ICSE Class 9 Answered

The factors that affect ocean currents are:

• Temperature: Temperature affects the origin and nature of ocean currents. As the equator and tropical regions are warm, the oceans lying near the Equator and the tropics are warmer than the oceans lying near the Polar Regions. Thus the ocean currents from warm equatorial regions move towards the Polar Regions as warm currents. Similarly, the cold currents move from the Polar Regions to the Equatorial regions as the cold currents.

   

• Level of Salinity: Oceans with a higher level of salinity are denser than oceans having lower levels of salinity. Generally, ocean currents are generated from areas of less salinity to areas of high salinity. Since the Mediterranean Sea is more saline than the Atlantic Ocean, most of the ocean currents flow from the Mediterranean Sea to the Atlantic Ocean.

   

• The Rotation of the Earth: The Earth rotates from west to the east. The speed of the rotation of the Earth is maximum at the equator, all moving bodies move in a clockwise direction in the Northern Hemisphere and anti clockwise in the Southern Hemisphere. This is also known as the CoriolisEffect.

   

• The Planetary Winds: Winds affect ocean currents. The trade winds blow between the Equator and the Tropics. These winds thus move the equatorial water towards the Pole. For example, the South east Trade Winds drift the Equatorial Current to the eastern coast of Australia as the warm East Australian Current.

   

• Landforms: A landform may influence ocean currents. For example, the shape of various landmasses may obstruct the flow of water and influence its movement. For example, the South Equatorial Current gets deflected towards the Northern Hemisphere.