A newly developed computer model suggests that Antarctica’s massive Thwaites Glacier, widely referred to by scientists as the "Doomsday Glacier," could contribute far more significantly to global sea level rise than previous estimates indicated. Developed collaboratively by researchers at the University of California, Irvine (UCI), and NASA’s Jet Propulsion Laboratory (JPL), the advanced model predicts that melting from the colossal West Antarctic ice stream alone could raise global sea levels by as much as 30 millimeters by the year 2100.
That projected contribution is double earlier forecasts, and importantly, this accelerated melting could occur even without any additional warming of the global climate. The alarming findings were recently published in the scientific journal Nature Communications, shedding light on why conventional models have historically struggled to capture the true scale and speed of the glacier’s retreat.
For years, standard computer simulations treated the boundary between grounded ice resting on the bedrock and floating ice extending over the ocean as a narrow, sharply defined line. However, the new research accounts for a much broader area where warm ocean water can actively penetrate beneath the glacier. By incorporating this critical physical dynamic into their simulations, the research team successfully reproduced historical changes in the Thwaites Glacier from the 1990s to the present day that were four times more pronounced than the variations captured by traditional models.
Warm Ocean Water Is Melting Antarctica’s Ice From Below
To understand the shortcomings of earlier projections, the scientific team examined the fundamental assumptions that have long governed glaciology.
"Glaciologists have long based their assumptions of ice sheet dynamics on the ‘grounding line,’ a discreet, narrow and mostly stable demarcation where ice leaves the land and begins floating on water," said lead author Mattia Poinelli, who served as a UC Irvine postdoctoral scholar in Earth system science when the research was conducted. "We have come to acknowledge a different arrangement beneath Earth’s major ocean-terminating glaciers. Satellite observations demonstrate the existence of a ‘grounding zone,’ sometimes kilometers wide, where warm ocean water is reaching deep underneath the ice sheets and causing vigorous melting."
The Thwaites Glacier occupies a precarious and critical position in West Antarctica’s Amundsen Sea Embayment, a volatile region that is currently responsible for approximately one-third of the entire Antarctic Ice Sheet’s total mass loss. Over recent decades, satellite monitoring has confirmed that the glacier has grown notably thinner while retreating at an alarming pace. Furthermore, scientists have observed the ice flowing toward the ocean with increasing velocity, presenting a major puzzle because traditional computer models consistently failed to replicate the rapid acceleration detected from space.
To investigate and resolve this discrepancy, the UC Irvine-led research team meticulously compared their novel computer simulations with more than two decades of empirical observations. As part of this comprehensive analysis, the researchers examined high-resolution synthetic aperture radar measurements collected by Finland’s ICEYE satellite constellation. These advanced radar observations revealed dramatic physical fluctuations extending across several kilometers of the grounding zone located along the glacier’s main trunk.
The satellite evidence demonstrates that seawater travels several kilometers inland beneath ice that remains ostensibly grounded on the deep seafloor. As ocean tides rise and fall cyclically, this intruding water physically lifts the massive sheet of ice, repeatedly exposing its vulnerable underside to warm, pressurized seawater. This warm water is delivered to the Antarctic coastline through deep ocean currents that have been systematically altered by global climate change, thereby creating environmental conditions that aggressively accelerate melting from beneath the ice shelf.
Thwaites Glacier Could Lose a Critical Underwater Anchor
The implications of this extensive sub-glacial melting extend far beyond the immediate loss of ice volume. According to Poinelli, who is also a NASA JPL research affiliate and now works as a project scientist at UCLA, the movement of warm water beneath Thwaites is actively weakening its structural connection to underwater ridges that serve as natural anchors, keeping the glacier physically pinned in place. As these vital underwater supports progressively lose their grip, the overlying ice is able to flow outward with less resistance, allowing the glacier to retreat at an accelerated rate.
"The Thwaites main trunk is being temporarily stabilized by the Mouginot Ridge," Poinelli explained regarding the mechanics of the retreat. "Once that ridge is unpinned, the glacier will continually retreat across a predominantly retrograde seafloor toward its next topographic high, the South Ridge."
The research team’s simulations suggest that this critical structural tipping point could occur well before the end of the century. When the computer model incorporates a realistic grounding zone measuring between four and six kilometers across, it predicts a striking 60 percent probability that the Thwaites Glacier will become completely detached from the Mouginot Ridge by the year 2100.
"When you factor in key physical processes and calibrate against historical observations, you gain a reliable pathway for narrowing uncertainty in projections," Poinelli noted, emphasizing the rigorous methodology behind the new predictive tool.
New Model Points to Greater Coastal Flooding Risks
These updated projections indicate that the scientific community may have significantly underestimated the future contribution that the Thwaites Glacier will make to global sea level rise. By constructing a model that more accurately represents the complex physical interactions between warm ocean currents and the hidden undersides of polar ice sheets, the researchers have produced results that align much more closely with observed real-world changes, pointing directly toward substantially greater ice loss in the decades ahead.
"We have documented and quantified the impacts of climate change on our planet’s sensitive ice sheets for decades, but a mounting realization gained in recent years of what is happening on glaciers like Thwaites is leading to an even greater sense of alarm," said co-author Eric Rignot, a professor of Earth system science at UC Irvine.
Rignot pointed out that previous forecasting methods consistently struggled to match the observed rapidity of glacial mass loss because vital physical components were missing from the equations. The newly developed model, equipped with more comprehensive physics, successfully matches historical records and subsequently generates projections that are twice as large as earlier estimates. According to the researchers, these sobering results point directly to an elevated risk of severe coastal flooding and greater exposure for human populations worldwide in the decades to come.
