Rosie Williams says the doomsday glacier still loses ice in a model world where ocean-driven melting is switched off. Thwaites Glacier, the world’s widest glacier in Antarctica, kept retreating for at least 150 years in three different computer models.
Williams called the setup "did something quite wild". She added, "But with Thwaites glacier, we found something really different" and said, "Our general expectation was …that if you turned off that ocean melting, the ice would be able to thicken and re-advance. It’s somewhat of a surprise that Thwaites glacier can’t do that."
British Antarctic Survey model results
The British Antarctic Survey researcher said the ice still loses mass under the zero-melt scenario, but faster ocean warming still speeds the loss. "Under the zero-melt scenario, [Thwaites glacier] still loses ice, but the more warming you have in the ocean, the faster that ice is lost, so it’s still really essential to bring down our emissions and control that rate of ice loss," Williams said.
Pine Island Glacier behaved differently. It re-advanced and became more stable in the same simulations, while Thwaites Glacier kept losing ice over the full 150 years. That split response is what makes the result stand out: the same change in ocean forcing did not produce the same response from the two glaciers.
Ted Scambos on instability
Ted Scambos of the University of Colorado Boulder said, "Ocean heat delivered to the base of the ice ….over the past four decades or so, as a result of anthropogenic warming, has pushed the Thwaites system into an inherently unstable configuration," and Williams said, "We’re still seeing some effect of that playing out today with Thwaites. [Glaciers] are really slow-moving. They have a long memory," The researchers think extreme El Niño conditions in the 1940s may still be affecting Thwaites Glacier today.
Thwaites Glacier is roughly the size of Great Britain and is already collapsing at an alarming rate due to ocean warming. If Thwaites Glacier collapses completely, it could help drive more widespread loss of West Antarctic ice and about 5 metres of sea-level rise. The models now suggest that even a sharp cut in ocean melting would not stop the glacier from losing ice for generations.
West Antarctica sea-level risk
The practical takeaway is narrow but important: slowing ocean warming still changes the pace of loss, even if it does not reverse the glacier’s current path in these simulations. Williams summed it up with a direct answer to the mitigation question: "Almost the opposite," because the glacier still loses ice, just more slowly when the ocean warms less.
What the study has not pinned down is the exact mechanism keeping Thwaites Glacier from thickening and re-advancing after ocean melting is removed. That is the piece researchers will keep testing, because the glacier’s behavior today still points to a system that has already been pushed out of balance.
