The complex relationship between climate change and the oceans already affects our lives, and as the planet warms, we haven’t seen the worst of it.

On top of the world, where the North American and European continents meet, the planet’s largest waterfall swirls and tumbles over a dramatic tectonic rift. The Denmark Strait cataract is the greatest waterfall you’ve never seen, because it falls entirely under the surface of the ocean. The current of water, pushed north along the Gulf Stream and cooled by the frigid Arctic, suddenly drops 11,500 feet over a 60-mile-wide cliff between Greenland and Iceland. Because cold water sinks, this torrent descends into the deep ocean, often emerging a world away, near Antarctica. Churning waves in the Southern Ocean, driven by terrific winds, then force the water north once more, along the coasts of South and North America.

This meandering loop is known as the Atlantic meridional overturning circulation, or AMOC, a 10,000-mile-long conveyor belt of ocean currents that moves heat and water—and effectively our weather and seafood—around the globe. The loop is driven by forces such as the cold water descending in the Arctic, but as oceans warm and change, this loop could break at key points—which is bad news for the ocean’s ability to continue storing heat and keeping our planet cool. Even slight changes to the ocean’s temperature, density, and composition can have far-flung implications. Read more at the Johns Hopkins magazine.