By Rachel Duckett,
Dec. 20, 2025
Columbia University researchers are using grains of sediment left behind on the ocean floor millions of years ago to track the movement of icebergs through the Southern Ocean’s “Iceberg Alley,” just east of the Drake Passage between the southern tip of South America and Antarctica.
As icebergs broke off the Antarctic ice sheet and traveled along the alley, they left trails of sediment crumbs in their wake. Through these crumbs, Columbia University researcher Claire Jasper found patterns of iceberg flux that suggest changes in ice sheet stability during a climactic shift called the mid-Brunhes event, around 430,000 years ago, when global temperatures, CO2 levels and sea level rise increased. The findings are crucial because the increases then were fairly minor compared to the accelerating rate of climate change due to fossil fuel emissions over the past several decades.
Jasper, a Ph.D. candidate at Columbia University’s Lamont-Doherty Earth Observatory, used artificial intelligence to identify debris in X-rays of ocean sediment samples and looked at physical samples to figure out the origins of the icebergs that carried the sediment. What she found was a cohesive signal of iceberg discharge from sites hundreds of miles apart.
“Because of the AI method, we could identify iceberg rafting at multiple sites,” she said. “The sites look the same. So that was the super cool thing. These sites are tens, if not hundreds, of miles away from each other, and they’re showing a similar record.”
That finding adds to a long line of research using ocean sediment cores that has expanded our understanding of Earth’s history.
“The things where our research now interacts with the wider world are on sea level rise and that’s especially an issue with Antarctica and that’s especially an issue with how it interacts with the ocean,” said Richard Alley, a prominent climate change scientist, author and professor at Penn State University, at this year’s Comer Climate Conference in Wisconsin.
“So this history of what’s been happening in the ocean off of Antarctica and the understanding of how the ocean works are fitting together into, I think, leading us to better projections of what might happen in the future,” Alley said.
The cores that Jasper and many other climate researchers use were gathered using methods similar to deep sea oil exploration. Instead of drilling for oil, they extract sediment cores in tubes of mud and rock from the ocean floor.
“We actually use a piston, but since it’s soft mud at the top, you just puncture the mud and then pull it back up, puncture the mud and pull it back up using some pressure. But eventually it’s hard enough that then you have to drill,” Jasper said.
For Jasper’s research, the samples she used from cores taken in and around Antarctica date back about 3 million years. But ocean drilling is able to unearth samples much older than that and researchers have studied sediment as old as 170 million years old. To put that in perspective, the dinosaurs became extinct about 65 million years ago.
Since 1985, the U.S. has relied primarily on one ship for scientific ocean drilling: the JOIDES Resolution. The ship was part of the International Ocean Discovery Program and was funded by the National Science Foundation (NSF).
“I think a lot of people don’t realize just how much about earth we’ve learned from the ocean floor,” said Maya Pincus, science communications officer for the International Ocean Discovery Program.
That includes confirmation of plate tectonics theory, plus elements and organisms preserved in ocean sediment that can act as a record of the earth’s climate and how it’s changed.
But in 2023, the NSF announced that it would not renew its agreement with Texas A&M University to fund operations and maintenance for the ship. In the summer of 2024, the JOIDES Resolution took its final voyage.
“NSF will continue to support the U.S. scientific ocean drilling community through investments in research utilizing existing samples and data and will work with the research community to plan for the future of scientific ocean drilling,” the NSF stated in a media release.
Even though the JOIDES Resolution is out of commission, researchers, including Jasper, will still be able to use existing samples extracted on past voyages and preserved at one of three core repositories around the world to unravel more of Earth’s secrets, at least for now.
“If there’s a science question that can be asked, it can probably be answered by studying the ocean floor,” Pincus said.
Photo at top: Columbia University scientist Claire Jasper drills cores of ancient sediments from the ocean floor to reveal clues to climate change as part of a research expedition on the JOIDES Resolution in 2023. (Credit: Tiffany Liao, IODP JRSO/Courtesy of Claire Jasper)