Numerical and Observational Evidence
169
Fig. 3.11.5. Potential vorticity on the ao = 26.25 - 26.75 surface in the Pacific ocean. (From Keffer
1985)
may be shielded from direct Ekman pumping over most of their horizontal
extent. Are these driven by potential vorticity homogenization or by sources of
potential vorticity in the zone where they outcrop, or by some combination of
both?
Quasi-geostrophic theory is unable to deal with this issue, and the next
chapter takes up the question of the dynamics of density layers and interfaces
which suffer such large changes in depth that quasi-geostrophic theory is no
longer accurate, and whose outcropping introduces an entirely new mechanism
to set deeper layers into motion, namely, ventilation of the thermocline by the
surface layer of the ocean.
References
Anderson, D.L.T. and Gill A. E., 1975: Spin-up of a stratified ocean, with application to upwelling.
Deep Sea Res., 22, 593- 596.
Batchelor, G.K. 1956: On steady laminar flow with closed streamlines at large Reynolds numbers.
J. Fluid Mech ., 1, 177- 190.