| Idealized formulations of the large-scale oceanic and atmospheric circulations are used to describe the heat and momentum transport within the midlatitude upper ocean-trophosphere system and its role in the generation of low-frequency variability.; In chapter 2, a formulation of the large-scale interaction between the troposphere and the wind-driven circulation in an ocean basin describes a feedback between the oceanic circulation and the oceanic temperature mediated by the atmosphere. Although this feedback is negative, the delayed response of the oceanic velocity to the wind-stress can alter the sign, giving rise to oscillations. The period of this oscillations is linearly proportional to the transit time of long Rossby waves across the basin, and thus is of the order of decades.; In chapter 3, the same formulation is used to illustrate possible mechanisms of connection between the decadal variability in two ocean basins. There are three basic kinds of coupling-induced behavior: Phase-locking, in which the two basins oscillate in synchrony, with the narrower basin following the wider basin by a small time-lag; oscillation death, in which a steady solution is reached, even though each ocean basin, when uncoupled, would have sustained oscillations; and chaos, in which the interbasin coupling induces aperiodic fluctuations characterized by variability at centennial, as well as decadal, time-scales.; In chapter 4, a formulation of a channel flow is used to examine the equilibrium dynamics and thermodynamics of the Antarctic Circumpolar Current. The thermal structure depends on both the mechanical and the thermal atmospheric forcing and it is determined by a leading order balance between the meridional tranport by the wind-driven Eulerian mean and that by the adiabatic baroclinic eddies. The air-sea heat flux depends on the meridional residual circulation, which in turn depends on the processes of vertical diffusion, entrainment/detrainment and, in the polar flank, convection. |
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