Types of Currents

There are many types of currents such as those driven by salinity, wind, temperature or the Coriolis effect. Two of the most commonly identified are surface currents and deep ocean currents. Surface currents are driven by winds, are fast and make up 10% of the world’s oceans. In the northern hemisphere surface currents develop clockwise spirals that eventually turn into gyres which are, large systems of circulating ocean currents. Some currents across the globe tend to move with the seasons, for example, the current in the north Indian Ocean changes direction with the reversal of seasonal winds known as the monsoons. North and south equatorial currents are affected also by seasonal changes because of the relocation of pressure systems and wind belts. Surface currents develop anti-clockwise spirals in the southern hemisphere. The other types of currents, deep ocean currents, also known as thermohaline circulation or ocean conveyer belts. These currents generally move in the deep ocean and are caused by temperature, the shape of the ocean floor and salinity. Salinity changes occur because saltier water sink and displaces water that is warmer and less dense.They are also slower moving and make up 90% of the world’s oceans and are generally unnoticeable at the ocean surface.