An international team of researchers has recovered the longest sediment core ever drilled beneath an ice sheet, a scientific breakthrough for climate research. The 228-meter-long sample of mud and rock was extracted from beneath 523 meters of ice at the Crary Ice Rise on the edge of the West Antarctic Ice Sheet. The remote drilling site lies more than 700 kilometers from the nearest Antarctic research stations.
The core was obtained as part of the international SWAIS2C project (Sensitivity of the West Antarctic Ice Sheet to 2°C) and, according to initial analyses, reaches back up to 23 million years into the past. It contains a unique climate archive from earlier warm periods in Earth’s history, including phases when global average temperatures were well above 2°C above pre-industrial levels.
The West Antarctic Ice Sheet stores enough ice to raise global sea levels by 4 to 5 meters if it were to melt completely. Satellite measurements over recent decades already show accelerated mass loss. However, it has remained unclear how sensitive the ice sheet is to warming beyond 2°C. The new sediment core now provides the first direct geological evidence from the ice sheet’s own marginal zone, a crucial foundation for improving climate models.
Particularly revealing are discoveries of shell fragments and remains of light-dependent marine organisms. These findings demonstrate that open ocean once existed at this location, where today roughly 500 meters of ice covers the area. The evidence points to past retreat phases or possibly even partial collapse of the ice sheet. The detailed dating and analysis now underway aim to determine exactly when these phases occurred and what environmental conditions triggered them.
The 2025/26 expedition season posed enormous technical and logistical challenges. A 29-member team of scientists, engineers, and polar specialists lived for nearly ten weeks in a remote field camp on the ice. Using a hot-water drill, they first melted a 523-meter-deep borehole through the ice sheet. More than 1,300 meters of drill pipe were then deployed to reach the sediments below. Previous drilling attempts had failed due to technical difficulties, making this successful completion a major technological milestone in Antarctic research.
The sediment core has since been transported to Scott Base and will be shipped onward to New Zealand. From there, samples will be distributed to research institutions in the participating countries. The international team is already working to analyze the climate information preserved in the core.
The data obtained are expected to make a decisive contribution toward better estimating the future development of the West Antarctic Ice Sheet and the potential global sea-level rise under ongoing warming.
Heiner Kubny, PolarJournal