Long description

Figure 17

A pair of schematic diagrams depicting the Ekman layer and the forces involved in water movement.

Part (a), on the left, shows a square three-dimensional column of water, shaded pale blue, with a darker blue shading at the top of the right face. The three-dimensional perspective of the diagram such that one of the diagonals of the column is aligned with the page surface and the other diagonal is suggested as protruding from the page, therefore presenting a frontal view of two faces of the column.

The top of the column has undulating blue lines, suggesting the water surface.

There is a dashed black line across the column faces with approximately one third of the column below the line.

The dashed line is labelled 'depth of frictional influence, d'.

The volume above the dashed line is labelled 'Ekman layer'.

On the top of the column there is a broad white arrow that is labelled 'wind' and is pointing to the back and right.

There is a blue line that runs vertically through the Ekman layer, from the top of the column to the dashed line.

Radiating from this vertical line are a series of 20 blue arrows, evenly spaced along the length of the vertical line.

The arrow at the top of the vertical line is the longest of the series of arrows and is pointing from the central vertical line, diagonally along the plane of the paper, to the right.

Each successive arrow down the central vertical line is shorter in length than the one above and is rotated slightly clockwise.

Part (b) on the right is the same basic shaped three-dimensional square column. In this diagram only the Ekman layer is shaded blue and the volume under the dashed line is unshaded.

There are three arrows in this diagram:

On the top of the column is a broad arrow shaded pale blue and pointing back and to the right: this arrow is labelled 'wind stress'. On the front left face of the column is a narrower arrow, shaded grey and pointing out the front to the left at an angle of 180° from the wind stress arrow: this arrow is labelled 'Coriolis force'. On the front right face of the column is a broad arrow shaded blue and pointing to the front and left, at an angle of 90° clockwise from the wind stress arrow and 90° counter clockwise from the Coriolis force arrow: this arrow is labelled 'average motion of the Ekman layer'.