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Graphic: An Encyclopaedia of New Zealand 1966.

Warning

This information was published in 1966 in An Encyclopaedia of New Zealand, edited by A. H. McLintock. It has not been corrected and will not be updated.

Up-to-date information can be found elsewhere in Te Ara.

OCEAN CURRENTS AROUND NEW ZEALAND

Contents


The Formation of Ocean Currents

When the wind blows persistently in a particular direction, the wind stress on the sea surface causes the water in the upper layer to move bodily and a current is thereby formed. These wind-induced currents may be permanent in regions of strong prevailing winds but they do not flow in the same direction as the wind. In the Northern Hemisphere they are deflected to the right of the wind direction and in the Southern Hemisphere to the left by an angle varying between 30 and 60 degrees. This deflection is an effect of the earth's rotation.

The density of sea water depends both upon its temperature and upon its salinity and, since these vary from place to place, the density also varies and gives rise to currents. These density currents are not independent of winds, however, because the wind-induced currents themselves alter the density distributions. Similarly, if warm water is driven from low latitudes into higher latitudes it will be cooled, and thus a limit is set on the differences of density which can be attained. The positions of the land masses and the shape and depths of the ocean basins also affect the currents.