All dynamical processes in the ocean are originally driven (directly or indirectly) by atmospheric processes. However, the ocean is also responsible for a considerable part of the heating and cooling of the atmosphere, in turn leading to atmospheric patterns that may in again influence the ocean. Therefore, the ocean and the atmosphere form a coupled dynamic system that drives for the majority of the meteorological and climatic phenomena that we experience.
Figure 3.1: Highly idealised depiction of the global circulation on Earth (reproduced from Wikipedia.org, http://en.wikipedia.org/wiki/File:Earth_Global_Circulation.jpg)
The quasi-spherical shape of planet Earth combined with the limited inclination of its rotation axis to the plane of its orbit leads to the tropical regions receiving more heat per square meter than the polar regions. The atmosphere responds to this differential heating by trying to equilibrate this imbalance across latitudes through the so-called atmospheric circulation. This atmospheric circulation consists of large-scale displacements of air all over the globe, or winds. In a non-rotating Earth, these winds would be predominantly meridional (north-south or south-north). However, because the Earth rotates, any moving object experiences an additional force directed to the right (resp. left) of its direction in the northern (resp. southern) hemisphere, the so-called Coriolis force. This effect bends the north-south winds so that the atmospheric circulation results in a series of latitudinal belts characterized by specific typical conditions and wind patterns (Figure 3.1).
Of course, the description provided here is greatly simplified, and in practice the atmospheric circulation is also influenced by the presence or absence of continental land masses, mountain ridges, oceans, and of course by seasonal variations in the Earth’s inclination and in its distance to the Sun. However, the main features of this idealized picture can be found back in the large-scale circulation patterns.
