The University of California, Irvine and NASA's Jet Propulsion Laboratory discovered a new ice-ocean interaction while studying northwest Greenland's Petermann Glacier.
Glaciologists found that the climate community overestimated the anticipated sea level rise from polar ice melting. The UCI/NASA collaboration found that Petermann Glacier's grounding line is very tide-dependent. Warm seawater melts the ice faster. Three European planes' satellite radar data revealed this. Team research was summarized in Proceedings of the National Academy of Sciences.
Enrico Ciraci, a NASA postdoctoral researcher at the University of California, Irvine and assistant specialist in Earth system science, says "Petermann's grounding line is better called a grounding zone because it moves between 2 and 6 kilometers as the tides rise and fall." This is substantially larger than what is used to ground solid surfaces. He said it is a common misperception that grounding lines beneath glaciers that reach the ocean do not change or suffer glacial discharge. Melting occurs most often around the grounding zone where warm ocean water penetrates the ice through channels.
Warm water excavated a 212-mile-long (670-foot) dip in Petermann Glacier's bottom between 2016 and 2022 as its grounding line moved. Experts found the hole in 2022. Eric Rignot, NASA JPL research scientist and University of California, Irvine professor of Earth system science, says these ice-water interactions make glaciers more vulnerable to ocean warming. If these changes were considered in models, Petermann and all glaciers that finish in the ocean, including most of northern Greenland and all of Antarctica, would see a 200 percent higher sea level increase.
According to a PNAS study, the Greenland ice sheet has lost billions of tons of ice to the ocean during the previous several decades. This loss is primarily due to climate change warming the ocean's deep waters. Rignot claims that ocean water melts the glacier front's ice quickly, allowing it to spread over land. The glacier falls faster into the lake.