Potential Irreversible Collapse of West Antarctic Ice Sheet Identified

A June 2025 modelling study indicates that the West Antarctic Ice Sheet (WAIS) could enter an irreversible collapse when deep-ocean temperatures around the Amundsen Sea rise by 0 °C to 0.25 °C above present levels. Once initiated, the collapse would be self-sustaining, eventually adding roughly four metres of sea-level rise over centuries to millennia.

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it begins

The authors identify marine ice sheet instability as the driver. WAIS rests on bedrock below sea level, with ice shelves buttressing grounded ice. Warm Circumpolar Deep Water undercuts the shelves, thinning them. Grounding-line retreat into deeper water reduces stability, enabling self-accelerating ice loss without additional warming.

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it begins

Using an 800 000-year model baseline, the authors—David Chandler, Petra Langebroek, Ronja Reese, Torsten Albrecht, Julius Garbe, and Ricarda Winkelmann—from the Potsdam Institute for Climate Impact Research, NORCE, and Northumbria University—note that their result is a single modelling outcome, not settled consensus. A 2023 study concluded WAIS had not yet crossed a tipping point, underscoring debate. Variations in ice physics, ocean forcing, and bedrock representation across models lead to differing thresholds.

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it begins

• Threshold: 0 °C–0.25 °C increase in deep-ocean temperature near the Amundsen Sea embayment.

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it begins

• Sea-level contribution: ~4 m at equilibrium, unfolding over centuries to millennia.

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it begins

• Timescales: destabilisation can trigger within decades; full ice-sheet growth needs tens of thousands of years.

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it begins

A four-metre sea-level rise would set a new equilibrium far beyond current infrastructure design lives, affecting coastlines worldwide. The rapid trigger versus prolonged consequence creates a “very long tail” that challenges conventional planning horizons.

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it begins

The International Thwaites Glacier Collaboration’s field campaigns aim to provide ground-truth data for model validation. Determining whether observed deep-ocean temperatures are approaching the 0.25 °C increment remains an open question that oceanographic records will address in coming years.

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it beginsNature

• “25°C threshold in the model, the process continues even if ocean temperatures were to stop rising.” — Study authors

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it begins

• “The four metres of sea-level rise is not a peak that would be reached and then reversed; it is the new equilibrium state the ice sheet would settle toward over the following centuries and millennia.” — Study authors

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it begins

• “25°C increment the study identifies, and how quickly, is a question the oceanographic record will continue to answer over the next several years.” — Study authors

Scientists say the West Antarctic Ice Sheet could collapse with very little additional warming and the four metres of sea level rise that would follow cannot be stopped once it begins