Far beneath the waves of the stormy Southern Ocean, cold, salty water plunges off Antarctica’s continental shelf like a silent underwater waterfall, fueling a vast ocean current system that helps regulate Earth’s climate. Long hidden and nearly impossible to observe, these dense water cascades are finally being seen not by ships or divers, but from space.
In a groundbreaking study, researchers have used satellite data to track these powerful underwater flows by spotting tiny dips in sea level often just a few centimetres. These subtle signals, detected by satellites orbiting hundreds of kilometres above Earth, mark the sinking of cold, heavy water as it plunges to the ocean floor. This discovery opens up a low-cost, carbon-free way to monitor one of the ocean’s most important but elusive systems.
What Are These Underwater Waterfalls?
The Southern Ocean, circling Antarctica, is home to an essential process in the planet’s climate system. When sea ice forms, it pushes out salt, making the nearby water heavier. This dense water then flows across the continental shelf and eventually tumbles down steep underwater cliffs, forming what scientists call “dense water cascades.” These flows travel along the ocean floor, carrying oxygen, heat, carbon, and nutrients from the surface into the deep sea.
This deep ocean movement is part of the global ocean overturning circulation sometimes called the planet’s conveyor belt which helps balance global temperatures and carbon levels.
A Threat from Melting Ice
But this system is slowing down. As climate change melts the Antarctic ice sheet, it adds fresh water to the ocean, diluting the salty water and making it harder for dense water to form. Studies have already shown a 30% slowdown in deep-sea circulation, which could weaken further in the coming years. That means less carbon and heat being absorbed by the oceans and faster climate change.
Tracking these changes is vital, but until now, scientists relied on expensive and limited tools like deep-sea moorings, ship surveys, and even sensors attached to seals. These methods provide rich local data but are costly, time-consuming, and can’t cover the vast, icy Southern Ocean.
That’s where satellites come in. Using European Space Agency satellites like CryoSat-2 and Sentinel-3A, scientists can now measure sea surface height with centimetre-level accuracy even in icy waters. Thanks to advanced data processing, researchers can look through cracks in the sea ice called “leads” to measure the sea surface below.
In this new study, scientists focused on the Ross Sea, a key area for dense water formation. They combined nearly ten years of satellite data with detailed ocean models and discovered that the dense water plunges leave a small, but consistent dip in sea level. These dips align with previous data gathered from ships and underwater sensors, confirming that satellite tracking is a reliable method.
This marks the first time these Antarctic underwater waterfalls have been monitored from space. Unlike traditional methods, satellite monitoring is wide-reaching, low-cost, and has zero carbon emissions making it a valuable tool in the fight against climate change.
As Antarctica continues to change, keeping track of how its underwater currents behave will be crucial. These currents play a key role in how much heat and carbon the ocean can absorb, directly affecting the planet’s climate future.
With satellites now providing a clear view into these hidden flows, scientists have a new, powerful way to monitor one of Earth’s most critical and most mysterious climate regulators.