Climate scientists drilled 500 feet into an ice floe on the Antarctic ocean floor and retrieved a rare record of 23 million years of sediment. This record helps prove why Antarctica’s southern ice shield determines the fate of remote, low-lying coastal areas.
Layers of rock, silt, and fossils are like pages from a book of geological time, revealing how West Antarctica’s vast ice sheets and floating shelves responded rapidly to modest warming, with significant shrinkage and melting in a climate similar to today.
Together with other new modeling studies and analyzes of current ice retreat, the marine sediment core samples confirm that human-induced warming is causing an irreversible long-term meltdown that could submerge the southern third of Florida and other low-lying coastal areas within a few centuries.
A growing body of evidence from paleoclimatology, modeling and observations is also converging to suggest that global average sea level rise will accelerate in the near future, reaching 3 feet by the end of the century and up to 5 feet in equatorial island regions, potentially displacing millions of people around the world.
The groundbreaking drilling expedition at the remote tip of the Ross Ice Shelf is part of a broader effort “to answer the questions of when and under what conditions the West Antarctic ice sheet disappears,” said Johann Klages, a geoscientist at the Alfred Wegener Institute in Germany and co-coordinator of the international SWAIS2C project, which assesses West Antarctica’s vulnerability to 2 degrees Celsius (3.6 degrees Celsius). Fahrenheit) is the degree of anthropogenic warming above pre-fossil fuel era baselines.
The world could reach that level sooner than expected by 2050, according to a recent warning from former NASA climatologist James Hansen. And how that level of warming would affect Antarctica’s vast ice fields is exactly the question the 29-member ice core team set out to answer as they set up camp for 10 weeks. Their equipment had to be transported by motorized vehicle over 600 miles of ice.
Previous attempts to drill beneath the ice have failed due to technical and logistical challenges, but this time the mission was successful thanks to significant technical support from the U.S. Antarctic Program and the National Science Foundation.
Binghamton University associate professor Molly Patterson, co-principal scientist of the SWAIS2C mission, said the core’s sediment layers show how the ice advanced and retreated, but determining the exact timing will require detailed geochemical analysis, which could take years to complete.
The sediment core is more than 200 meters deep, an unusual depth compared to previous subglacial sediment cores that rarely exceeded 10 meters, and provides a continuous record of climate conditions spanning epochal fluctuations between ice ages and warm interglacial periods.
Recent studies at Thwaites Glacier, the Ross Ice Shelf, and other parts of Antarctica follow mixed evidence and come to the same stark conclusion: massive glacier melt and sea level rise are ahead. Credit: NOAA
Reading the core is like reconstructing a past environment layer by layer, Patterson says. When the ice comes into contact with the ocean floor, it “crushes everything” and leaves behind coarsely mixed debris. But layers of fine mud studded with large stones that have fallen from melting ice shelves suggest that the ice is floating. And if those layers contain fossils of light-dependent organisms like plankton, it indicates an ice-free open body of water. In addition to chemical analysis to determine the age of the material, scientists can learn where the edge of the ice was and what the sea temperature was at the time.
There have been other sediment samples taken from near the edge of Antarctica, but no sediment cores as deep as this have been taken from inside the ice sheet, said Ed Gasson, a glaciologist and associate professor at the University of Exeter in the UK and a member of the SWAIS2C team.
“This is important,” Gasson said. “Because it speaks directly to the fact that this part of the ice sheet, which we think is particularly vulnerable to a warming climate, has retreated in the geological past, leaving open ocean water behind.”
climate dominoes falling
Two other studies published last month further raise concerns about the potential vulnerability of Antarctic ice. A research team has mapped how Antarctic ice flows through interconnected basins, showing how melting in one region destabilizes others and accelerates ice loss and sea level rise. A separate analysis based on measurements from West Antarctica’s Thwaites Glacier tested the model’s accuracy and showed that the current rate of ice loss is consistent with long-term predictions of significant melting.
