Circulation: Warm and Cold Currents – Geography – UGC NET Notes

• Ocean currents are the continuous, predictable, directional movement of seawater. It is a massive movement of ocean water that is caused and influenced by various forces. They are like river flows in oceans.
• Ocean water moves in two directions: horizontally and vertically.
  • Horizontal movements are referred to as currents, while vertical changes are called upwellings or downwellings.
• Ocean currents impact humankind and the biosphere due to their influence on climate.

Types of Ocean Currents

Based on Depth

• The ocean currents may be classified based on their depth as surface currents and deep water currents:
  1. surface currents constitute about 10 percent of all the water in the ocean, these waters are the upper 400 m of the ocean;
  2. deep water currents make up the other 90 percent of the ocean water. These waters move around the ocean basins due to variations in density and gravity.
     • The density difference is a function of different temperatures and salinity
     • These deep waters sink into the deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase.