Across-Scale Energy Transfer In The Southern Ocean

• Main Author: Ferris, Laur
• Format: Text
• Language: English
• Published: W&M ScholarWorks 2022
• Subjects: Oceanography; Southern Ocean
• Online Access: https://scholarworks.wm.edu/etd/1673281632; https://doi.org/10.25773/v5-enmt-fn19; https://scholarworks.wm.edu/context/etd/article/7356/viewcontent/Ferris_updated.pdf

Numerous physics are responsible for forward energy cascade at oceanic fronts but their roles are not fully clear. This dissertation investigates wind-sheared turbulence in the ocean surface boundary layer (OSBL), internal wave interactions in the ocean interior, and instability-driven turbulence in energetic jets; with attention paid to the parameterizations used to quantify them. At the OSBL, meteorological forcing injects turbulent kinetic energy (TKE), mixing the upper ocean and rapidly transforming its density structure. In the absence of direct observations or capability to resolve sub-grid scale turbulence in ocean models, the community relies on boundary layer scalings (BLS) of shear and convective turbulence to represent this mixing. Despite the importance of near-surface mixing, ubiquitous BLS representations of these processes have been under-assessed in high energy forcing regimes such as the Southern Ocean. Glider microstructure from AUSSOM (Autonomous Sampling of Southern Ocean Mixing), a long-duration glider mission, is leveraged to show BLS of shear turbulence exhibits a consistent bias in estimating TKE dissipation rates in the OSBL. In the interior, finescale strain parameterization (FSP) of the TKE dissipation rate has become a widely used method for observing mixing, solving a coverage problem where only CTD profiles are available. However there are limitations in its application to intense frontal regions where adjacent warm/salty and cold/fresh waters create double diffusive instability. Direct turbulence measurements from DIMES (Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean) and AUSSOM are used to show FSP can have biases of up to 8 orders of magnitude below the mixed layer when physics associated with T/S fronts are present. FSP often fails to produce reliable results in frontal zones where temperature-salinity (T/S) intrusive features contaminate the CTD strain spectrum, as well as where the aspect ratio of the internal wave spectrum is known to vary greatly with depth ...