Key Points
- Researchers have discovered a new way in which ice and the ocean interact at Petermann Glacier in northwest Greenland.
- The traditional view of grounding lines beneath ocean-reaching glaciers was that they did not migrate during tidal cycles, nor did they experience ice melt, but the new study found the opposite.
- The researchers found that including these dynamics in models could increase projections of sea level rise by up to 200 percent for all glaciers ending in the ocean.
A group of researchers from the University of California, Irvine and NASA’s Jet Propulsion Laboratory have uncovered a surprising new way in which ice and the ocean interact. They have been studying the Petermann Glacier in northwest Greenland and their findings show that the ice and ocean behave in ways previously unknown. The researchers said their discovery means that the climate community has been underestimating the magnitude of future sea level rise caused by polar ice deterioration. Their results have been published in Proceedings of the National Academy of Sciences.
The team used satellite radar data from three European missions to learn about the Petermann Glacier’s grounding line. They found that the glacier’s grounding line shifts substantially during tidal cycles, which allows warm seawater to intrude and melt ice at an accelerated rate. This means that warm ocean water intrudes beneath the ice through pre-existing subglacial channels, with the highest melt rates occurring at the grounding zone.
The researchers found that as Petermann Glacier’s grounding line retreated nearly 4 kilometers between 2016 and 2022, warm water carved a 670-foot-tall cavity in the underside of the glacier, and that abscess remained there for all of 2022. These ice-ocean interactions make the glaciers more sensitive to ocean warming, according to senior co-author Eric Rignot, UCI professor of Earth system science and NASA JPL research scientist.
The traditional view of grounding lines beneath ocean-reaching glaciers was that they did not migrate during tidal cycles, nor did they experience ice melt. But the new study replaces that thinking with knowledge that warm ocean water intrudes beneath the ice through preexisting subglacial channels, with the highest melt rates occurring at the grounding zone.
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. The researchers found that these dynamics are not included in models, and if they were included, it would increase projections of sea level rise by up to 200 percent – not just for Petermann but for all glaciers ending in the ocean, which is most of northern Greenland and all of Antarctica.
Enrico Ciraci, UCI assistant specialist in Earth system science and NASA postdoctoral fellow, said that their findings could help improve models and projections for future sea level rise. He was supported by the NASA Postdoctoral Program at the Jet Propulsion Laboratory, along with other researchers from the University of California, Irvine, Finland’s Iceye mission, China’s Tongji University, the University of Houston, the German Aerospace Center, and the Italian Space Agency.
