A bold revelation: scientists have drilled deeper into the West Antarctic Ice Sheet than ever before, turning back the clock to uncover evidence from millions of years ago that the region may have been open ocean at times. An international team of 29 researchers reports that the ice and underlying sediments reveal clues about how this vast ice mass behaved in the deep past.
The West Antarctic Ice Sheet is colossal and holds enough ice to lift global sea levels by about four to five metres (roughly 13 to 16 feet). By extracting cores through 523 metres of ice and 228 metres of ancient rock and mud from the Crary Ice Rise on the Ross Ice Shelf, scientists have obtained samples that illuminate conditions up to 23 million years ago.
The aim is to understand what triggered past melt events by examining ancient ocean temperatures and other environmental factors. By linking these historical conditions to the current trends of warming, researchers hope to better predict how quickly the ice sheet might shed mass in a warming climate.
“Satellite data over recent decades show accelerating ice loss, yet we still lack clarity on how much warming would drive rapid retreat,” the team said in a Wednesday report summarizing their early findings. “Until now, much of the ice-sheet modeling relied on geological records from distant regions.”
Scientists drilled through a substantial section of ice and into ancient sediments at Crary Ice Rise, a site of particular interest because it sits where the ice shelf is floating over ocean water. Co-chief scientist Molly Patterson of Binghamton University noted that while some sediment resembles deposits formed beneath today’s ice sheets, other fragments included shell pieces and remains of marine organisms that require light—evidence more typical of open-ocean conditions, or a floating ice shelf with calving margins.
This discovery reinforces the idea that parts of the Ross Sea region once connected with open ocean water and that the West Antarctic Ice Sheet may have undergone significant retreat or collapse in the past. Yet the timing of those events remained uncertain until now. The new core records provide a sequence of environmental conditions through time and direct proof that open-ocean conditions existed in this locale.
Huw Horgan, co-chief scientist from Victoria University of Wellington, indicated that the initial results suggest the sampled interval spans the last 23 million years, encompassing eras when Earth’s average global temperatures were markedly higher than pre-industrial levels by more than two degrees Celsius.
Drilling concluded in January, and the core samples were transported more than 1,100 kilometres (about 680 miles) across the Ross Ice Shelf to Scott Base. They will then be sent to New Zealand for further analysis and interpretation.
