It carries more than 100 times as much water as all the world's rivers combined. It reaches from the ocean's surface to its bottom, and measures as much as 2,000 kilometers across. It connects the Indian, Atlantic and Pacific oceans, and plays a key role in regulating global climate. Continuously swirling around the southernmost continent, the Antarctic Circumpolar Current is by far the world's most powerful and consequential mover of water.