Propagation of the near-inertial energy and the role of eddies in the ocean.

• Main Author: Zhai, Xiaoming.
• Other Authors: Ph.D.
• Format: Text
• Language: English
• Published: Dalhousie University 2014
• Subjects: Physical Oceanography; Canada; North Atlantic; Northwest Atlantic
• Online Access: http://hdl.handle.net/10222/54976

In this thesis, we find that (1) the wind power input is reduced by about 17% when ocean surface currents are included in the wind stress parameterization in a high-resolution model of the northwest Atlantic Ocean; (2) contrary to the traditional view that wind-induced near-inertial energy is redistributed by the beta-dispersion effect, we argue that the bulk of energy input from the wind to the near-inertial frequency band is dissipated, and leads to mixing, locally within mesoscale eddies in the ocean rather than being spread equatorward by beta-dispersion. Therefore, strong diapycnal mixing associated with near-inertial wave breaking is expected to occur in the Gulf Stream system and other regions of the world ocean with high levels of eddy kinetic energy; (3) eddy-induced mixing in the surface mixed layer due to interaction with the atmosphere can play an important role in the ocean heat budget. We then estimate the eddy-induced diffusivity for heat in the surface mixed layer in two ways: (i) directly combining satellite-derived geostrophic velocity and sea surface temperature anomalies from the western North Atlantic Ocean and (ii) conducting numerical experiments with a high-resolution model of the northwest Atlantic Ocean. The surface eddy-induced diffusivities estimated from these two methods are broadly consistent with each other and show considerable spatial variability with large values to the south of the Gulf Stream and smaller values within the Gulf Stream itself. Finally, we introduce a new method (the semi-diagnostic method) for use with ocean models, which has the advantage that model drift is effectively prevented, while at the same time the meso-scale eddy field is free to evolve. This new method is then used to probe the importance of the eddy-driven circulation in the northwest Atlantic Ocean, and we find that the eddies strongly reinforce the eastward Gulf Stream jet and the northern recirculation in the slope region, with over 50% of the total transport of this recirculation being directly eddy-driven. The counterpart of the semi-diagnostic method is also used to examine the impact of assimilating eddies on the large-scale circulation. Thesis (Ph.D.)--Dalhousie University (Canada), 2007.