Sediment records show what happened yesterday, and observations of Thwaites Glacier provide information about recent melting. But the big question is what will happen tomorrow, said Jonathan Donges, an Earth system researcher at Germany’s Potsdam Institute for Climate Impact Research and co-author of a paper examining the dynamic connections between the continent’s vast ice regions.
This story is funded by readers like you.
Our nonprofit newsroom provides free advertising for our award-winning climate coverage. We rely on donations from readers like you to continue our work. Donate now to support our work.
donate now
By mapping how ice basins interact, the researchers showed that melting in one region can spread and destabilize other regions, potentially pushing the entire system past a critical threshold that halts sea level rise over millennia.
Donges said such long timescales are often overlooked, even if the effects are severe. He added that while people tend to focus on what will happen by 2100, the real story is that we are set in motion over the next few decades and that will unfold over the next centuries. His team looked at how ice basins interact with each other, since previous research had shown that different regions have different thresholds for significant melting. Losing even one basin could cause sea levels to rise by 20 or 30 feet.
The Amundsen Sea region of West Antarctica has already been identified as one of the most vulnerable regions to current levels of warming, he said, adding that even if global temperatures stabilize, its ice will continue to retreat for centuries.
As the ice thins and retreats, the ice-ocean-rock interface retreats inland, exposing more open ocean and accelerating further melting. Over time, that retreat spreads inland, altering ice flows and destabilizing adjacent basins in cascading processes that melt deep into the continent.
A new paper on Thwaites Glacier points out that the ice is flowing faster, thinning at the glacier’s edges, increasing structural weakness and receding the grounding line that anchors the ice to the ocean floor.
The amount of ice flowing from Antarctic glaciers has doubled in the last 30 years, and scientists believe even more dramatic changes could occur in the near future. Credit: NASA Earth Observatory
All the findings strengthen scientific understanding that once a significant portion of an ice sheet begins to weaken, feedback processes can take over and retreat can continue long after the initial warming.
Donges said even the conservative estimate of about 13 feet of sea level rise by 2300 seems huge.
“When you’re standing on a beach somewhere, it’s hard to imagine that this could happen over the course of America’s existence,” he says.
And it could get even worse. Donzis said projections of sea level rise of this magnitude do not include rapid and large-scale collapse of ice shelves, explaining that some studies suggest feedbacks could cause large ice regions to collapse sooner than expected.
With extreme warming and surface melting, meltwater “flows into deep cracks and then refreezes, widening the cracks,” he said. “This could cause the ice sheet to fracture and break up more quickly.”
About this story
As you may have noticed, this article, like all news we publish, is free to read. That’s because Inside Climate News is a 501c3 nonprofit organization. We don’t charge subscription fees, keep our news behind paywalls, or fill our website with ads. We provide climate and environmental news free to you and anyone who wants it.
That’s not all. We also share our news for free with dozens of other news organizations across the country. Many of them cannot afford to do their own environmental journalism. We’ve established bureaus across the country to report on local news, partner with local newsrooms and co-publish stories to ensure this important work is shared as widely as possible.
The two of us started ICN in 2007. Six years later, we won the Pulitzer Prize for national reporting and now run the nation’s oldest and largest dedicated climate newsroom. We tell the story in its entirety. We hold polluters accountable. We expose environmental injustice. We debunk misinformation. We explore solutions and inspire action.
Donations from readers like you fund all aspects of our work. If you haven’t already, will you support our ongoing work, our coverage of the biggest crises facing our planet, and help us reach more readers in more places?
Please make a tax-deductible donation. Each one makes a difference.
thank you,
bob berwin
reporter, austria
Bob Barwin is an Austria-based reporter who has covered climate science and international climate policy for more than a decade. Previously, he reported on the environment, endangered species, and public lands for several Colorado newspapers, and also worked as editor and associate editor for a community newspaper in the Colorado Rockies.
