Sverdrup Transport
- Sverdrup balance assumes the internal flow is geostrophic, a uniform depth of no motion, and the correctness of Ekman transport. However, the actual depth of no motion in the tropics is poorly constrained
- Solutions are limited to the east side of the ocean because $M_x$ grows with $x$; mass conservation is forced by north-south currents in a thin, horizontal boundary layer
- Only one boundary condition can be satisfied, no flow through the eastern boundary. More complete descriptions of the flow require more complete equations
- The solutions do not give the vertical distribution of the current
- Results were based on two cruises plus average wind data; later work with more recent wind data gave better agreement if the level of no motion is 500 m, but results were poorer at other depths
- We do not have sufficient information to test the theory, but noted that Sverdrup’s relationship is so central to theories of ocean circulation that “it is difficult to overestimate its importance.” More recent observations (Yu and McPhaden, 1999) show that in the equatorial Pacific, the flow is in Sverdrup balance.
Streamlines of mass transport in the eastern Pacific calculated from Sverdrup’s theory using mean annual wind stress
Depth-integrated Sverdrup transport applied globally using the wind stress. Sverdrup solutions have been used for describing the global system of surface currents. The solutions are applied throughout each basin all the way to the western limit of the basin. There, conservation of mass is forced by including north-south currents confined to a thin, horizontal boundary layer.