Robert Hallberg
NOAA Geophysical Fluid Dynamics Laboratory

The Physics of the Ocean Boundary Layer and Its Representation in Climate Models


The ocean’s surface boundary layer is critical for modeling the climate system, and can profoundly influence the overall stability and reliability of coupled climate models.  This talk will review the dominant physical processes that govern the dynamics of the ocean boundary layer, and how these processes have traditionally been treated in ocean models. Challenges with using these traditional approaches in global climate models can include excessive complexity, obfuscating degrees of empiricism, significant dependence on model resolution, and poor stability of the coupled ice-ocean-atmosphere system as a whole. The talk will then present a new framework for modeling the dynamics of the ocean boundary layer based on an implicitly integrated turbulent kinetic energy budget. Because this new approach is cast in a form that is emphasizes well-known fundamental physical principles, it facilitates understanding by the broad community of climate model users, even among people with only a basic exposure to college-level physics. The implicit nature of this new approach both allows it to be used in climate models with long timesteps compared with the short timescales over which turbulence evolves, eliminates stability issues in the coupled system, and gives a remarkably weak dependence on a model’s vertical resolution. Finally, it will be shown that this new approach substantially improves key aspects of the ocean boundary layer in GFDL’s new CM4 coupled climate model.

Time and place
Tuesday 14 June 2016, 11.15
Room C609, Arrhenius Laboratory, 6th floor