Knowledge you can walk. Read the idea below, then step up to the general, across to peers or down to the specific.
Physical
Ocean Currents
Ocean currents are steady flows of seawater, driven mainly by wind and differences in water density, that help shape climate.
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The idea
An ocean current is a continuous, directed movement of seawater. Several forces push it along, including wind, breaking waves, the spin of the Earth, and differences in temperature and saltiness. The shape of coastlines and the depth of the sea floor bend currents and change their strength.
Currents move sideways across the ocean, and some cross whole ocean basins. They also move up and down. Upwelling and downwelling carry nutrients and gases such as carbon dioxide between the surface and the deep ocean. Scientists group currents as warm or cold, and as drifts, currents or streams depending on how fast and how far they move.
Currents carry heat around the planet, so they shape the climate of the places they pass. The Gulf Stream and the North Atlantic Drift make northwest Europe much milder than other places that are just as far north. The largest current, the Antarctic Circumpolar Current, flows all the way around Antarctica and links every ocean basin together.
Check yourself
Question 1 of 2
Which current is the largest in the world's oceans?
Composition
what it's made of
- Surface currents — Flows in the upper ocean, pushed mainly by the wind.
- Deep-water currents — Slow flows far below the surface, driven by differences in seawater density.
- Upwelling and downwelling — Vertical movements that carry nutrients and gases between the surface and the deep.
- Global conveyor belt — The linked system of currents that moves water and heat across the whole planet.
Connection
how it relates
Under Climate Patterns
Change
how and why it evolves
- Past
- Before modern instruments, sailors learned the paths of major currents such as the Gulf Stream from experience and used them to plan voyages.
- Now
- Together, ocean currents form a global conveyor belt that plays a dominant role in setting the climate of many regions.
- Next
- Scientists study whether a warming climate could change the strength of some currents, which could in turn shift regional weather, though the size of any change is still debated.