OCEAN CURRENTS
WHAT ARE OCEAN CURRENTS?
- The horizontal movement of a mass of water in a defined direction across distances.
- Ocean water moves horizontally and vertically.
- Horizontal movements are known as currents.
- Whereas vertical changes are called as upwelling or downwelling.
WHAT IS GYRE, DRIFT AND STREAM?
GYRE
- Large rotating ocean currents involved with large wind movements.
- They are caused by the Coriolis force.
DRIFT
- When ocean water moves forward under the influence of winds.
- The term drift may also use to refer to the speed of current.
- E.g. North Atlantic Drift.
STREAM
- It is formed when ocean water moves in a particular route.
- They travel faster than drifts.
- E.g. Gulf Stream.
WHAT ARE THE FORCES RESPONSIBLE FOR OCEAN CURRENTS?
They are influenced by two forces:
Primary forces
- Heating by Sun:
- These cause the water to expand.
- The ocean water near the equator is higher than the middle latitudes.
- Wind:
- Wind blowing on the surface causes the water to move.
- Friction between both affects the movement of the water body.
- Gravity:
- Gravity tends to pull the water down and create variations.
- Coriolis force:
- This causes the water to move to the right in the northern and to the left in the southern hemisphere.
Secondary forces:
- Differences in water density:
- It affects vertical mobility of ocean currents.
- Water with high salinity is denser than low salinity water.
- Cold water is denser than warm water.
- Temperature of water:
- Cold currents occur when the cold water at the poles sinks.
- Warm currents flow towards the poles to replace the sinking cold water.