Researchers from the University of California, Irvine, and NASA’s Jet Propulsion Laboratory have made a significant discovery regarding the interaction between ice and the ocean at Petermann Glacier in northwest Greenland. Their findings, published in the Proceedings of the National Academy of Sciences, suggest that the impact of polar ice deterioration on future sea-level rise may have been greatly underestimated by the scientific community.
By analyzing satellite radar data from European missions, the UCI/NASA team observed that the grounding line of Petermann Glacier, where ice separates from the land bed and floats in the ocean, undergoes substantial shifts during tidal cycles. This movement allows warm seawater to intrude and accelerate the melting of ice. The researchers found that the grounding line of Petermann Glacier migrates between 2 and 6 kilometers as tides ebb and flow, a magnitude much larger than previously believed for grounding lines on a rigid bed.
The traditional understanding of grounding lines beneath ocean-reaching glaciers was that they did not migrate during tidal cycles and did not experience ice melt. However, this study challenges that perception by demonstrating that warm ocean water infiltrates beneath the ice through existing subglacial channels, with the highest rates of ice melt occurring at the grounding zone.
Between 2016 and 2022, the grounding line of Petermann Glacier retreated by nearly 4 kilometers, resulting in warm water carving a 670-foot-tall cavity on the underside of the glacier. This cavity persisted throughout 2022.
These ice-ocean interactions increase the sensitivity of glaciers to ocean warming, according to Eric Rignot, a senior co-author of the study and a UCI professor of Earth system science and NASA JPL research scientist. Importantly, these dynamics have not been accounted for in current models, and if included, they could raise projections of future sea-level rise by up to 200 percent for not only Petermann Glacier but also for all glaciers terminating in the ocean, including those in northern Greenland and Antarctica.
The Greenland ice sheet has experienced substantial ice loss over recent decades, with the majority attributed to warming of subsurface ocean waters, a consequence of climate change. Exposure to ocean water intensifies ice melting at the glacier front and weakens resistance to glacier movement, leading to faster ice flow into the sea.
Source: University of California, Irvine
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