West Antarctica’s giant Thwaites Glacier and neighbouring ice streams repeatedly collapsed and retreated far inland during natural warm periods over the last 800,000 years, according to an international team of scientists.
Ocean Mud Reveals Ancient Ice Retreat
Researchers analyzing sediment cores drilled from 4,000 meters (13,000 feet) below the sea surface on Antarctica’s continental margin found that a distinctive mineral known as kaolinite vanished during every single interglacial period over the last 800,000 years.
Today, glaciers grind this china clay out of the bedrock, but the signal dropped to near-zero when marine ice melted and retreated.
Dr. Claus-Dieter Hillenbrand led the study published in Nature Communications (2026). The research, titled Repeated loss of the West Antarctic Ice Sheet’s Amundsen Sea sector during late Pleistocene interglacials, was provided by the British Antarctic Survey.
When the kaolinite signal at our drill-core sites suddenly collapses, it tells us the marine-based ice in the Amundsen Sea sector of the West Antarctic – including Thwaites and Pine Island glaciers – must have melted and retreated far back into the continent’s interior,
Hillenbrand said.
Currents Carry Distant Clays Southward
The research team identified a second clay mineral called smectite alongside the missing kaolinite. This particular magnesium-rich variety bears a distinct chemical profile native to the distant deep Pacific Ocean floor far northward, distinguishing it from local clays resulting from the weathering of Antarctic stone or volcanoes.
A mechanism was required to transport the smectite southward for deposition within near-shore muds—occurring precisely as the kaolinite vanishes, which is a vital detail.
The analysis involved examining shell-like structures that take different shapes depending on water temperature. Sedimentologists Anna Halberstadt and Claus-Dieter Hillenbrand examined a freshly split mud core, and the results of this analysis revealed a powerful regional thermal amplification.
Even when historical global mean temperatures during earlier warm epochs tracked only 1.0°C to 1.5°C above pre-industrial averages (comparable to modern times) or dropped below them, temperatures in the local waters bathing the front of the West Antarctic Ice Sheet rose to roughly 1°C to 3°C above the near-freezing baseline of today.
Greenhouse Gases Compress Collapse Timelines
The critical difference between past events and the current era is timescale. Under past natural conditions, Thwaites Glacier might have taken several thousand years to disappear. Human emissions of greenhouse gases are currently driving unprecedented ocean warming globally, creating the risk that this entire sequence could be compressed into a matter of centuries.
A complete collapse of Thwaites Glacier would raise global sea levels by 65 centimeters, while Pine Island could add another 51 centimeters. Wider areas of the West Antarctic Ice Sheet carry the potential to lift global levels by three to five meters.
I’m personally convinced that future generations will see substantial sea-level rise,
said Dr. Rob Larter, a BAS marine geophysicist and study co-author. How fast we’ll see that rise is really difficult to say. This study shows that even in past natural warm periods we had a lot of ice loss, but what we’re living in now is an interglacial on steroids.
How fast human emissions will compress centuries of natural melting into modern decades remains undetermined.