Interactive Earth: Oceanic currents

Sea currents are large movements of sea water. They are cyclical movements that spread over thousands of kilometers. Scientists distinguish two main types of currents:

• Surface circulation (within the first 300 meters of depth)
• Thermohaline circulation or deep currents

Numerous parameters influence these currents:

• Winds (for surface currents)
• The temperature of the water
• The salinity of the water (directly related to its density)
• The ocean floor relief and the shape of the coastline

Oceanic currents play a major role in explaining climates on Earth. Scientists fear that global warming is disrupting these enormous climate regulators. The Gulf Stream (North Atlantic), which explains the temperate climate of Western Europe, is often cited. A slowdown or a complete stop of the Gulf Stream would cause a profound change in the climate of this entire region.

Marine currents also influence the biological cycles of many marine species due to a seasonal supply of plankton. Migratory animals use these "ecological corridors".

Surface currents form large loops on the surface of the globe called oceanic gyres. These are currents that rotate in the same direction as the prevailing winds. It is the Coriolis force (a consequence of terrestrial rotation) that explains that these currents are clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. It is in the center of these gyres that all kinds of floating waste are concentrated after a journey of several thousand kilometers.

Credits: NOAA (National Oceanic and Atmospheric Administration)

Sitography:

• Benjamin Franklin and the Gulf Stream: https://www.nha.org/library/hn/HN-v44n2-gulfstream.htm
• The first map of the Gulf Stream by Benjamin Franklin: https://commons.wikimedia.org/wiki/File:Franklingulfstream.jpg