The simple relationship between the direction of the wind and the direction of the Ekman layer transport in the deep ocean is valid as long as the total water depth H is larger than the depth of the Ekman layer d E . As stated in the previous chapter, the great advantage of deep ocean dynamics is that detailed knowledge of the current distribution in the Ekman layer is not essential to describe its role in the ocean circulation. This is no longer true in the shallow water situation, which requires an analysis of the vertical velocity profile. The first topic of this chapter is therefore a description of the Ekman layer structure. Figure 3.1 shows how current speed and direction change with depth in an Ekman layer generated by a wind blowing over a deep ocean.
Current speed is largest at the surface and decreases rapidly with depth.
This depth is therefore taken as the bottom of the Ekman layer or Ekman layer thickness d E . Somewhere further down in the water column the current flows at right angle to the wind, while below that depth it flows at various angles against the wind direction. The total transport in the Ekman layer is the combined effect of water movement in the Ekman layer, ie the integral from the surface to the depth d E . Only the transport components perpendicular to the wind direction contribute to the final integral. The rather intricate structure of the Ekman layer is the result of a balance between friction and the Coriolis force .