Past Event: Oden Institute Seminar

Numerical simulations of the global oceanic internal tide and gravity wave fields

Brian Arbic, Associate Professor, Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI

Abstract

We discuss numerical simulations of oceanic internal gravity waves (IGWs) on a global scale, on US Navy, NASA, and European high performance computing platforms. IGWs are waves that exist on the interfaces between oceanic layers of different densities. IGWs of tidal frequency are known as internal tides. Beyond tidal frequencies, there is a spectrum of IGWs known as the IGW continuum. The rollover and breaking of IGWs controls most of the mixing in the open-ocean beneath the mixed layer. IGWs also impact the speed of sound, and yield a measurable sea surface height (SSH) signal. Therefore IGWs are important for satellite altimetry missions, including the upcoming Surface Water and Ocean Topography (SWOT) mission, and for operational oceanography in general. We describe our work with the US Navy HYbrid Coordinate Ocean Model (HYCOM), in which we pioneered high-resolution global ocean models simultaneously forced by atmospheric fields and the astronomical tidal potential. We also examine newer simulations performed under similar conditions, on NASA supercomputers, with the Massachusetts Institute of Technology general circulation model (MITgcm). Finally, we briefly describe related work done with the European ocean forecasting model, the Nucleus for European Modeling of the Oceans (NEMO). We summarize several papers on comparison of the modeled internal tides and the IGW continuum spectrum to altimetry and observations from moorings. We briefly discuss the generation of the continuum spectrum and the potential implications for a better understanding of ocean mixing.