Ocean Circulation


Ocean circulation is the vast water motion inside ocean basins; the Sun, wind, Earth’s rotation, tides, and water density discrepancies affect those currents. While land and atmosphere take in part of the Sun’s heat, the ocean takes in the majority of that heat. The energy from sunlight makes water expand, resulting in repetitive water’s evaporation and increase of both humidity and temperature; this affects nearby air and leads to rain and storms.

Wind causes surface currents, which move lukewarm surface water towards the poles from the tropical zones; this is known as the Ekman Layer. These currents create huge circular patterns referred to as gyres. In winter, water cools further at the poles and falls towards the ocean depths; the warm water rises to the ocean’s surface and moves back to the tropics and the cycle restarts. This cycle is known as upwelling and downwelling;  it affects the ocean’s chemical, biological, and physical attributes, and the weather in general.

Due to the Earth’s movement, gyres reroute rightwards in the Northern Hemisphere and leftwards in the Southern Hemisphere; this rerouting is known as the “Coriolis force”. This causes sea level rise and fall, which are directly proportional to surface current speed. Saltiness, temperature, and depth have an effect on water density; the colder and saltier the water, the denser it is. Circulation due to density is known as thermohaline, which along with wind circulation forms the Great Ocean Conveyor Belt.

Thermohaline produces North Atlantic Deep Water, where warm dense water reaches the northern North Atlantic where it is cold. The salty water descends; it overflows the mountain chains from Greenland to Iceland to spread in the form of salty water bulk into the oceans. Furthermore, along Antarctica’s borders, highly dense water is present. This water sinks like thin sheets along the continental slope to the ocean’s depth creating Antarctic bottom water, which spreads across many of the oceans’ floor.


Ocean currents and circulation are measured by satellites, using Lagrangian measurements, named after mathematician Joseph Louis Lagrange (1736–1813).  Using Eulerian measurements, named after Swiss mathematician Leonhard Euler (1707–1783), by placing a device in a fixed location and then calculating the current’s speed passing by it or indirectly measuring other criteria that then enables calculating the speed and direction of currents.

Ocean surface currents affect regional climate as they move heat from one place to another through sunlight, which heats water at the Equator more than at higher latitude polar regions. Thus, surface currents carry heat to higher latitudes, which makes them warmer; these currents may form eddies with their flow.

Currents are paramount for marine life as they carry marine creatures worldwide and influence ecosystems. Moreover, these currents may be used in marine power generation, which is acquired by utilizing marine currents’ kinetic energy, as that of the Gulf Stream to produce electric energy. Florida, Hawaii, and Japan are top candidates for a trial; however, this is not a highly adopted method now.


About Us

SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
Continue reading

Contact Us

P.O. Box 138, Chatby 21526, Alexandria, EGYPT
Tel.: +(203) 4839999
Ext.: 1737–1781

Become a member

© 2021 | Bibliotheca Alexandrina