Antarctica retreat study signals future ice loss

Scientists studying Antarctica have gained new insights into how the world’s biggest ice sheet is reacting to warming sea temperatures. While the Antarctic Ice Sheet remained stable along more than three-quarters of its coastline over the past three decades, there are areas of significant ice retreat, sending a warning of future ice loss, according to the study based on data from several missions including Copernicus Sentinel-1.

The research, published in Proceedings of the National Academy of Sciences (PNAS), provides the most comprehensive record to date of changes in Antarctica’s ‘grounding lines’, the critical boundaries between ice resting on land and ice floating in the ocean. Grounding lines are highly sensitive to sea-level rise and are a key indicator of ice-sheet stability and ice mass loss.

The study uses three decades of radar satellite observations to map changes in grounding lines around the Antarctic continent from 1992 to 2025. It found that grounding lines were stable along more than 77% of Antarctica’s coastline, including major ice shelves such as Ross, Filchner-Ronne and Amery.

While this does not sound like bad news, the research also detected significant retreat in vulnerable regions, particularly in West Antarctica, parts of East Antarctica and the Antarctic Peninsula. The largest detected grounding line retreat was observed along the coast of the Amundsen Sea, in West Antarctica, where the ice withdrew in some places by up to 42 km over the study’s period. The most affected regions were near the East Getz, Smith, Thwaites and Pine Island ice sheets. Overall, Antarctica lost approximately 12 800 sq km of grounded ice between 1996 and 2025, which is an area equivalent to almost half the size of Belgium.

Scientists found that ice retreats to a greater extent where warm ocean currents, known as Circumpolar Deep Water, reach deep glacier beds through underwater channels. These regions are especially sensitive because the bedrock slopes downward inland, making glaciers more vulnerable to continued retreat. The results also show that the grounding line is not a fixed boundary but part of a wider ‘grounding zone’ that shifts over time due to ocean tides and subglacial water processes. The research therefore maps not just grounding lines, but grounding zones to account for variations during tidal and seasonal cycles.

The study’s lead author, Eric Rignot, of the University of California, Irvine, said, “This work would not have been possible without the unconditional support of international agencies to make observations of the polar regions available to us. As satellite observation capabilities continue to expand, we are looking forward to learning more about the dynamics of these systems so we can better project how they influence sea-level rise in the future.”

Detecting grounding line migration from space

The research demonstrates how long-term Earth observation from space is essential for monitoring the stability of the Antarctic Ice Sheet and understanding its response to climate change.

Satellites such as those in the Sentinel-1 constellation carry synthetic aperture radar, or SAR, instruments. By using differential interferometry – a technique that calculates the difference in two or more radar signals taken over the same point on Earth at different times – small differences in ground movement can be calculated, even down to a few millimetres. These small changes in ground elevation can be measured across wide areas.

In the study of Antarctica’s grounding lines, the researchers measured precise vertical movements of the floating ice shelves around the continent. They were able to measure small rises and falls of ice elevation due to tides – while the grounded ice, resting on bedrock, remained fixed. These measurements over three decades enabled the team to ascertain fluctuations in grounding lines at an unprecedented level of precision.

As well as measurements from Sentinel-1, data was also analysed from ESA’s European Remote-Sensing (ERS) satellites, as well as from the Canadian RADARSAT, Japan’s ALOS PALSAR, together with the Italian Cosmo-SkyMed, DLR’s TerraSAR-X, Argentina’s SAOCOM, and the ICEYE constellation. The aggregation of legacy missions, public data such as Sentinel-1, and commercial radar datasets demonstrates the strength of a coordinated Earth observation system.

Radar instruments can image Earth’s surface through clouds and in darkness, making them particularly useful for monitoring areas prone to long periods without sunlight, such as polar regions.

“By combining multiple satellite missions into a consistent long-term dataset, researchers have established a benchmark for future modelling efforts,” noted ESA’s Sentinel-1 Mission Manager, Nuno Miranda. He added, “This study sets a cornerstone for our understanding of grounding line dynamics. It provides a robust reference record that enables the scientific community to test predictions and improve ice sheet models, which directly inform sea-level rise scenarios and their implications for society. Continuous Earth observation remains essential to refine projections and monitor how Antarctica responds to a warming climate. ESA is proud that several European missions have played a central role in this achievement and confirms Sentinel-1 as a pillar of polar science.”