Coastal Upwelling In Eastern Boundary Currents

Fas tern boundary currents are less spectacular ihan western boundary currents and have received less attention. Nevertheless, the upwelling w hich is often associated w ah them has biological implications of considerable ecological and economic importance.

In Chapter 3. you saw how the average motion of (he wind-driven layer is 90" non soU- of the wind direction (Figure 3.6(b)). and hence how cyclonic w inds lead to a surface divergence and upwelling in mid-ocean ¬°Figure 3.24(a) and (b)). Coastal upwelling is the result of a divergence of surface water aw ay from the coastal boundary.

In which direction must the wind blow in order to cause most upwelling.'

Because Fkman transport is 90- mm sole of the w ind direction, the most offshore (ransport ol surface waier. and the most upwelling. occurs in response to hm^shfrc vqitulnnviinl winds, not offshore winds.

The situation is complicated by the fact that the offshore movement of surface water leads to a lowering of sea-level towards the coast. This results in a landward horizontal pressure gradient, which in turn generates geographic flow towards the Equator Phe equator ward geos trophic current, combined with the offshore wind-driven current, results in a surf ace current directed offshore and towards the Equator How this arises is explained in detail in Figure 4.36 and its caption, which you should study carefully.

Ekman transport surface transport

Ekman transport surface transport

Ekman transport current because of, resultant surface gradient in tranzón sea-surface, '

Was this article helpful?

0 0

Post a comment