"Doomsday Glacier" melting much more aggressively - Sea level rise risk doubled by 2100

The planet's widest glacier is melting at a much more aggressive rate than predicted by previous scientific models, an event that could double its contribution to global sea level rise by the end of the century. According to new research by a team of glaciologists, the Thwaites Glacier in West Antarctica, also known as the "Doomsday Glacier", represents one of the largest wildcards in forecasts for future ocean level rise. Its moniker is tied to the potentially catastrophic consequences its collapse would entail. It is a glacier with an area comparable to Florida, situated in one of Earth's most inaccessible regions. Thwaites has been retreating for decades, with its melting ice currently contributing approximately 4% of global sea level rise. However, the mechanisms governing its retreat are exceptionally complex, making accurate predictions of its future trajectory difficult.

Why Thwaites provokes global concern

Monitoring this specific glacier is considered critical for understanding risks associated with climate change. If Thwaites were to collapse entirely, the volume of ice it holds could drive sea levels up by more than 2 feet, or roughly 61 centimeters. The danger, however, is not confined to the glacier itself. Thwaites acts like a natural cork holding back vast quantities of Antarctic ice. Should it lose stability, it could accelerate ice loss across the broader region, ultimately contributing to a long-term sea level rise of around 10 feet, or over 3 meters. Such an outcome would have devastating consequences for coastal communities and major cities worldwide, from Miami to Manila.

New scientific model reveals the glacier's weak spots

Scientists from the University of California, Irvine and NASA's Jet Propulsion Laboratory developed a new ice sheet model that they argue captures processes unfolding beneath the massive glacier with greater accuracy. Thwaites' rapid retreat is linked to dynamics at the "grounding line", the boundary where ice ceases to rest on the seafloor and begins floating on the ocean, forming an ice shelf. Traditional models often treated this line as a relatively static boundary. However, according to Mattia Poinelli, lead author of the study and UCLA scientist who conducted the research as an Earth system science researcher at the University of California, Irvine, scientists now recognize that different conditions prevail beneath major ocean-terminating glaciers. As he explained, the new data highlight a more intricate dynamic that can accelerate ice loss.

Seawater intrudes beneath the ice

Satellite data reveal that the grounding line is not actually a narrow, static line, but a broader "grounding zone" that can extend across several miles. In this zone, seawater continuously enters and recedes due to tides, causing the thick layer of ice to rise and settle. This process is known as "tidal pumping." According to Mattia Poinelli, this mechanism enables relatively warm seawater to penetrate deep beneath ice sheets, triggering intense melting. When scientists incorporated this process into their models, they found that Thwaites could contribute up to 1.2 inches, or about 3 centimeters, to sea level rise by 2100. This estimate is double previous forecasts and, according to findings published Monday in the scientific journal Nature Communications, occurs even without further increases in global temperatures.

Glacial retreat threatens to accelerate

An additional factor heightening scientist concern is the topography of the bedrock beneath the glacier. The bed on which Thwaites rests slopes downward toward greater depths. This means that as the glacier melts and retreats, increasingly larger volumes of ice are exposed to warm seawater, creating conditions that can further accelerate ice loss. The topography of the region, however, is complex, as two prominent subsea ridges anchor the glacier and limit the speed at which it flows toward the ocean. The new study finds that melting processes in the grounding zone are accelerating the detachment of ice from a major underwater ridge known as Mouginot Ridge. Researchers estimate there is a 60% probability that the glacier will detach from this ridge by the end of the century. Should this occur, Thwaites is likely to retreat rapidly along the sloping bedrock toward the next major ridge, a development that could further speed up ice loss.

Heightened risk for coastal regions

The new findings suggest that the impacts of ice loss at Thwaites may have been understated until now. A sea level rise of roughly 3 centimeters might appear modest. However, even such an increment can significantly exacerbate risks for coastal regions, particularly where flooding is already a severe problem. Eric Rignot, study co-author and professor of Earth system science at the University of California, Irvine, emphasized that the results herald greater danger and exposure to coastal flooding in coming decades than previously anticipated. This warning carries particular weight for regions with heavy concentrations of population, infrastructure, and economic activity near coastlines.

"Game changer" in sea level predictions

Ted Scambos, a senior research scientist at the Earth Science and Observation Center at the University of Colorado Boulder who was not involved in the study, described the findings as potentially decisive for forecasts regarding sea level rise driven by Thwaites. As he noted, the new approach could represent a true "game changer" in projecting the glacier's future evolution. However, he and other experts point out that additional research is required to clarify the precise impacts of different melting mechanisms within the grounding zone. Collecting direct measurements from the environment beneath the glacier is considered especially vital. Robert Larter, a marine geophysicist with the British Antarctic Survey who also was not involved in the study, warned that substantial knowledge gaps remain. "The reality is that we still have a lot to learn about processes in the grounding zone before we can make confident predictions about how fast ice will be lost," he stated. As he added, the environment beneath Thwaites is even more complex than described in the study, while access to the site remains extraordinarily difficult.

2028 mission for measurements beneath the glacier

The next step involves gathering direct observational data from Thwaites' grounding line. According to Eric Rignot, scientists plan to travel to the region in 2028 to deploy specialized instruments to record the intrusion and outflow of seawater beneath the ice. These measurements are expected to help researchers gain a better understanding of the processes driving rapid melt and refine predictive models for future ice loss. Eric Rignot underscored that scientists have known about the impacts of climate change on the planet's vulnerable ice sheets for decades. However, concern has intensified in recent years as researchers better comprehend what is occurring beneath glaciers like Thwaites.

The warning on climate change

Eric Rignot argued that the international community must immediately curtail planet-warming emissions to curb future impacts. At the same time, he warned that even with immediate action, sea level rise cannot be entirely avoided, as a portion of the consequences is tied to damage already done. The new study does not imply that Thwaites' collapse is certain or imminent. It demonstrates, however, that previous estimates may not have adequately captured the mechanisms accelerating its melt. The critical question for scientists now is how fast the glacier's retreat will continue and to what extent processes beneath the ice will accelerate sea level rise. The answers will shape planning for coastal defense and the assessment of climate-related risks worldwide.

www.bankingnews.gr