Figure 19

A series of four schematic diagrams that are arranged as a column of two diagrams on the left, labelled '(a)', to show the effect of cyclonic winds, and a column of two diagrams on the right, labelled '(b)', to show the effect of anticyclonic winds on the ocean.

The two diagrams on the top are supported by a key, located in the top right, that shows the meaning of the arrows presented in these diagrams as follows:

a wide arrow shaded blue is labelled 'Ekman transport',

a wide arrow shaded white and fading into orange at the arrow head end is labelled 'wind',

a narrow blue line arrow is labelled 'surface current'.

The diagram on the top left is labelled 'cyclonic wind' and shows an inner circle of six curved blue line arrows pointing in a counter-clockwise direction, with an outer circle of six curved broad white/orange arrows pointing also in a counter-clockwise direction. There are six straight broad blue arrows located outside the outer circle and pointing in an outward direction, radiating away from the centre of the circle.

The diagram on the top right is labelled 'anticyclonic wind' and shows an inner circle of six curved blue line arrows pointing in a clockwise direction, with an outer circle of six curved broad white/orange arrows pointing also in a clockwise direction. There are six straight broad blue arrows, this time located between the white/orange arrows and the blue line arrows and pointing inwards toward the centre of the circle.

The lower two diagrams show a vertical profile through the upper layer of the ocean.

There are three layers in each diagram.

There is a narrow horizontal blue line in both diagrams that divides the top two layers. This line is labelled in the left diagram only as 'sea surface'.

There is a thick horizontal blue line in both diagrams that divides the bottom two layers but labelled in the right diagram only as 'thermocline'.

The diagram in the lower left shows a sea surface line which is concave and a thermocline line that is convex and a resultant thinner layer between the two in the middle. There are blue arrows pointing from the thermocline up to the sea surface and then horizontally along the underside of the sea surface line. These lines are labelled 'upwelling'.

The diagram in the lower right shows a sea surface line which is convex and a thermocline line that is concave and a resultant thicker layer between the two in the middle. There are blue arrows that point along the sea surface toward the middle and then down to the thermocline. These lines are labelled 'downwelling'.

4.4 Divergence and convergence