Collaborative Research: Isopycnal Spectra and Stirring on the Submesoscale and Finescale in the Upper Ocean

横向搅动是主要过程之一，沿着平流和底流混合，决定着上层海洋中水团特性、营养物和溶解气体的分布和归宿。海洋大气环流模式可以解决尺度大于30公里的搅拌，区域模式可以解决尺度接近1公里的搅拌，但是由未解决的亚中尺度过程引起的等密度搅拌仍然必须参数化。在亚热带太平洋的新的高分辨率观测将提供深入了解的基本物理学和这些过程如何在上层海洋运作，以改善这种参数化的涡旋解决海洋环流模型。结果也适用于其他旋转分层流体中的亚中尺度，如地球大气、恒星和气体巨星等占据相同的参数空间。一名博士后研究员将接受在海洋中尺度以下这一迅速兴起的领域解释数据的培训。两名研究生将有机会参加航海研究，一阶Rossby数和梯度Richardson数亚惯性流已成为海洋参数空间的一个领域，尚未完全理解，但可以进行观测，建模和理论。由于观测约束的缺乏，在长度尺度上的等密搅拌的运动学和动力学比Rossby变形长度短100公里，比外部湍流尺度长1米，没有一个完善的理论基础。准地转（QG）理论预测，在比罗斯比长度尺度更短的尺度上，示踪剂应该有一个斜率为负一的谱（对应于斜率为正一的示踪剂梯度谱）。这与跨越30米至500公里的水平波长的许多观测结果形成鲜明对比，这些观测结果报告了在这个波数带上显着更红，而且往往几乎是平坦的示踪剂梯度谱。类似的动态比较很少见。将使用拖曳链和紧密间隔的温度、电导率和压力传感器以及船上声学多普勒海流剖面仪对海洋上部150米的高分辨率剖面进行采样。该项目将描述等密度线上被动示踪剂（水团、香料、盐度异常）的水平波数谱，使其水平波数高于先前完成的水平波数，并解决被认为是造成这些尺度上的搅动的亚惯性O（1公里）水平应变张量，以及确定应变时标。这些测量将提供一阶Rossby数和Richardson数流的关键观测约束。

Lateral stirring is among the primary processes, along with advection and diapycnal mixing, that determines the distribution and fate of water-mass properties, nutrients and dissolved gases in the upper ocean. Ocean general circulation models resolve stirring on scales larger than thirty kilometers, and regional models on scales close to one kilometer, but isopycnal stirring by unresolved submesoscale processes must still be parameterized. Novel high-resolution observations in the sub-tropical Pacific Ocean will provide insight into the underlying physics and how these processes operate in the upper ocean in order to improve such parameterizations for eddy-resolving ocean circulation models. Results should be applicable to the submesoscale in other rotating stratified fluids such as the atmosphere of Earth, stars and gas giants that occupy the same parameter space. A post-doctoral fellow will be trained in interpretation of data in the rapidly emerging field of oceanic submesoscales. Two graduate students will have an opportunity to participate in sea-going research.Order one Rossby number and gradient Richardson number sub-inertial flows have emerged as an area of ocean parameter space that is incompletely understood but becoming accessible to observations, modelling and theory. The kinematics and dynamics of isopycnal stirring on length scales shorter than the Rossby deformation length of order 100 kilometer and longer than outer turbulence scales of order one meter do not have a well-established theoretical underpinning because of the paucity of observational constraints. At scales shorter than the Rossby length scale, quasigeostrophic (QG) theory predicts that tracers should have a spectrum of slope of minus one [corresponding to tracer-gradient spectra with slope plus one]. This contrasts with numerous observations spanning the horizontal horizontal wavelengths 30 m to 500 km which report significantly redder and often almost flat tracer-gradient spectra over this wavenumber band. Similar dynamical comparisons are in short supply. High resolution sections of the upper 150 meter of the ocean will be sampled using a towed chain with tightly spaced temperature, conductivity and pressure (CTD) sensors and the shipboard Acoustic Doppler Current Profiler (ADCP). This project will characterize the horizontal wavenumber spectra of passive tracers (water-mass, spice, salinity anomalies) on isopycnals to higher horizontal wavenumbers than previously accomplished, and resolve the sub-inertial O(1 km) horizontal strain tensor thought responsible for stirring on these scales, as well as determine strain timescales. These measurements will provide key observational constraints on order one Rossby number and Richardson number flows.