Stratification Anomalies in the Ocean Interior

Bailey Avila, University of Massachusetts Dartmouth, Department of Estuarine and Ocean Sciences, New Bedford, MA, United States, Miles A Sundermeyer, School Marine Sci. & Tech., New Bedford, MA, United States, Marie-Pascale Lelong, NorthWest Research Associates, Boulder, CO, United States, Eric L Kunze, U of Washington, Seattle, WA, United States, Jeffrey J Early, NorthWest Research Associates, Redmond, WA, United States and Cimarron J Wortham, University of Washington, Seattle, WA, United States
Internal waves and vortical mode are ubiquitous in the ocean, providing a conduit for energy transfer from tides and wind-driven circulation to fine- and micro-scale turbulence associated with internal-wave breaking and dissipation. Numerical simulations of a Garrett-Munk internal-wave field are used to study the interactions between internal waves and vortical mode, and the generation of turbulent mixing events and semi-permanent finestructure (vortical mode). Regions of reduced stratification are found to occupy between ~5% and 25% of the model domain, depending on the strength of the anomalies. Decomposition of 3-dimensional model fields into linear internal-wave and vortical-mode components shows that both influence stratification, with ~88% of the anomalies due to linear internal waves and ~40% due to vortical mode, the overlap in percentiles representing regions that are a combination of the two. The time evolution of anomalies is examined, from the initial generation to eventual dissipation. Results further describe the preconditions of these regions, including their relation to a subcritical Richardson number and overturning / mixing events as quantified via Thorpe scales and turbulent dissipation rate.