Present ocean circulation
43
Figure 2.10. ‘Multipass image’ (from a satellite) of the sea surface temperature in the Gulf
Stream region in May 1996 (image from http://fermi.jhuapl.edu/avhrr/).
as that in the wind-stress forcing. Such wind-stress changes cause waves that
propagate through the flow field inducing an adjustment of the flow to the new
forcing conditions. Temporal variations can also occur because mean flows are
sensitive to disturbances which leads to instabilities. These instabilities are at
the origin of the formation of meanders and eddies in currents such as the Gulf
Stream (Fig. 2.10). These considerations lead to the following specific questions:
How is the adjustment of an ocean flow when the wind stress is changing?
What type of instabilities of ocean currents exist and what are the physical
mechanisms of destabilization?
In the chapters 7 to 10, these questions are addressed and again an attempt is
made to answer them from principles of geophysical fluid dynamics. To formulate
the problems, basic material on the propagation of free waves in a rotating liquid
is needed and this is introduced in chapter 7. This theory on free waves is then
generalized in chapter 8 to a stratified flow in a midlatitude ocean basin. To study
43
Figure 2.10. ‘Multipass image’ (from a satellite) of the sea surface temperature in the Gulf
Stream region in May 1996 (image from http://fermi.jhuapl.edu/avhrr/).
as that in the wind-stress forcing. Such wind-stress changes cause waves that
propagate through the flow field inducing an adjustment of the flow to the new
forcing conditions. Temporal variations can also occur because mean flows are
sensitive to disturbances which leads to instabilities. These instabilities are at
the origin of the formation of meanders and eddies in currents such as the Gulf
Stream (Fig. 2.10). These considerations lead to the following specific questions:
How is the adjustment of an ocean flow when the wind stress is changing?
What type of instabilities of ocean currents exist and what are the physical
mechanisms of destabilization?
In the chapters 7 to 10, these questions are addressed and again an attempt is
made to answer them from principles of geophysical fluid dynamics. To formulate
the problems, basic material on the propagation of free waves in a rotating liquid
is needed and this is introduced in chapter 7. This theory on free waves is then
generalized in chapter 8 to a stratified flow in a midlatitude ocean basin. To study