Chapter 12 - Vorticity in the Ocean
12.4 Important Concepts
- Vorticity strongly constrains ocean dynamics.
- Vorticity due to Earth's rotation is much greater than other sources of
- Taylor and Proudman showed that vertical velocity is impossible in a uniformly
rotating flow. The ocean is rigid in the direction parallel to the rotation
axis. Hence Ekman pumping requires that planetary vorticity vary with latitude.
This explains why Sverdrup and Stommel found that
realistic oceanic circulation, which is driven by Ekman pumping, requires
that f vary with latitude.
- The curl of the wind stress adds relative vorticity to central gyres of
each ocean basin. For steady state circulation in the gyre, the ocean must
lose vorticity in western boundary currents.
- Positive wind stress curl leads to divergent flow in the Ekman layer. The
ocean's interior geostrophic circulation adjusts through a northward mass
- Conservation of absolute vorticity in an ocean with constant density leads
to the conservation of potential vorticity. Thus changes in depth in an ocean
of constant density requires changes of latitude of the current.