Notes:
Nansen, in 1898, observed that icebergs moved at angles of between 30-30 degree to the right of the surface winds. He noticed this over many measurements, concluding that ocean currents were not the explanation. He argued that the balance between three forces exists:
He later asked his colleagues Bjerknes to have a student working on a theoretical study of this problem: Ekman.
Ekman assumed STEADY, HOMOGENEOUS and horizontal flow with friction on a rotating Earth. Hence, the horizontal and time derivatives are zero.
Leaves a balance between vertical friction and the Coriolis force:
Ekman assumed that A_{Z} is a constant throughout the boundary layer. Took following boundary conditions:
These equations are more complex to solve than the inertial equations, but Ekman used complex variables:
The observed instantaneous surface currents can be 30° - 60° to the right of the wind. Maximenko and Niiler found that this angle varies as function of latitude. An explanation for this could be A_{Z} and stratification. Another explanation is related to vertical variations of A_{Z}, which is thought to grow linearly away from the sea surface.
We go back to the balance of Equations (1) and (2), now with following boundary conditions at the surface and deep ocean:
If we vertically integrate these equations between z = 0 and z = -∞:
Last modified: Nov 2014
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