What is the largest ocean current by volume?

The largest ocean current by volume is the Antarctic Circumpolar Current.

The Antarctic Circumpolar Current, or ACC, flows continuously eastward around Antarctica through the Southern Ocean. Its average transport is estimated at about 137 ± 7 Sverdrups, with one Sverdrup equal to one million cubic metres of water per second. That makes it the largest ocean current by volume transport.

Powerful westerly winds, known as the Roaring Forties and Furious Fifties, drive the current. Because no continent blocks its path around Antarctica, the ACC forms an uninterrupted circumpolar circulation and links the Atlantic, Indian, and Pacific Ocean basins.

The ACC is more than a fast-moving surface stream. It extends through a great depth and helps redistribute heat, carbon, nutrients, and freshwater around the planet. It is often confused with the Gulf Stream, which strongly affects North Atlantic climate but carries far less water overall.