Ocean currents are massive water flows that redistribute heat across the planet. Surface currents are driven by winds (trades, westerlies) and deflected by the Coriolis effect. Deep currents form the thermohaline circulation.
Climate influence
The Gulf Stream carries warm water toward Europe, softening northwestern European climate (London has milder winters than New York at the same latitude). The cold Canary Current moderates Canary Islands temperatures. Currents also condition fishing productivity and transport of Saharan dust.