Hidden rivers beneath Antarctic ice reshape sea-level predictions

Many people think of Antarctica as an unchanging mass of ice. Scientists, however, know that its hidden underbelly is active and unpredictable.

A new investigation that was based on 34 million years of data suggests that we would be wise to take note of these dynamic phenomena as subglacial water movements may reshape our understanding of future sea-level changes.

“Many studies say the past is an analogue of what might happen in the future,” said Anna-Mireilla Hayden, a PhD candidate from the University of Waterloo, and first author of the study. She noted that ignoring the invisible waterways under the ice could lead to big surprises.

Hayden worked alongside Dr. Tyler Pelle from Scripps Institute of Oceanography in the U.S., and other experts, to understand how these secret river systems evolve over time.

Subglacial rivers shape Antarctica’s ice

Antarctica is more than just a block of ice. Beneath its frozen surface, water travels through channels deep below the ice sheet. The subglacial water moves with a force that scientists have rarely factored into the usual models of sea-level change.

The researchers focused on the Aurora Subglacial Basin which, if fully melted, might push global sea levels up by about 13 feet (4 meters).

Water flow data and sea-level predictions

Scientists already knew that warm ocean waters can melt floating ice shelves from below. However, the recent findings indicate that water flow at the base of the ice adds another layer of complexity to the story.

“It’s important that scientists who model ice sheets account for hydrology because it could reduce uncertainty in estimates of sea-level rise,” said Hayden.

The group noticed that underground rivers have shifted repeatedly, and have influenced how and where the ice might thin or break.

Ocean impact and ice shelf melting

The shape and path of these subglacial networks matter because they can channel fresh water into the sea at sensitive spots. When cold, fresh water pours out at certain areas beneath ice shelves, it can disrupt the usual ocean patterns and speed up local ice thinning.

Climate experts have often focused on air temperatures or large-scale currents in their models. Fresh water cycling under the ice is now emerging as a hidden factor that could make existing estimates of sea-level rise less certain.

A call for global awareness

“It’s critical that projections of sea-level rise include as much relevant information as possible so that the world can take appropriate measures to lessen the devastation to global coastal communities,” said Dr. Christine Dow, a professor at the University of Waterloo.

Dr. Dow pointed out that these findings underscore how fragile the balance really is under Antarctica’s frozen surface. Her team does not expect the ice sheet to give way overnight, but shifts under the glaciers can make them more prone to breaking off faster.

With coastal areas around the globe already facing erosion and higher flooding risks, the science community sees this as a reminder that small tweaks in the environment can yield very large consequences.

Forecasts need subglacial water insights

Going forward, experts suggest that any attempts to forecast future sea levels take these long-buried waterways into account. Models that leave out the subglacial picture could be missing critical pieces of how glaciers might evolve as temperatures warm.

The researchers say further work is needed to track how the flow beneath the ice might accelerate or change direction in the next few decades. Understanding these rivers could help refine local and global strategies for coastal planning.

What the past reveals about the future

The study showed that subglacial drainage systems, which influence sea level, have never stayed in one configuration for long. As the climate shifted over millions of years, so did the routes and volumes of meltwater flowing beneath the ice.

During a period known as the Eocene-Oligocene Boundary, 34 million years ago, long underground rivers carried high volumes of water under thick ice.

Surprisingly, the predicted drainage patterns for 2100 under extreme warming closely resemble those ancient conditions, even though they are derived from opposite climate extremes

The study is published in the journal Nature Communications.

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