The 3,100 sq km (1,197 sq mile) Kestrel Ice Shelf disintegrated between 19 and 25 August, according to a study drawing on newly released satellite and ocean records. Researchers warn that the floating shelf had been holding back a much larger mass of grounded ice, and that its loss has already accelerated the glacier behind it.
The paper, published Tuesday in the journal Polar Systems Review, estimates that Kestrel Glacier could add 12cm to 18cm (4.7in to 7.1in) to global sea levels by 2100 under high-warming conditions. Its catchment holds enough ice for a rise of 74cm (29in) over the longer term, the authors say.
The findings were assembled using 23 years of radar and seabed observations made public under Australia’s Polar Data Access Act, which took effect on 1 July. The law requires publicly funded polar measurements to be released in a common archive, allowing researchers to compare records that had previously been difficult to combine.
The shelf’s final six days
Satellite records show fractures racing across the shelf before large sections broke away into the Southern Ocean. In the three weeks after the collapse, Kestrel’s grounded ice moved 31% faster, while its grounding line — the point where the glacier leaves land and floats — retreated 11km (7 miles), the study found.
Lead author Keits D. Liepiņa, a glaciologist at Hobart’s Southern Ice Dynamics Centre, said the result was not a prediction of a sudden global flood. But she warned that the new measurements overturn assumptions that the glacier would remain slow-moving through this century. “The shelf was the brake. It is gone, and the glacier is already responding,” she said.
The shelf was the brake. It is gone, and the glacier is already responding.
Keits D. Liepiņa, glaciologist
The study’s worst-case model puts Kestrel’s contribution at 18cm (7.1in) by 2100, compared with 4cm (1.6in) in earlier projections. Co-author Iker Figueroa said the figure depends on how quickly warm ocean water reaches the glacier’s underside and on future emissions. Even the lower estimate, he said, would add to sea-level rise from other ice sheets and expanding seawater.
Australia’s climate minister, Mary Holmes, said the paper did not mean coastal towns faced an immediate inundation threat. “There is no reason for people to change their plans this summer,” she said, while confirming that the government would review its Antarctic monitoring budget and coastal projections.
Data forces a new response
Liepiña said the reassurance was fair only in the narrow sense that the study predicts no sudden rise at Australian shorelines. “The danger is the speed of the change, not a wall of water next week,” she said. The paper estimates that a sustained acceleration could push sea levels higher for generations, increasing exposure for low-lying ports and suburbs.
The federal government is considering extra satellite passes and a research-vessel survey of the water beneath the remaining glacier tongue. Officials are also discussing whether Kestrel’s revised estimates should be added to coastal planning guidance due next year. The new law requires the underlying measurements to remain publicly accessible, giving other teams a chance to test the model.
The study’s authors say the next year is critical: fresh measurements will show whether the glacier’s faster flow is continuing or easing. For now, the shelf’s collapse has turned a distant Antarctic warning into a measurable change, with consequences that may build for decades before they reach shore.
