Ocean currents move heat around the planet and shape the climate of every coastline they touch. They also steer nutrients, larvae, and drifting debris across entire basins.

Field note: the Gulf Stream carries roughly 31 million cubic metres of water per second past Cape Hatteras.

Want to go deeper on how currents are measured, or on what they do to regional weather?

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Ocean Currents, Explained Simply

Ocean Currents: A Simple Explanation

What Is an Ocean Current?

An ocean current is a steady, directed movement of seawater — a river inside the sea, driven by wind at the surface and by differences in temperature and salt deeper down.

How Do Currents Form?

Surface currents start with wind dragging on the water, then bend as the Earth rotates beneath them. Deep currents form where cold, salty water grows dense enough to sink, pulling warmer water in behind it and closing the loop.

Key Features

  • Gyres: basin-wide rotating systems that trap heat, plankton, and, unfortunately, plastic.
  • Thermohaline loop: the slow overturning conveyor that moves water between the surface and the deep ocean.
  • Upwelling: cold, nutrient-rich water rising along coastlines, which is why a handful of narrow shelves produce most of the world's catch.

Why Do They Matter?

Currents redistribute heat, set regional rainfall patterns, and decide where fisheries thrive. Shift one and the weather on a coast 4,000 km away changes with it.

Field note: a drifting buoy released off Newfoundland can reach the Irish coast in about 14 months.