OCEAN CURRENTS,
THEIR CAUSES AND EFFECTS SIMPLIFIED.
“Ocean
currents are the general movements of water in the ocean in a fairly defined
direction”
These
ocean currents produced due to the movement of the water not only affect the
71% water portion of earth but also the continental landmasses. Hence their study
is vital for understanding the weather and climate of each part of the Planet.
Like
atmospheric circulation above it the movement of ocean is also responsible for
transfer of heat from tropics to poles.13% of heat from low to high latitude and
25% of heat from tropics to poles is transferred through ocean currents. It is
through the movement of water in large currents that ocean play vital role in
the constant adjusting the heat Imbalance of earth’s surface. The currents may
b horizontal, vertical or diagonal but all the heat carrying activity takes
place in the uppermost 100m (330ft) of water of horizontal currents.
It
is very difficult to distinguish the currents from their surrounding as they
more slowly and steadily, averaging only about 8km/hr. That is why these are
also called (Drifts) as they slowly move in the same direction in which winds
blow the fast moving currents are only observed where narrow straits are
located e.g. between Florida and Cuba.
TYPES OF
CURRENTS
WARM
CURRENTS
The
Currents that move from hotter region towards cold regions.
Examples
North
Equatorial Currents
South
Equatorial Currents
East
Australian Current
COLD CURRENTS
The
Currents that move from cold region towards hotter region.
Examples
East
Greenland Current
Falkland
Current
Kamchatka
Current
CAUSES, ORIGIN
AND GENERATION OF OCEAN CURRENTS
The
ocean currents are produced in several ways
PREVAILING WINDS
The
blowing winds provide the kinetic energy to the water that enables it to drift
in the direction of the winds.
EVAPORATION
High
rate of evaporation causes lowering of water level due to the escape of water
molecules, as a result the water from surrounding areas of low evaporation move
towards the areas of higher evaporation. For instance the Mediterranean Sea has
higher evaporation rate as compared to the Atlantic Ocean, so the current moves
from Atlantic Ocean towards Mediterranean Sea to compensate evaporation losses.
DIFFERENCE OF
TEMPERATURE
It
is property of water that it becomes dense as temperature decreases and the
density is maximum at 4⁰C. Due to
increase in the density the water becomes heavier and settles down that result
in a net influx of water from tropics towards poles is created in the form of
water Current.
SALINITY
DIFFERENCE
The
increase in salinity result in the increase of water density, hence the water
of more saline oceans settle down and the water from surrounding less saline
areas move towards it in form of water Current.
ROTATION OF THE
EARTH
The
earth is constantly rotating around its axis as a result Coridis Force is
produced. This force acts on the water bodies and moves them in specific directions.
A good example of this effect is the Zigzag path of the rivers under influence
of these forces.
SHAPE OF THE COASTS
The
coastal shapes not only change the direction of the currents but also have the
ability to generate the currents. The shape of the coast may be such that the
water is piled up producing a slightly higher sea level as compared to the
surrounding Ocean. As a result Ocean Current may be generated. It is due to the
shape of the coast that the North Equatorial Current is diverted towards
North-East on reaching gulf of Mexico and comes out as Gulf Stream.
CHANGE OF
SEASONS
Sometimes
the change in seasons acts as driving force for current generation. A good
example is in North Indian Ocean. Here South-West Monsoon Drift and North-East
Monsoon drift are the currents that are governed by Monsoon winds that move
from East to West in Summer and from West to East in the winter season.
EFFECTS OF THE
OCEAN CURRENTS
EFFECT ON
CLIMATE
The
currents influence the Temperature, Rainfall and many other Climatic elements
of a particular area.
TEMPERATURE
When
we look at the Map, New-Foundland and United Kingdom are almost on the same
Latitude but New-Foundland remain frozen for almost 9 months due to the cold
Labrador Current flowing near it whereas ports of United Kingdom are open
almost the whole year.
RAINFALL
The
winds that flow over the warm currents have the ability to carry large amount
of water so they cause heavy rainfall on condensation. The winds that blow over
the cold currents do not have this ability so they don’t produce rainfall. It
is interesting to note that most of the hot deserts have cold currents in their
neighborhood. For instance Canaries Current flow along the Sahara Desert and
the Bengulla Current along the Kalahari Desert.
FOG
Thick
fogs are produced at the meeting points of the cold and warm Ocean Currents
e.g. at New-Foundland thick fog occurs due to the meeting of warm Gulf Stream
and cold Labradore Current.
EFFECT ON TRADE
EFFECT ON
AVAILIBILITY OF COASTS
The
coasts along the warm Currents are open almost throughout the year e.g. Ports
of North-west Europe are open whole year due to warm Gulf Stream whereas most
of the parts of eastern borders of North America remain closed for nine months
due to cold Currents.
DANGER TO SHIPS
Cold
currents flowing from poles bring large icebergs that cause accidents. The
point where two currents meet produce fog resulting in accidents.
EFFECT ON MARINE
ORGANISMS
Cold currents bring large quantity of
planktons and provide food for the fish and also serve as good fishing grounds.
Good quality of fish floats to the coasts along the currents. Currents sweep
large quantity of refuge off the coast that serve as food for planktons. Fishing
grounds are produced at meeting points of cold and warm currents.