Antarctica's Shifting Ice: A 30-Year Satellite View

A major new study using satellite data has found that Antarctica has lost a huge area of ice over the past 30 years. The ice that has disappeared is called "grounded ice," which is ice that sits on the bedrock of the continent. The lost area is about 5,000 square miles (12,950 square kilometers). That is an area nearly twice the size of the state of Delaware. The ice is melting because warmer ocean water is eating away at Antarctica's edges.

Scientists from the University of California, Irvine, led the research. They tracked changes to Antarctica's "grounding line" from 1992 to 2025. The grounding line is a very important boundary. On one side, ice is firmly attached to the bedrock. On the other side, ice begins to float on the ocean, forming what are called ice shelves. When this grounding line moves inland, it means land-based ice is starting to float. This ice then directly adds to rising sea levels. Tracking this line helps scientists understand the stability of Antarctica's ice sheets.

"We've known it's critically important for 30 years, but this is the first time we've mapped it comprehensively across all of Antarctica over such a long time span," said the study's lead author, Eric Rignot of UC Irvine.

To find the grounding line, Rignot and his team used data from many different satellites. These satellites are operated by space agencies in Europe, Canada, Japan, Italy, Germany, and Argentina. The scientists used radar instruments to watch how the floating ice shelves moved up and down with the ocean tides. The grounded ice, stuck to the bedrock, did not move with the tides. By comparing these movements, the researchers could pinpoint the exact location of the grounding line over three decades with great precision.

The results show a complex story. About 77% of Antarctica's coastline showed no detectable movement of the grounding line since 1996. This suggests that large parts of the continent are stable. However, in more vulnerable regions, the study found "significant retreat." This means the grounding line moved inland, and ice was lost.

The most dramatic changes happened in West Antarctica and in an area called the Getz sector. Along the Amundsen Sea coast, the grounding line pulled back by as much as 26 miles (42 kilometers) in some places over the study period.

Eric Rignot explained why retreat happens fastest in certain spots. He said deep underwater channels act like pathways, funneling warm ocean water toward the base of glaciers. This warm water melts the ice from below. This thins the floating ice shelves and weakens their ability to hold back the glaciers on land behind them.

"It's like the balloon that's not punctured everywhere, but where it is punctured, it's punctured deep," Rignot said.

The study also revealed a mystery. Along the northeast Antarctic Peninsula, several ice shelves collapsed before the study began. Since then, many glaciers there have retreated a lot. But scientists do not have clear evidence that warm ocean water is causing this change.

"Something else is acting — it's still a question mark," Rignot said.

This new map of grounding line changes is more than just a history lesson. The researchers say it provides a crucial real-world test for the computer models that predict future sea level rise.

"Models have to demonstrate they can match this 30-year record to claim credibility for their projections," Rignot said. "That's the real value of this observational record: knowing that this grounding line migration has happened."

While most of Antarctica is currently stable, Rignot warned that this balance may not last forever. The areas that are retreating are a sign of what could happen more widely if ocean warming continues.

"The flip side is that we should perhaps feel fortunate that all of Antarctica isn't reacting right now, because we would be in far more trouble," he said. "But that could be the next step."