Thwaites Glacier could rival entire Antarctic ice loss

 Models warn Thwaites Glacier may match all Antarctic ice loss by 2067

New research warns Thwaites Glacier in West Antarctica could lose 180–200 gigatonnes of ice annually by 2067, rivaling the continent’s current total ice loss. The projection, based on satellite-calibrated models, underscores the glacier’s accelerating instability and its potential to sharply raise global sea levels. Scientists stress improved observation and model calibration are critical to refining future predictions. Thwaites Glacier is currently losing ice five times faster than in the 1990s. The future of one of Antarctica's most iconic glaciers could be far more dramatic than scientists previously thought. Using satellite calibrated ice sheet models, a team of researchers from the University of Edinburgh revealed this. This would represent a stunning acceleration in ice loss from a single glacier and underlines urgent concerns about future contributions to sea level rise. Thwaites Glacier is already one of the fastest changing and most closely watched glaciers on Earth. It drains a huge area of the West Antarctic Ice Sheet and outlets into the Amundsen Sea. In recent decades, observations from satellites have shown that it has been thinning and accelerating, losing more ice to the ocean than it gains from snowfall. This imbalance is what drives its contribution to global sea level rise.

Understanding how much ice could be lost in the coming decades is not just a matter of measuring what's happening now. Scientists rely on computer models which simulate the physics of ice flow, ocean melting, and changing surface conditions, but those models need to be calibrated against real observations, in this case, data on how fast the glacier surface is lowering and how the ice is moving. The findings show that model calibration choices, especially using surface elevation change data, strongly influence future loss projections. Why does this matter to people far from the poles? Because ice that melts into the ocean raises global sea levels. Even if Thwaites Glacier were to continue shedding ice at "only" current rates, tens of billions of metric tons/year, it contributes measurably to rising sea levels. If the rate climbs toward the 180–200 gigatonne range, the glacier's contribution could accelerate faster than many global projections assume. For context, the Antarctic ice sheet has been losing roughly 135–150 gigatonnes of ice/year over the past two decades. Sea level rise may seem abstract, but its impacts are concrete. Even a few tens of centimeters of additional sea level rise can worsen coastal flooding, intensify storm surges and alter shoreline ecosystems. Scientists estimate that Thwaites Glacier alone holds enough ice to raise global sea levels by about 65 cm if it were to fully collapse, an amount that could reshape coastlines and threaten low-lying cities if spread over coming centuries.

Scientists report Antarctica is undergoing 'Greenlandification,' with rapid surface melt, ice shelf loss, and grounding line retreat resembling Greenland's patterns. West Antarctica’s Amundsen Sea Embayment, home to Thwaites, has seen ice flow accelerate by 50% since the 1990s. Loss of ice shelves removes vital buttressing, exposing outlet glaciers to faster retreat, amplifying the risk of large-scale ice loss. The new findings do not mean that Thwaites Glacier will hit a catastrophic loss rate exactly by 2067 as models represent a range of possibilities, and future climate conditions and ocean warming will shape actual outcomes. But they do show that if current trends continue and specific model assumptions hold, the glacier's mass loss could accelerate sharply within a few decades. Scientists emphasize that getting the model calibration right matters, because it helps ensure projections of future sea level rise are grounded in what the ice sheet is actually doing now. One of the key findings of the new study is that the way models are "trained" against observations strongly influences their long-term predictions. Models that were constrained using satellite measurements of surface elevation change (how the height of the glacier is decreasing over time) projected the largest future mass losses. Those projections suggest that by 2067, the rate of ice loss from Thwaites Glacier could equal what the entire Antarctic ice sheet currently contributes to sea level rise each year.

By contrast, calibrating models using only ice velocity data (how fast ice is moving toward the ocean) produced lower and more stable future loss rates. This discrepancy shows that what data scientists choose to emphasize when calibrating models can dramatically change the future picture scientists paint for Thwaites Glacier. While both approaches capture important behaviors, the models incorporating surface elevation changes appear to match the recent observed patterns of thinning most consistently. Even at current loss rates, Thwaites Glacier measurably contributes to sea level rise; at projected rates, impacts could outpace many global forecasts. Scientists warn that marine ice sheet instability and focused inland thinning along deep troughs could accelerate retreat. Another important detail from the research is where the thinning is happening. The models show focused patterns of ice thinning spreading inland along deep troughs beneath the glacier, potentially indicating areas which are particularly vulnerable to continued melt and retreat. These deep troughs are a hallmark of what scientists call marine ice sheet instability, a process where a glacier resting on a bed which slopes downward inland can become harder to slow once melt and retreat begin.

A British Antarctic Survey and Korea Polar Research Institute team drilled deep into Thwaites Glacier, capturing striking images of layered ice and subglacial caves. The attempt, hindered by shifting ice and severe weather, aimed to deploy instruments to study warm water melting the glacier from below. Although the mission was cut short, researchers say the site is crucial for understanding ice-ocean interactions driving ice loss. One of the lessons from this study is that better observations lead to better models. As satellites continue to collect data on surface elevation, ice flow speed and grounding line retreat (the point where grounded ice lifts off the bed and begins to float), scientists will be able to refine models and reduce uncertainties. Grounding lines are particularly important because changes there can herald rapid phases of retreat. Researchers also stress the need to understand how the ocean interacts with the ice from below, warm water circulating beneath the floating ice shelves can melt ice from the underside and weaken the glacier's grip on the bedrock. This ocean-ice interaction is a key driver of current changes in the Amundsen Sea sector, where Thwaites Glacier sits. Observations of water properties and ice-ocean contact zones are already helping to improve model physics.

In the years to come, sea level rise projections will likely continue to evolve as models incorporate more detailed physics and more comprehensive observational constraints. But the central message from the new study is clear: Thwaites Glacier's future could be more dynamic and impactful than previously thought, and the way scientists calibrate models matters for understanding that future. Researchers stress that better observations of surface elevation, ice velocity, grounding lines and sub-ice ocean conditions are essential to improve accuracy. Ocean-ice interactions, including warm water melting from below and hydrofracturing from above, remain difficult to model yet critical to understanding future ice loss. Enhanced data will help reduce uncertainties and guide policy responses to rising sea levels of the world.