Which one of the following ocean currents has a warming influence on the…

Ocean currents are classed as warm or cold by the temperature of the water they carry relative to the surrounding sea. A warm current originates in low-latitude, equatorial waters and flows toward higher latitudes - typically along the western margins of ocean basins (the east coast of a continent) - and it raises the temperature of the coast it washes. A cold current originates in polar or high-latitude waters and flows toward the equator - typically along the eastern margins of ocean basins (the west coast of a continent) - and it lowers coastal temperature, often bringing cold-water upwelling.

The Brazil Current flows southward along the eastern coast of South America, carrying warm, low-latitude Atlantic water to progressively higher latitudes. Transporting warm water poleward along a coast is exactly what produces a warming influence, so the Brazil Current is the one among the four that warms the neighbouring coast.

• Oyashio: flows south from the sub-Arctic Bering Sea/Sea of Okhotsk along the Kuril Islands and Japan's Pacific coast, carrying cold polar water - it cools the coast rather than warming it.

• Canaries (Canary Current): flows south-westward along north-west Africa, carrying cool water from higher latitudes and driving coastal upwelling - a cold current that lowers coastal temperature.

• Benguela: flows northward along south-west Africa, also cold and upwelling-driven - it lowers rather than raises coastal temperature.

Only the Brazil Current transports warm water poleward among the four options, so it alone produces a warming influence on the neighbouring coast.