Impact of Vertical Mixing Parameterizations on Internal Gravity Wave Spectra in Regional Ocean Models

• Main Authors: Thakur, Ritabrata, Arbic, Brian K., Menemenlis, Dimitris, Momeni, Kayhan, Pan, Yulin, Peltier, W. R., Skitka, Joseph, Alford, Matthew H., Ma, Yuchen
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: GODAE OceanView 2022
• Subjects: internal gravity waves; vertical wavenumber spectra; MITgcm; KPP mixing parameterization; Geological Sciences; Science; Arctic
• Online Access: https://hdl.handle.net/2027.42/174814; https://doi.org/10.1029/2022GL099614

We present improvements in the modeling of the vertical wavenumber spectrum of the internal gravity wave continuum in high‐resolution regional ocean simulations. We focus on model sensitivities to mixing parameters and comparisons to McLane moored profiler observations in a Pacific region near the Hawaiian Ridge, which features strong semidiurnal tidal beams. In these simulations, the modeled continuum exhibits high sensitivity to the background mixing components of the K‐Profile Parameterization (KPP) vertical mixing scheme. Without the KPP background mixing, stronger vertical gradients in velocity are sustained in the simulations and the modeled kinetic energy and shear spectral slopes are significantly closer to the observations. The improved representation of internal wave dynamics in these simulations makes them suitable for improving ocean mixing estimates and for the interpretation of satellite missions such as the Surface Water and Ocean Topography mission.Plain Language SummaryInternal waves (IWs) exist in the ocean interior due to differences in fluid densities. Breaking IWs cause mixing, which has important effects on ocean temperatures and nutrients. Interactions between internal tides generated by tidal flow over bathymetric features and near‐inertial waves generated by wind yield a spectrum of IWs at many frequencies. Here, we compare the IW spectrum in high‐resolution numerical simulations of a region in the North Pacific with observations from moored instruments. We study the effects of the “background” mixing components of the widely used K‐Profile Parameterization (KPP) vertical mixing scheme on the vertical structure of the IW field. The KPP background parameterizes the mixing action of IWs, which is not resolved in coarser‐resolution global ocean models. In our high‐resolution simulations, the IW field is highly active, and the KPP background components turn out to be mostly redundant in this setting. The modeled IW field lies closer to observations when we turn off the KPP background. ...