For months, the headline achievement of the SWAIS2C project was the remarkable drilling operation that recovered sediments from beneath more than 500 metres of ice at Crary Ice Rise in West Antarctica. Now, the first laboratory results are revealing why that core may become one of the most important climate archives yet recovered from the region.
Researchers examining the 228-metre sediment core have identified layers of distinctive green, diatom-rich mud. Diatoms are microscopic algae that thrive in sunlit ocean waters, and their presence suggests that the area was once an open marine environment rather than being permanently covered by an ice shelf.
What makes the discovery particularly significant is its location. The evidence points to ice-free conditions much closer to the centre of West Antarctica than scientists had previously documented. If confirmed through further analysis, the findings would provide direct evidence that the Ross Ice Shelf collapsed and parts of the West Antarctic Ice Sheet retreated during warmer periods in Earth's past.
The core appears to record a long history of environmental change. Preliminary estimates suggest that most of the recovered sediments were deposited between about 7 and 10 million years ago, while the deepest section may extend back as far as 17 to 19 million years.
Researchers are careful to emphasise that these results are still preliminary. The green sediments demonstrate the presence of open water, but they do not yet reveal the temperature conditions that produced the retreat of the ice sheet. Determining those thresholds is one of the next major goals of the project.
Samples are now being analysed by international teams using sedimentology, micropalaeontology, palaeomagnetism and geochemistry. Together, these studies will help reconstruct past Antarctic environments and improve the models used to predict future ice-sheet behaviour and global sea-level rise.
The drilling success made headlines. The climate history contained within the core may prove to be the bigger story.