Environmental Engineering Reference
In-Depth Information
ected from the edges
of landmasses and mid-ocean ridges, refracted by
the changes in water depth and diffracted as it
passes through gas between continents. Together,
all these factors produce the dynamic tides. In
addition, different kinds of tides interact with
each other along their boundaries, and the results
are exceedingly complex.
The tide wave is also re
fl
The most important currents are the surface cur-
rents, which are partly caused by the great wind
system of the globe. In addition to this, there are
bottom currents as well as currents downward and
currents upwards due to the uprise of warmer
current. There are also local currents due to the
tides or differences in evaporation and salinity.
The water in the equatorial regions becomes hot
and tends to
ow polewards as warm surface
currents, while the colder water from the poles
creeps along as bottom currents to take its place.
The evaporation in the hot regions causes bottom
currents of cold waters to
fl
1.2.3 Current
The geomorphic importance of currents lies in
their role in transporting sediment and less sig-
ni
ow in below and
replace the loss. The major ocean currents of the
world oceans are shown in Fig.
1.22
.
fl
cantly in erosion. Currents associated with
tides can transport and erode sediment where
fl
ned
to estuaries or other enclosed sections of coast
which experience semi-diurnal tides with a high
range. In mesotidal and microtidal regimes, fast
tidal currents are con
ow velocities are high. This is usually con
Cold Currents and Warm Currents
When current is
owing from a warm to a cold
region, it is naturally a warm current, but when it
fl
fl
ows from a cold to a warm region, it is a cold
current. Notice that the terms
'
warm
'
and
'
cold
'
are relative to the temperature of the neighbour-
ing sea water and that a warm current may swing
round and becomes a cold current.
ned to zones of constric-
tion such as around coastal promontories and
within narrow channels between islands.
Basically, the movements of water from one
part of the ocean to another give rise to currents.
Fig. 1.22
Major currents of the world ocean
