Rethinking the "Doomsday Glacier": Researchers Question Alarming Predictions of Antarctic Ice Collapse

Positive news concerning Earth's climate has been scarce in recent years due to the prevalence of frightening occurrences such as strong heat waves, destructive floods, powerful hurricanes, and blazing wildfires.

However, a recent study conducted by Dartmouth emphasizes that while the accelerated loss of ice from Greenland and Antarctica is terrible, it is highly improbable that the planet's oceans will rise to one of the absolute worst projections as the polar ice sheets melt.

The Ice Sheet Collapse Predictions' Actuality

To assess the most recent climate research and forecast the long- and short-term implications of the climate issue, the Intergovernmental Panel on Climate Change (IPCC) of the United Nations released a high-profile report that included a new and concerning prognosis. This study undermines the IPCC's projection.

The IPCC's sixth assessment report, which was published in full last year, presented a scenario in which Antarctica's contribution to the average global sea level would increase if the ice sheets on the southern continent collapsed.

Even though the IPCC rated this particular forecast as "low likelihood," it was included in the report due to the possibility that the world's oceans could rise as much as 50 feet, as the model predicts. With the exception of a narrow strip of interior high ground that runs from Gainesville to the north of Lake Okeechobee, the Florida Peninsula would be completely flooded at that magnitude, engulfing the coastal towns of the state.

However, that forecast is predicated on a novel theoretical theory regarding the retreat and disintegration of ice sheets, which are the dense, land-based glaciers that envelop polar regions. The researchers note in the journal Science Advances that the mechanism called the Marine Ice Cliff Instability (MICI), has not been observed and has only been evaluated with one low-resolution model thus far.

Rather than using MICI, the researchers test it using three high-resolution models that better represent the intricate dynamics of ice sheets. They recreated the retreat of the 75-mile-wide Thwaites Glacier in Antarctica, which is known as the "Doomsday Glacier" due to its rapid melting and potential to raise global sea levels by more than two feet. According to their models, it is improbable that the Thwaites, which are in danger, will collapse as quickly as MICI predicts in the twenty-first century.

Predictions' Effect on Legislation and Actual Decisions

The corresponding author of the research, Mathieu Morlighem, is a professor of earth sciences at Dartmouth. He stated that the results imply that the physics supporting the extreme projection in the IPCC report is erroneous, which could have practical implications. According to Morlighem, policymakers occasionally utilize these high-estimation models while debating the building of physical barriers like sea walls or even the relocation of residents of low-lying locations.

People's lives are genuinely being altered by these forecasts. These models are used by planners and policymakers, who often focus on the highest risk. When the threat proves to be much more serious than they initially believed, they are unwilling to develop remedies, according to Morlighem.

He goes on, "We're not claiming that sea-level rise won't continue or that the Antarctic is safe—all of our estimates show a rapid retreat of the ice sheet. However, high-end estimates are crucial for coastal planning, and we need them to be physics-accurate. In this instance, we are aware that this ambitious prediction for the twenty-first century is improbable.

Additional Investigation and Persistent Issues

In addition to researchers from the University of Michigan, the Universities of Edinburgh and St Andrews in Scotland, Northumbria University and Stirling in England, and the University of Michigan, Morlighem collaborated with Hélène Seroussi, an associate professor at Dartmouth's Thayer School of Engineering.

The premise behind MICI is that the ice cliffs that make up the ice sheet's outer edge could become exposed and unsupported if an ice shelf—a floating extension of the land-based ice sheet—collapses quickly. The ice sheet would slide inward towards the interior like a line of dominoes if these cliffs were tall enough to collapse under their weight, exposing a taller cliff and causing a rapid retreat.

The anticipated sharp rise in sea level would result from this ice melting and being lost to the ocean.

Yet according to the Science Advances study's authors, the glacial collapse is not that easy or quick. "Cliff failure is genuine; if a cliff is too tall, it will collapse, as everyone knows. How quickly that occurs is the question, according to Morlighem. However, we discovered that the rate of retreat is far lower than predicted by these preliminary simulations. We find that ice cliff instability never materializes when we employ a pace that is better limited by physics.

Thwaites Glacier was the focus of the researchers' attention since it has been noted as being particularly susceptible to collapse The scientists replicated the retreat of Thwaites for 50 years at the current rate of retreat as well as for 100 years after a dramatic, fictitious collapse of the ice shelf.

The researchers discovered that Thwaites' ice cliffs never moved inland at the rate that MICI predicted in all of their simulations. Instead, the ice sheet expands out from the interior as a result of the glacier's fast advance toward the ocean without the ice shelf to hold it back. The ice at the glacier's margin gets thinner due to this faster flow, which also lowers the ice cliffs' height and collapse risk.

"The standard, well-established projections that are the primary basis for the IPCC report are not being questioned," Seroussi stated. "All we are questioning is this low-likelihood, high-impact projection that incorporates this novel, poorly understood MICI method. In the ensuing decades and centuries, further known polar ice sheet instabilities will likely contribute to their melting.

For example, polar ice sheets are susceptible to the well-known Marine Ice Sheet Instability (MISI), according to research coauthor Dan Goldberg, an Edinburgh glaciologist who was a visiting professor at Dartmouth at the start of the project. According to MISI, a glacier resting on a submerged continent that slopes downward towards the heart of the ice sheet will recede unstably in the absence of ice shelves. According to Goldberg, this mechanism will likely hasten the melting of ice and increase the rate at which sea levels rise.

Goldberg stated, "While we did not observe MICI in the 21st century, this was partially due to processes that can lead to the MISI." "Either way, Thwaites is going to retreat unstably over the next few centuries, which emphasizes the need for continued modeling and observation to better understand the glacier's response to ocean warming and ice-shelf collapse."