Ice piracy: Antarctic glacier discovered 'stealing' ice from its neighbor, and that's not a good thing

A new phenomenon dubbed “ice piracy” is unfolding in the frigid wilderness of West Antarctica, where one glacier appears to be stealing ice from its neighbor.

This unusual behavior – once believed to take hundreds or even thousands of years – has now been recorded happening in under two decades.

Scientists from the University of Leeds, working with international collaborators, have used high-resolution satellite data to reveal that a fast-moving glacier is redirecting ice flow away from its slower neighbor.

This surprising event is changing how scientists understand the dynamics of glaciers – and how such shifts may contribute to future sea-level rise. Their findings, now published in The Cryosphere, provide rare insight into these rapid changes.

Fast-paced shift in the ice

Between 2005 and 2022, researchers observed that seven ice streams in the Pope, Smith, and Kohler (PSK) region of West Antarctica sped up significantly.

One glacier nearly doubled its speed – an 87% increase – at the point where it meets the ocean.

Three other glaciers accelerated by 60% to 84%. By 2022, six of these streams were moving at more than 700 meters (0.4 miles) per year. That’s the equivalent of covering just over seven football fields in just one year.

This kind of acceleration, especially so close to the grounding line – the point where a glacier starts to float – is a warning sign.

Grounding lines help track the stability of ice sheets. Changes in their position or speed suggest the system is out of balance and can influence how ice flows inland.

Slowing glaciers leads to ice piracy

But not every glacier followed the same pattern. The Kohler West glacier actually slowed down by 10% during the same time period.

This stood in stark contrast to nearby glaciers like Kohler East and Smith West, which sped up dramatically – by about 560 meters per year.

The slowdown puzzled scientists, until they looked at the ice flow patterns.

Kohler West and Kohler East

“We think that the observed slowdown on Kohler West Glacier is due to the redirection of ice flow towards its neighbor – Kohler East,” explained lead author Dr. Heather L. Selley from the University of Leeds.

“This is due to the large change in Kohler West’s surface slope, likely caused by the vastly different thinning rates on its neighboring glaciers.”

She added that because Kohler East’s ice stream is flowing and thinning faster as it travels, it absorbs, or ‘steals’ ice from Kohler West.

“This is effectively an act of ‘ice piracy’, where ice flow is redirected from one glacier to another, and the accelerating glacier is essentially ‘thieving’ ice from its slowing neighbor,” explained Selley.

“We didn’t know ice streams could ‘steal’ ice from each over such a short period, so this is a fascinating discovery. It’s unprecedented as we’re seeing this from satellite data and it’s happening at a rate of under 18 years, whereas we’ve always thought it was this extremely long, slow process,” she added.

Watching ice piracy from space

To track this shift, the research team used satellite images and a technique that follows the movement of surface features like crevasses and rifts.

They also incorporated data on ice thinning from the European Space Agency’s CryoSat mission.

Data was sourced from satellites operated by ESA, NASA, the Canadian Space Agency, and the Japan Aerospace Exploration Agency.

“This study provides an interesting demonstration of ice piracy, where flow into one glacier gradually switches to flow into another glacier, as the ocean melts the grounding zone and re-configures ice flow,” said Pierre Dutrieux, climate researcher at the British Antarctic Survey.

Why does any of this matter?

The research team looked into several factors that influence ice flow, including ocean temperatures, circulation changes, air temperature, and snowfall.

They discovered that ice redirection is affecting the amount of ice reaching the floating ice shelves fed by these glaciers.

Two major ice shelves – the Crosson and Dotson – are already among the fastest-changing outlets in West Antarctica.

Crosson spans roughly 40 miles (60 kilometers), and Dotson stretches about 30 miles (48 kilometers). Both are thinning and retreating at their grounding lines.

“The changes in flow direction have substantially altered the ice mass flux into Dotson and Crosson Ice Shelves, likely playing an important role in maintaining Dotson and accelerating the deterioration of Crosson,” explained Professor Anna Hogg, co-author and Professor of Earth Observation at the University of Leeds.

“This suggests that ice flow redirection is an important new process in contemporary ice sheet dynamics, which is required to understand present-day structural change in glaciers and the future evolution of these systems.”

Ice piracy, rising seas, global impacts

The stakes are high. Sea levels are already rising due to climate change, and over 410 million people could be affected by coastal flooding by the year 2100. Global sea levels have increased by more than 10 centimeters over the past decade.

“This new study highlights the unique ability of satellites to provide both the temporal and spatial coverage required to assess change in the polar regions,” remarked Dr. Martin Wearing, ESA Digital Twin Earth Scientist and Polar Science Cluster Coordinator.

Using data from Copernicus Sentinel-1 and ESA’s Earth Explorer CryoSat, the team has revealed the complex evolution of ice flow in part of West Antarctica over the past few decades.

Understanding these changing dynamics and what drives them is crucial for improved projections of future ice-sheet change and contributions to sea-level rise.

What does it all mean?

To sum it all up, the Antarctic ice sheet – once thought to be sluggish and stable over millennia – is changing much faster than we realized, and in unexpected ways.

This discovery of “ice piracy” shows that glaciers can dynamically interact, competing for ice and rerouting flow like rivers shifting course, which completely reshapes how we model future sea-level rise.

If one glacier can weaken another by stealing its ice, entire ice systems may destabilize quicker than predicted, feeding more ice into the ocean and raising sea levels.

In plain terms: Antarctica isn’t just melting – it’s reorganizing itself in ways that could have big consequences for coastal cities around the world.

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The study brought together experts from the University of Leeds, the British Antarctic Survey, and the UK Centre for Polar Observation and Modelling (CPOM), which is led from Northumbria University.

The full study was published in the journal The Cryosphere.

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