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For convenience, assume the bottom of the sea is flat and located at z=0, the governing equation and its general solution are the same as the surface case. Ekman layer at the bottom of the sea. Boundary conditions Z=0 (bottom of the sea). or. As z - (into the interior). or.
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For convenience, assume the bottom of the sea is flat and located at z=0, the governing equation and its general solution are the same as the surface case. Ekman layer at the bottom of the sea Boundary conditions Z=0 (bottom of the sea) or As z-(into the interior) or
General solution: If z, VE0, i.e., A=0 If z=0, VE=-Vg=B We have Let
Solution For z0,
The direction of the total currents where The near bottom the total current is 45o to the left of the geostrophic current.
Transport at the top of the bottom Ekman layer Assume , the solution can be written as Using the continuity equation
We have Since
Given the integral i.e., The vertical velocity at the top of the bottom boundary layer Ekman pumping at the bottom.
Wind-driven circulation II ●Wind pattern and oceanic gyres ●Sverdrup Relation ●Vorticity Equation
Surface current measurement from ship drift Current measurements are harder to make than T&S The data are much sparse.
Drifting Buoy Data Assembly Center, Miami, Florida Atlantic Oceanographic and Meteorological Laboratory, NOAA
Annual Mean Surface CurrentPacific Ocean, 1995-2003 Drifting Buoy Data Assembly Center, Miami, Florida Atlantic Oceanographic and Meteorological Laboratory, NOAA
Schematic picture of the major surface currents of the world oceans Note the anticyclonic circulation in the subtropics (the subtropical gyres)
Surface winds and oceanic gyres: A more realistic view Note that the North Equatorial Counter Current (NECC) is against the direction of prevailing wind.
Mean surface current tropical Atlantic Ocean Note the North Equatorial Counter Current (NECC)
Sverdrup Relation Consider the following balance in an ocean of depth h of flat bottom , Integrating vertically from –h to 0, we have (neglecting bottom stress and surface height change) (1) (2) where and Differentiating , we have and Using continuity equation , Sverdrup relation we have