular indicates that the gradient available to stir is of primary importance and a mixing length framework is a valid approach for estimating horizontal diffusivity. In the near global ocean, horizontal diffusivity will be estimated using mixing length and velocity fluctuations derived from satellite altimetry, as well as additional estimates in the mixed layer, western boundary current regions, and near 1000 m depth (the later utilizing velocity fluctuations derived from Argo float drifts). Geographic variations in along-isopycnal salinity fluctuations, mixing length, and horizontal diffusivity will show how horizontal stirring varies with location, depth, mean velocity and tracer fields, and other relevant features of the ocean.Broader Impacts: Results from this study will directly improve our understanding of tracer distributions, ocean circulation, and earth's climate. The depth structure of mixing length and horizontal diffusivity will provide an observational estimate of how eddy stirring changes with depth that can be compared against modeling studies, and used to improve their parameterization in numerical models. An assessment of which processes predominantly control the evolution of tracer fluctuations will allow the methods of other current or future horizontal diffusivity estimates to be evaluated, especially estimates below the ocean surface. The methods utilized in this study can be generalized in the future to include additional information from other tracers. This award will also support an early career oceanographer in her first independent research project.