A Massive Freshwater River Is Flowing Under Antarctica’s Ice

The 285-mile-long stretch of meltwater is longer than the Thames and could speed ice loss

Illustration of the under-ice river
An illustration of the under-ice river Courtesy of Imperial College London

Scientists know the ice covering Antarctica is melting, but they don’t fully understand all the forces at play. Now, they’ve made a surprising discovery that might help explain ice loss across parts of the massive continent: a 285-mile-long river coursing underneath the ice.

They discovered the mysterious river by flying an aircraft over Antarctica to gather radar data, which they combined with models of how water would move on the continent. From their analysis, the team determined that the hidden river flows at three times the rate of the river Thames in London, reports Wired’s Matt Simon. Ice covering an area as big as France and Germany combined—from both the East and West Antarctic ice sheets—is slowly melting and contributing water to the river.

The find, which the team shared in a paper published in Nature Geosciences late last month, means the underside of Antarctica's ice has more active water flow than scientists previously understood. This could make it more susceptible to human-caused climate change.

“The region where this study is based holds enough ice to raise the sea level globally by 4.3 meters [14 feet],” says study co-author Martin Siegert, a natural scientist at Imperial College London in England, in a statement. “How much of this ice melts, and how quickly, is linked to how slippery the base of the ice is. The newly discovered river system could strongly influence this process.”

Researchers on Antarctica
Researchers gathered radar data via aircraft. Courtesy of Neil Ross / Imperial College London

Antarctica is remote, rugged and vast, making it extremely difficult to study. That’s part of the reason why scientists hadn’t discovered the subglacial river already. But they also didn’t expect to find one: In Greenland, for example, warm summer temperatures melt ice from the top, causing large amounts of water to flow from the surface and filter down through deep crevasses. In Antarctica, however, the summers are colder, and the ice’s surface doesn’t melt much. Because of this, scientists assumed there wouldn’t be much water underneath the ice sheets.

Instead, the research revealed Antarctia’s ice is melting from the bottom, caused by friction as it rubs against the land, as well as by natural geothermal heat from the Earth. The scientists determined that the amount of melting ice is not huge—no more than a few millimeters per year. But since the ice’s surface area is so large, even a millimeter of meltwater can add up to a massive, fast-moving river.

All of that freshwater flows into the Weddell Sea, where Antarctica’s ice sheets go from resting on land to floating on water. This transition zone, called the grounding line, is especially vulnerable to warming temperatures. Understanding more about what’s affecting this sensitive region can help researchers develop more accurate models for estimating future sea-level rise.

In fact, the discovery of the river—and its abundant flow of freshwater—helps explain a puzzling mismatch between satellite measurements and melting models. Satellites had suggested a greater amount of ice loss was occurring—and they were right.

“This paper adds a piece to the puzzle of understanding what's actually going on at the grounding line,” says Pietro Milillo, a physicist at the University of Houston who was not involved in the study, to Wired.

Finding the river, then, is a significant boost to scientists’ overall understanding of Antarctica’s subglacial hydrology. This, in turn, means they can better predict how the continent’s ice sheets may behave if global warming continues unchecked.

“This discovery could be a missing link in our models,” says study co-author Christine Dow, a glaciologist at the University of Waterloo in Canada, in a statement. “We could be hugely underestimating how quickly the system will melt by not accounting for the influence of these river systems. Only by knowing why ice is being lost can we make models and predictions of how the ice will react in the future under further global heating and how much this could raise global sea levels.”