Resurrection Glacier is melting at rates exceeding previous expectations

New research conducted by a team of glaciologists indicates that the largest glacier on the planet is melting at a “more rapid pace” than previously expected, meaning that its effects on global sea level rise may be twice as high as current estimates. The Thwaites Glacier in West Antarctica, nicknamed the "Doomsday River" due to the catastrophe its collapse could cause, is a critical unknown when trying to predict global sea level rise.

This glacier, which is the size of the US state of Florida and is located in one of the most inaccessible areas on Earth, has been declining for decades, and its melting is currently contributing 4% to global sea level rise. But the mechanisms behind this decline are very complex, making it difficult to predict its future.

This issue is very important, as the Thwaites River contains enough water to raise sea levels by more than 0.6 meters if it collapsed. Since it also acts as a “plug” that holds back Antarctica’s massive ice sheet, its collapse could cause sea levels to rise by about 3 metres, which would have devastating effects on coastal communities, from the city of Miami in America to the Philippine capital, Manila.

Glaciologists from the University of California, Irvine, and NASA's Jet Propulsion Laboratory have developed a new model of the ice sheet, which they say more accurately reflects what is happening under this huge ice mass. The rapid retreat of the Thwaites River is due to processes occurring at what is known as the fulcrum, the point at which the ice breaks off from the sea floor and begins to float above the ocean in the form of an ice shelf.

While traditional models of ice sheets have treated the fulcrum as a largely fixed and stable boundary, “we found that there is a different order to what happens below major glaciers that terminate in the oceans,” said UCLA project scientist and lead author of the study, Mattia Buinelli, who was an Earth system scientist at UC Irvine at the time of the study. Satellite data reveal that the so-called “fulcrum line” is actually a “fulcrum zone” that can sometimes extend for miles, where seawater constantly flows in and out with the tides, raising and lowering thick layers of ice in a process known as “tidal pumping.”

This allows relatively warm ocean water to penetrate “deep beneath the ice sheets, causing powerful melting,” Buinelli explained. When scientists modified their models to include the concept of a "supercenter", they found that the Thwaites Glacier could contribute to a sea level rise of up to 3 centimeters by 2100, double previous estimates, even in the absence of further global warming, according to results published Monday in the journal Nature Communications.

The land on which the Thwaites River rests slopes downward, meaning that as the ice melts, more of it is exposed to warm ocean waters. However, the area's topography is further complicated by the presence of two major underwater ridges, which serve to "stabilize" the ice and prevent it from sliding more quickly into the ocean.

The study indicates that melting processes in the Thwaites River “focus” lead to accelerating the process of ice “liberation” from a large elevation known as “Mouginot Ridge.” It also estimates the possibility of ice freeing from this highland at about 60% by the end of the century.

The glacier will then likely retreat rapidly along the sloping bedrock it rests on toward the next major rise. These findings suggest that the implications of losing the Thwaites River have been underestimated - 3cm of sea level rise may seem small, but it is enough to dramatically magnify the risks faced by coastal populations.

Eric Reneau, one of the study's authors and a professor of Earth system sciences at the University of California, Irvine, says the results "predict a greater risk of coastal flooding, and that coastal areas will be more vulnerable to these risks than expected in the coming decades." For his part, Ted Scambos, a senior researcher at the Center for Earth Sciences and Observation at the University of Colorado in Boulder, USA, who was not involved in this research, believes that these results may constitute “a real turning point in sea level rise projections associated with the Thwaites River.”

But he, along with other experts, stressed the need to conduct more research to understand the effects of different melting processes in the "focal zone", especially by obtaining direct data from under the glacier. Renew said the next step was to obtain observational data from the Thwaites River 'anchor line'.

Scientists plan to head there in 2028 to deploy devices capable of monitoring the movement of seawater flowing in and out. “We have been aware of the effects of climate change on our planet's delicate ice sheets for decades, but growing awareness in recent years of what is actually happening in the lower parts of glaciers, such as the Thwaites, raises much greater concern,” Renew said.

He also added that we must immediately reduce the pollution causing global warming to limit these effects, but he warned: “Even if we do this, we are expected to see a rise in sea levels in the future, as a result of the damage that has already occurred.”