Internally generated circulation and variability in the tropical Atlantic Ocean
The thesis investigates different dynamical and statistical aspects of the Atlantic Equatorial Deep Jets (EDJ) and the central Atlantic Equatorial Intermediate Current System (EICS). One of these is the maintenance mechanism of the EDJ and the central EICS. It is shown that the convergence of the meridional flux of intraseasonal zonal momentum that is associated with the deformation of intraseasonal waves by the equatorial currents can maintain them against dissipation in an idealised ocean model of the tropical Atlantic. Another point that is investigated is the energy transfer between the EDJ and the central EICS. It is shown that the interannually varying EDJ nonlinearly transfer energy to the time mean currents at intermediate depth, strenghtening the central EICS in the western part of the basin and weakening or reversing it in the eastern basin. In addition, a new comprehensive analysis of the spatial and temporal scales of the Atlantic EDJ from Argo float observations is presented, which adds significantly to the available knowledge about the appearance of the Atlantic EDJ in the real ocean. Furthermore, the origin of the enhanced meridional width of the EDJ compared to their theoretically expected width is investigated in a series of idealised ocean models. It is shown that instantaneous meridional widening of the EDJ due to stronger mixing of momentum than of tracers plays a larger role than averaging over intraseasonal meandering of the EDJ.