The effect of depth variation of the Austausch coefficient Av on the vertical velocity profile.
Change of current speed with depth for a constant coefficient Av (red) and for a coefficient Av which decreases exponentially with depth (blue). Absolute speeds and depths are shown as an example but otherwise arbitrary.	Observations of a surface Ekman layer on the Siberian shelf. Cyan circles show observed currents. The green curve is the Ekman spiral determined using a depth-independent Austausch coefficient Av = 0.02 m2 s-1, the magenta curve gives the Ekman spiral for an Austausch coefficient which decreases with a depth dependence of 0.0385 ( (d+0.1) / 22.4 )3/4, where d is the distance from the bottom in meters. White dots indicate depth levels on the current spirals.

(Total water depth in the example from the Siberian shelf was 22 m, so the condition dE2 << H2 was not satisfied. The Ekman spiral should therefore not be compared with Figure 3.1 but with Figure 3.7 which shows that the observed situation corresponds to H = 0.3 dE. This gives dE = 73 m).

Second diagram adapted from Sverdrup et al. (1942), based on Fjeldstad (1929).

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