Buried under the ice in West Antarctica was a long core of mud and rock containing shell fragments and remains of marine organisms that need sunlight to live. Those remains indicate that parts of the region once held open, sunlit water where thick ice now sits.
Below is a report on the team’s findings and published explanations, not an expert assessment of Antarctic ice stability or future sea-level rise.
What the drill actually pulled up
An international team drilled at Crary Ice Rise, a grounded ice dome at the inner margin of the Ross Ice Shelf. According to ETH Zurich, the crew used a hot-water drill to melt through 523 metres of ice, about 1,716 feet. They then drilled into the sediment beneath it, recovering a core of mud, gravel and rock 228 metres long, or 748 feet.
That length is a record. Co-chief scientist Molly Patterson of Binghamton University said, “To our knowledge, the longest sediment cores previously drilled under an ice sheet are less than ten metres. We exceeded our target of 200 metres. This is Antarctic frontier science.”
The tempting misread
Light-dependent organisms found beneath ice can sound like evidence of an emergency unfolding now. The core does not establish that. Think of it as a stack of layers laid down over a very long time. The remains record conditions from the past.
The finding addresses a different question: how this region behaved during earlier climates. Researchers have now refined the ages of the sediments, but the precise timing, duration and pace of past ice retreat still require detailed analysis.
What the light-loving organisms actually tell us
The value is in the variety. The team did not find one uniform story down the core. Patterson described the mix plainly: “We saw a lot of variability. Some of the sediment was typical of deposits that occur under an ice sheet like we have at Crary Ice Rise today.”
Other layers looked different. “But we also saw material that’s more typical of an open ocean, an ice shelf floating over ocean, or an ice-shelf margin with icebergs calving off,” she said.
A July 2026 update from the SWAIS2C project strengthened that interpretation. After splitting and examining the cores in New Zealand, researchers identified green mud rich in fossil diatoms—photosynthetic marine algae. The team described these layers as “a clear indication of an ice free open marine environment.”
Those findings support past Ross Ice Shelf collapse and West Antarctic Ice Sheet retreat. They do not yet establish a complete timeline of those changes.
Why a record of past ice-free conditions matters
Antarctica’s future in a warmer world is difficult to predict partly because direct geological records beneath its ice sheet are scarce. That is the gap this core is meant to help fill.
In February, co-chief scientist Huw Horgan said, “Initial indications are that the layers of sediment in the core span the past 23 million years, including time periods when Earth’s global average temperatures were significantly higher than 2°C above pre-industrial.”
That initial estimate has since changed. The July update reports that most of the core is now thought to be 7–10 million years old, with the bottom 20 metres dating to 17–19 million years ago. These remain preliminary estimates, refined using the diatom species present. Magnetic evidence preserved in the sediments will help improve the dating further.
The project brings together scientists from ten countries. The goal is to connect past ice conditions with past temperatures. “This record will give us critical insights about how the West Antarctic Ice Sheet and Ross Ice Shelf is likely to respond to temperatures above 2°C,” Horgan said.