Internal Waves and Mixing above the South-West Indian Ridge

西南印度山脊(SWIR)是一个缓慢扩展的锯齿状山脊，沿着南极和非洲板块的边缘延伸7700公里。由于正压潮汐和内波的产生，SWIR是经历公海能量损失的最大区域之一。西印度洋次表层洋流的几个主要分支流经西南红外海，并受到湍流混合的影响，这可能对通过该区域的所有水团的循环产生重大影响。最近的证据表明，由于内波引起的湍流混合增加存在于SWIR的整个长度上，然而，科学家需要更好地了解产生升高湍流的动力学过程，以确定这种湍流影响的实际来源。斯克里普斯海洋研究所的海洋学家提出了沿SWIR的小型垂直尺度内波的两个可能来源：从南大洋传播的低模近惯性波在地形上的散射，以及在粗糙的水深测量上由正压潮汐流在当地产生的内潮。该项目的研究人员建议利用一系列创新仪器研究SWIR上方高空混合的规模、空间结构和原因。通过使用一系列数值模拟实验以及舰载多普勒声纳、快速剖面仪CTD和McLane系泊剖面仪的组合，原理调查人员将获得SWIR上几个位置的内波和混合的高分辨率时间序列。这项工作预计将对理解印度洋盆地的昼夜混合作出重大贡献，并为世界各地粗糙地形地区混合的基本动力学提供新的线索，这是一个重要但相对较少研究的物理海洋学主题。除了主要的科学贡献外，拟议的工作还将提供资金，以支持两名职业生涯早期科学家的发展，以及对研究生进行教育和培训，使其参与实地工作和数据分析。

The southwest Indian Ridge (SWIR) is a slow spreading jagged ridge that extends 7700 kilometers along the edge of the Antarctic and African plates. The SWIR is one of the largest areas that experiences open ocean energy loss due to barotropic tides and the generation of internal waves. Several major branches of sub-surface currents in the Western Indian Ocean flow over the SWIR and are subject to turbulent mixing which may have a significant effect on the circulation of all of the water masses that pass through this region. Recent evidence suggests that increased turbulent mixing due to internal waves exists along the entire length of the SWIR, however, scientists need a better understanding of the dynamical processes that produce elevated turbulence to determine the actual source of this turbulent influence. Oceanographers from Scripps Institute of Oceanography propose two probable origins for small vertical-scale internal waves along the SWIR, topographically scattering low-mode near-inertial waves that propagate from the Southern Ocean, and locally generated internal tides produced by barotropic tidal flow over rough bathymetry. The investigators of this project propose to study the magnitude, spatial structure, and causes of elevated mixing above the SWIR utilizing a collection of innovative instrumentation. Through the use of a series of numerical modeling experiments and a combination of shipboard Doppler sonar, a rapid profiling CTD, and McLane moored profilers, the principle investigators will obtain a high resolution time series of internal waves and mixing in several locations over the SWIR. This work is expected to make a significant contribution to understanding diapycnal mixing in the Indian Ocean basin and shed new light on the fundamental dynamics governing mixing in locations of rough topography worldwide, an important and relatively little studied topic physical oceanography. In addition to the primary scientific contributions, the proposed work will provide funding to support the development of two early-career scientists as well as education and training for graduate students to participate in both field work and data analysis.