A study led by glaciologists at the University of California, Irvine has mapped the movement of Antarctica’s ice grounding line over the past 30 years. Using data from international and commercial satellites, researchers found that while most of Antarctica remains stable, some regions have lost a significant amount of grounded ice—equivalent to the size of Greater Los Angeles every three years.
The research, published in Proceedings of the National Academy of Sciences, shows that 77 percent of Antarctica’s coastline has not experienced grounding line migration since 1996. However, concentrated retreat in West Antarctica, the Antarctic Peninsula, and parts of East Antarctica has resulted in a loss of nearly 5,000 square miles (12,820 square kilometers) over three decades.
“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 rate of retreat from the grounding line was measured at 442 square kilometers per year. The largest changes occurred in West Antarctica’s Amundsen Sea and Getz sectors. Glaciers there retreated between 10 and about 40 kilometers: Pine Island Glacier by 33 kilometers, Thwaites Glacier by 26 kilometers, and Smith Glacier by an extraordinary 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. “It’s like the balloon that’s not punctured everywhere, but where it is punctured, it’s punctured deep.”
Researchers gathered data from several satellite missions operated by agencies including ESA (ERS-1/2 and Sentinel-1), Canada (RADARSAT series), Japan (ALOS/PALSAR), Italy (COSMO-SkyMed), Germany (TerraSAR-X), Argentina (SAOCOM), as well as commercial providers.
Co-author Bernd Scheuchl described this as a landmark achievement for NASA’s Commercial Satellite Data Acquisition program: “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.”
While much retreat can be explained by warm ocean water reaching beneath ice sheets, some patterns remain unexplained—such as along parts of the 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 area multiple ice shelves collapsed before study began; glaciers such as Edgeworth lost up to 16 kilometers while others like Hektoria calved more than 21 kilometers past their positions in 1996.
The findings offer benchmarks for future models projecting 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 also pointed out that confirming stability across much of East Antarctica helps resolve discrepancies among measurement methods there.
“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.”
The research involved scientists from UC Irvine—a university recognized for its very high research activity according to its official website—NASA JPL, University Grenoble Alpes in France, University of Washington in Seattle; collaborators from ICEYE Ltd., Finland; ICEYE U.S.; with funding support from NASA.
UC Irvine participates within NCAA Division I athletics under its Anteaters teams (source), operates within the University of California system, focuses on advancing knowledge through research and public service (source), engages internationally (source), and holds accreditation from WASC Senior College and University Commission (source).
