A new study led by glaciologists at the University of California, Irvine has mapped the migration of Antarctica’s ice grounding line over a 30-year period. The research, published in Proceedings of the National Academy of Sciences, is based on satellite data from multiple international missions and reveals that while most of Antarctica’s coastline remains stable, certain regions are losing significant amounts of grounded ice.
The team found that 77 percent of Antarctica’s coastline has seen no movement in its grounding line since 1996. However, concentrated retreat in West Antarctica, the Antarctic Peninsula, and parts of East Antarctica has resulted in a loss of 12,820 square kilometers—an area comparable to about ten times the size of Greater Los Angeles—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 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.”
On average, the ice sheet has retreated from the grounding line at a rate of 442 square kilometers per year. The most significant changes were observed in West Antarctica’s Amundsen Sea and Getz sectors. In these areas, glaciers have retreated between 10 and about 40 kilometers: Pine Island Glacier moved back by 33 kilometers; Thwaites Glacier by 26 kilometers; and Smith Glacier by an exceptional 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 is 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 study used data from various 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 such as Airbus U.S., ICEYE US and ICEYE Ltd.
Co-author Bernd Scheuchl described this work as a milestone for NASA’s Commercial Satellite Data Acquisition program because it marks “the first major success involving commercial synthetic aperture radar data providers for polar research.” He added: “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. 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.”
According to their findings based on three decades’ worth of satellite records analyzed by UC Irvine researchers, around 23 percent of glaciers reaching Antarctica’s oceans are retreating rapidly—particularly those near West Antarctica’s Amundsen Sea and Bellinghausen Sea as well as Wilkes Land in East Antarctica.
While most patterns can be explained by warm ocean water moving beneath ice sheets causing them to melt from below, there remain some unexplained retreats along parts of 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 ice shelves collapsed before measurements began; glaciers such as Edgeworth lost up to 16 kilometers while others like Hektoria calved up to 21 kilometers past their original positions recorded in 1996.
The comprehensive record produced provides benchmarks necessary for improving models predicting future sea level rise. As Rignot stated: “Models have to demonstrate they can match this 30-year record to claim credibility for their projections… If a model can’t reproduce this record—the modeling team will need to go back to drawing board and figure out what boundary condition or physics are missing.”
Researchers noted that confirming high stability across much—77 percent—of Antarctic coastline helps clarify conflicting results among different measurement approaches particularly concerning East Antarctic mass balance estimates; meanwhile pinpointing zones actively losing mass assists ongoing assessments elsewhere on continent.
“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 project included scientists from UC Irvine; NASA JPL; University Grenoble Alpes (France); University Washington (Seattle); ICEYE Ltd., Finland; ICEYE U.S.; with funding support provided by NASA.
