Transcript Ocean Currents

Ocean Currents
Ocean Currents



An ocean current is a large amount of
ocean water that moves in a particular
unchanging direction.
There are more than 20 major ocean
currents.
Currents can be warm or cold,
depending on their origin.
Two types of ocean currents
1.
2.
surface currents (extend to an average
depth of 200m).
Thermohaline currents (occur deeper
than 200m).
Surface Currents

1.
2.
3.
These are caused by:
wind action
the Earth’s spin (Coriolis Effect)
shape of the continents
Wind Action

As air moves over the ocean’s surface, its
energy is transferred by friction to the
water molecules, causing the ocean water
to move.

Winds travel in a clockwise direction north
of the equator and in a counter-clockwise
direction south of the equator. Currents
travel in the same direction
Earth’s spin (Coriolis Effect)


Earth spins from west to east (counterclockwise), as winds and currents move over this
spinning body, their paths get re-directed
depending on what side of the equator they are
on.
As a result, air currents flow in a clockwise
pattern in the northern hemisphere and a counterclockwise pattern in the southern hemisphere.
Shape of Continents

Moving currents are forced to turn when
they meet a solid surface.
Deep Ocean Currents

1.
2.
These are caused by:
Temperature
Salinity of the water
Temperature

1.
2.
3.
Water temperature varies with depth.
There are three layers:
the surface – warmest layer
the thermocline – the water temperature
may drop from 20ºC to 5ºC
deep water – temperatures are close to the
freezing point



Temperature affects the density of ocean water.
Cold water is more dense than warm water and
tends to sink.
Temperature differences in water may cause
vertical convection currents where warmer water
is rising and colder water is sinking.
Theses masses of cold water are called density
currents.
Salinity of Water

Density currents can also be caused by
differences in salinity (amount of salt).

Water with a high salinity is denser than
water with a lower salinity.
Local Currents
Local ocean currents include:
i) Labrador current (cold)
ii) Gulf Stream (warm)



Newfoundland and Labrador has a cold
ocean current flowing down from the north
(the Labrador current) and a warm ocean
current flowing up from the south (the Gulf
Stream).
The mixing of these two currents generates
heavy fog for our coastline and also makes
an ideal location for nutrients
Answer the following…
1.
2.
3.
4.
What is a current?
Describe and illustrate a convection current.
Explain the importance of currents to the
survival of aquatic organisms.
Where are some of the most important fishing
areas in our oceans? What causes these areas to
generate such large numbers of fish?