Greenland’s Petermann Glacier is facing accelerated ice melt and an increased threat of sea level rise, according to a study by researchers from the University of California, Irvine and NASA’s Jet Propulsion Laboratory. The study found that the glacier’s grounding line, where the ice detaches from the land bed and begins floating in the ocean, shifts substantially during tidal cycles, allowing warm seawater to intrude and melt ice at an accelerated rate.
The researchers analyzed satellite radar data from three European missions, which suggested that the climate community could have been vastly underestimating the magnitude of future sea level rise caused by polar ice deterioration. The study found that as Petermann Glacier’s grounding line retreated nearly 4 kilometers between 2016 and 2022, warm water carved a 200-meter-tall cavity in the underside of the glacier, which remained there for all of 2022.
The traditional view held that grounding lines beneath ocean-reaching glaciers did not migrate during tidal cycles, nor did they experience ice melt. However, the researchers found that warm ocean water intruded beneath the ice through preexisting subglacial channels, with the highest melt rates occurring at the grounding zone.
“These ice-ocean interactions make the glaciers more sensitive to ocean warming,” said senior co-author Eric Rignot, UCI professor of Earth system science and NASA JPL research scientist. “These dynamics are not included in models, and if we were to include them, it would increase projections of sea level rise by up to 200% – not just for Petermann but for all glaciers ending in the ocean, which is most of northern Greenland and all of Antarctica.”
The Greenland ice sheet has lost billions of tons of ice to the ocean in the past few decades, with most of the loss caused by warming of subsurface ocean waters, a product of Earth’s changing climate. The findings of this study further highlight the urgency of addressing climate change and its impacts on the planet’s ice sheets and sea levels.