Ocean currents

The planet's giant 'heating system'

Ocean water never stands still — it flows around the whole world like giant rivers! Red currents carry warm water from the equator to the poles, blue currents carry cold water back. The Gulf Stream warms Europe — that's why London has milder winters than Tashkent, even though it's further north! One drop of water takes 1,000 years to travel around the world.

Ocean currents come in two kinds: surface currents (driven by wind and the Coriolis force — giant gyres, clockwise in the North Atlantic, anticlockwise in the South) and the deep thermohaline circulation (driven by density differences). The Gulf Stream carries 100 million m³ per second — 100 times all rivers — and warms Europe by 5–10 °C. The 'global conveyor belt': cold salty water sinks in the North Atlantic and takes 1,000 years to circle the world ocean. The Antarctic Circumpolar Current is the most powerful. El Niño/La Niña are shifts in Pacific currents that disrupt weather worldwide. Currents carry heat, oxygen, nutrients and plastic (the Great Pacific Garbage Patch). Melting ice may slow the Atlantic conveyor (AMOC) — a climate risk.

Fun facts

• In 1992, 28,000 rubber ducks fell off a ship — the currents carried them around the world and helped scientists map the currents!
• The Gulf Stream carries 100 times more water than all the world's rivers.
• A drop of water takes 1,000 years to travel around the world ocean.