A three-decade study led by glaciologists at the University of California, Irvine has mapped the movement of Antarctica’s ice grounding lines, revealing that certain regions have experienced significant retreat. The research used satellite data collected over 30 years to assess how much grounded ice—ice resting on land rather than floating—has been lost.
According to the study, published in Proceedings of the National Academy of Sciences, 77 percent of Antarctica’s coastline has not seen changes in its grounding line since 1996. However, areas such as West Antarctica, the Antarctic Peninsula and parts of East Antarctica have collectively lost about 12,820 square kilometers (nearly 5,000 square miles) of grounded ice over this period. This loss is equivalent to approximately ten times the size of Greater Los Angeles.
“The grounding line is where continental ice meets the ocean, and measuring the movement of grounding lines with satellite-based synthetic aperture radar has been our gold standard for documenting ice sheet stability,” said lead author Eric Rignot, UC Irvine distinguished professor and Donald Bren Professor of Earth system science. “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.”
The average annual retreat rate from these areas was measured at about 442 square kilometers per year. Some glaciers in West Antarctica saw especially pronounced changes: Pine Island Glacier retreated by 33 kilometers; Thwaites Glacier by 26 kilometers; Smith Glacier by 42 kilometers.
“Where warm ocean water is pushed by winds to reach glaciers, that’s where we see the big wounds in Antarctica,” explained Rignot, who’s also a senior research scientist at NASA’s Jet Propulsion Laboratory. “It’s like the balloon that’s not punctured everywhere, but where it is punctured, it’s punctured deep.”
The researchers compiled their findings using data from several international satellite missions operated by agencies including those from Europe (ESA), Canada (RADARSAT), Japan (ALOS/PALSAR), Italy (COSMO-SkyMed), Germany (TerraSAR-X), and Argentina (SAOCOM).
Bernd Scheuchl, UC Irvine project scientist in Earth system science and co-author on the paper, noted that this work marks an important milestone for NASA’s Commercial Satellite Data Acquisition program because it demonstrates how commercial synthetic aperture radar data can support polar research alongside government-run missions.
“This work shows how commercial SAR data can be used to contribute to the virtual SAR constellation by augmenting the program of record from agency-run missions,” Scheuchl said. “The ability to access daily observations in critical areas using commercial assets, combined with decades of international space agency data with large-area coverage, has opened a new era in polar monitoring.”
The study also found that nearly a quarter—23 percent—of Antarctica’s ocean-reaching glaciers are undergoing rapid retreat. The greatest losses were observed near West Antarctica’s Amundsen Sea and Bellinghausen Sea as well as Wilkes Land in East Antarctica.
While most patterns could be attributed to incursions of warm ocean water under ice sheets causing melting from below, some unexplained retreats were documented along sections like northeast Antarctic Peninsula.
“A lot of these places have warm ocean water in proximity, but on the east coast of the peninsula there’s substantial retreat and we don’t have evidence for warm water,” Rignot said. “Something else is acting – it’s still a question mark.”
In this region several glaciers—including Edgeworth (16 kilometers lost), Boydell, Sjogren, Bombardier and Dinsmoor—have significantly retreated following previous collapses of local ice shelves prior to 1996.
According to researchers involved in this project—which included participants from UC Irvine; NASA JPL; France’s University Grenoble Alpes; University of Washington; ICEYE Ltd., Finland; and ICEYE U.S.—the newly assembled record will help improve next-generation models aimed at predicting future sea level rise.
“Models have to demonstrate they can match this 30-year record to claim credibility for their projections,” Rignot noted. “That’s the real value of this observational record: knowing that this grounding line migration has happened. If a model can’t reproduce this record, the modeling team will need to go back to the drawing board and figure out what boundary condition or physics are missing.”
Researchers emphasized that confirming most Antarctic coastline remains stable provides clarity when interpreting conflicting measurements elsewhere on the continent. They added that knowing exactly which sectors are losing mass allows scientists worldwide better insight into current changes affecting global sea levels.
“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,” Rignot said. “But that could be the next step.”
NASA provided funding support for this work.
