| The key purpose of this thesis is to analyze the role of surface buoyancy anomalies and mean gradients in ocean dynamics. The sea surface influences ocean dynamics through heat fluxes and wind stresses. The quasi-geostrophic (QG) framework services as a dynamical basis to describe the linearized evolution of potential vorticity and the ocean surface buoyancy. The increasingly high temporal and spatial resolution surface observation from satellite measurements suggests the surface dynamics to be closely related to the part of QG dynamics that is entirely controlled by surface buoyancy fields. Here, using both analytical derivations and numerical simulations, we integrate surface dynamics with classic QG theories to improve our understanding of the observed ocean surface.;First, we investigate the effects of surface buoyancy gradients on oceanic Rossby wave propagation. We give a new way to understand the discrepancy between the observed Rossby wave speed and the speed derived from the classic QG relations. Namely, we provide evidence that, in most cases, sea surface buoyancy gradients speed up Rossby waves, both analytically and numerically.;Second, we compare and develop methods to reconstruct three dimensional ocean motions from two dimensional surface measurements. We include both high resolution sea surface height and sea surface temperature measurements, and instantaneously infer subsurface dynamics under QG framework. We test our methods using output from both QG and primitive-equation simulations.;Third, we readdress the question of connections between ocean vertical motions and sea surface observations from satellite altimetry. Using a high resolution simulation of the globe, we find that surface signals are associated with surface-trapped vertical motions that are largely connected with surface buoyancy fields.;Last, we study the mechanism of energy exchange between surface fields and interior fields in turbulent system under QG framework in the presence of lateral surface buoyancy gradients. By performing a set of simulations with energy initialized in a narrow range of wavenumbers at the surface, we show that, under an unambiguous separation of the surface energy from the total energy, the interior potential vorticity gradient acts as a catalyst in the conversion of surface energy to interior energy. |
