Synthesis of Internal Wave and Turbulence Observations Across the Antarctic Circumpolar Current

Lead PI: Andreas M. Thurnherr

Unit Affiliation: Ocean and Climate Physics, Lamont-Doherty Earth Observatory (LDEO)

September 2017 - August 2019
Project Type: Research

DESCRIPTION: This project uses a new method to reanalyze and synthesize internal-wave and turbulence data already collected from different areas of the Antarctic Circumpolar Current (ACC) region. The research will determine the main patterns of small scale flow (i.e., internal waves, turbulence and mixing) in the ocean and how these differ from location to location. These processes are important because they control the behavior of the Antarctic Circumpolar Current, which in turn affects global ocean circulation. ACC provides a direct connection between the Pacific, Atlantic and Indian Oceans and affects the transport of water, heat, salt, nutrients and other material from the surface to the deep ocean (global overturning circulation). This reanalysis, based on a new method, will reveal common flow characteristics and identify differences that are attributed to the environment itself. The results of such analysis is very valuable in improving our understanding of ocean circulation in the Southern Ocean and it will have significant and broad application on our understanding of ocean circulation and fine scale processes. This study will provide the US oceanographic community with a tested method and software for deriving turbulence parameters from observations thus advancing science but also improve our knowledge on how the oceans operate benefiting society. The analysis focuses on a large amount of oceanographic data, mainly Lowered Acoustic Doppler Current Profiler (LADCP) and CTD profiles, that have been collected in the ACC region during the last decade or so in the context of multiple projects. Prior analyses of fine and microstructure data have been primarily project-specific, and have emphasized regional dynamical processes. While these analyses reveal some common observations, including dependence of turbulence on topographic roughness and near-bottom currents, there are also inconsistencies, regarding the relationship between internal-wave energy and turbulence levels. In this study, a new, bias-free fine structure parameterization method will be used to estimate turbulence disSchool of International and Public Relationstion. This new method is based on Vertical Kinetic Energy (VKE) estimates derived from LADCP/CTD profiles. The project will provide context for some of the existing process studies that are difficult to compare. The turbulence and mixing coefficients that will be estimated, as part of this project, are the first step toward the development of a climatology of turbulence and mixing for the Southern Ocean. These coefficients, which are expected to be useful in many different scientific contexts, will be made publicly available. Improvements to the VKE methodology/software implemented in the context of this project will become part of the public reference implementation and available for use by other scientists.