Ice melt in polar regions is accelerating faster than scientists previously understood. The rapid retreat could lift sea levels higher than earlier forecasts, threatening coastlines across Canada, the United States, and beyond.
During investigations of the Petermann Glacier in northwest Greenland, researchers from the University of California, Irvine, and NASA’s Jet Propulsion Laboratory uncovered a surprising interaction between ice and seawater. This link points to a dynamic that has not been fully captured in prior sea level rise calculations.
Glaciologists warn that ignoring these oceanic inputs may lead to a significant underestimation of future sea level increases driven by polar ice loss. Ice retreat is accelerating in Greenland, the Arctic, and Antarctica, outpacing many climate projections in recent years.
Analysis of satellite radar data from three earlier European missions showed that the zones where the Petermann Glacier meets the land undergo meaningful changes during tidal cycles. Warm seawater moves through subglacial routes, accelerating melt where the glacier touches the ocean.
Very high melting rates
The study, published in a leading scientific journal, shows that from 2016 to 2022 the glacier retreated about four kilometers on land. The warmth of the water carved a deep hollow in the lower ice, keeping it open through 2022 and signaling ongoing melting. Ice–ocean interactions are making glaciers more vulnerable to ocean warming, a factor not fully represented in many models.
Experts say including these dynamics in future models could push sea level rise projections higher by as much as 200 percent for any glacier that contacts the ocean, not just Petermann. Greenland and Antarctica would face larger potential losses if these processes are added to forecasts, they caution.
Lead author Enrico Ciraci, an assistant scientist at UCI and a NASA postdoctoral fellow, notes that the line where ice meets water shifts by several kilometers with the tides, a magnitude much larger than expected. This finding underscores how tidal cycles can alter the stability of marine-terminating glaciers.
Aerial images show a large chunk of ice calved from the Petermann Glacier in Greenland in 2009. Reuters
Previously, it was believed that the base lines under ocean-adjacent glaciers stayed fixed during tidal cycles and would not experience notable melt. The new study challenges that idea, showing that warm ocean water can seep beneath the ice through subglacial channels, boosting melt where the glacier meets the mainland.
Irreversible ice loss
In recent years, billions of tons of Greenland ice have moved into the ocean. The report indicates much of this loss comes from groundwater warming in the sea, a consequence of long-term climate change. Warmer water infiltrates the ice front, eroding resistance and hastening movement toward the water.
Researchers also point to similar processes beneath West Antarctica, where rapid retreat has been linked to mechanisms under floating ice shelves. Observations from the Thwaites Glacier region show that cracking zones are melting faster than expected, contributing to notable retreat since the late 1990s.
A recent study notes that most of the ice sheet sits below sea level and remains vulnerable to rapid, irreversible loss that could lift global sea levels by more than half a meter over the coming centuries. Warm water entering through cracks helps erode the glacier at its weakest points.
Key reports reference the Petermann Glacier and Thwaites Glacier as crucial cases for understanding how submarine processes influence surface melt and retreat. These findings stress the need to include ocean-driven dynamics in assessments of future sea level rise. Citation: Petermann Glacier study, Proceedings of the National Academy of Sciences Citation: Thwaites Glacier study, Nature
Environmental authorities and researchers continue to monitor polar ice changes with a focus on how ocean warming interacts with glacier fronts. The evolving understanding underscores the urgency of addressing climate drivers that drive ice loss and threaten coastal resilience.