The ice told a story of Earth's climate history. The frozen soil was examined, set aside and then forgotten.
Half a century later, scientists rediscovered that soil in a Danish freezer. It is now revealing its secrets.
Using lab techniques unimaginable in the 1960s when the core was drilled, we and an international team of fellow scientists were able to show that Greenland's massive ice sheet had melted to the ground there within the past million years. Radiocarbon dating shows that it would have happened more than 50,000 years ago. It most likely happened during times when the climate was warm and sea level was high, possibly 400,000 years ago.
And there was more. As we explored the soil under a microscope, we were stunned to discover the remnants of a tundra ecosystem – twigs, leaves and moss. We were looking at northern Greenland as it existed the last time the region was ice-free. Our peer-reviewed study was published on March 15 in Proceedings of the National Academy of Sciences.
Engineers pull up a section of the 4,560-foot-long ice core at Camp Century in the 1960s. U.S. Army Corps of Engineers
With no ice sheet, sunlight would have warmed the soil enough for tundra vegetation to cover the landscape. The oceans around the globe would have been more than 10 feet higher, and maybe even 20 feet. The land on which Boston, London and Shanghai sit today would have been under the ocean waves.
All of this happened before humans began warming Earth's climate. The atmosphere at that time contained far less carbon dioxide than it does today, and it wasn't rising as quickly. The ice core and the soil below are something of a Rosetta Stone for understanding how durable the Greenland ice sheet has been during past warm periods – and how quickly it might melt again as the climate heats up.
Secret Military Bases and Danish Freezers
The story of the ice core begins during the Cold War with a military mission dubbed Project Iceworm. Starting around 1959, the U.S. Army hauled hundreds of soldiers, heavy equipment and even a nuclear reactor across the ice sheet in northwest Greenland and dug a base of tunnels inside the ice. They called it Camp Century.
It was part of a secret plan to hide nuclear weapons from the Soviets. The public knew it as an Arctic research laboratory. Walter Cronkite even paid a visit and filed a report.
Workers build the snow tunnels at the Camp Century research base in 1960. U.S. Army Corps of Engineers
Camp Century didn't last long. The snow and ice began slowly crushing the buildings inside the tunnels below, forcing the military to abandon it in 1966. During its short life, however, scientists were able to extract the ice core and begin analyzing Greenland's climate history. As ice builds up year by year, it captures layers of volcanic ash and changes in precipitation over time, and it traps air bubbles that reveal the past composition of the atmosphere.
One of the original scientists, glaciologist Chester Langway, kept the core and soil samples frozen at the University at Buffalo for years, then he shipped them to a Danish archive in the 1990s, where the soil was soon forgotten.
A few years ago, our Danish colleagues found the soil samples in a box of glass cookie jars with faded labels: "Camp Century Sub-Ice."
Geomorphologist Paul Bierman (right) and geochemist Joerg Schaefer of Columbia University examine the jars holding Camp Century sediment for the first time. They were in a Danish freezer set at -17 F. Paul Bierman / CC BY-ND
A Surprise Under the Microscope
On a hot July day in 2019, two samples of soil arrived at our lab at the University of Vermont frozen solid. We began the painstaking process of splitting the precious few ounces of frozen mud and sand for different analyses.
First, we photographed the layering in the soil before it was lost forever. Then we chiseled off small bits to examine under the microscope. We melted the rest and saved the ancient water.
Then came the biggest surprise. While we were washing the soil, we spotted something floating in the rinse water. Paul grabbed a pipette and some filter paper, Drew grabbed tweezers and turned on the microscope. We were absolutely stunned as we looked down the eyepiece.
Staring back at us were leaves, twigs and mosses. This wasn't just soil. This was an ancient ecosystem perfectly preserved in Greenland's natural deep freeze.
Dating Million-Year-Old Moss
How old were these plants?
Over the last million years, Earth's climate was punctuated by relatively short warm periods, typically lasting about 10,000 years, called interglacials, when there was less ice at the poles and sea level was higher. The Greenland ice sheet survived through all of human history during the Holocene, the present interglacial period of the last 12,000 years, and most of the interglacials in the last million years.
But our research shows that at least one of these interglacial periods was warm enough for a long enough period of time to melt large portions of the Greenland ice sheet, allowing a tundra ecosystem to emerge in northwestern Greenland.
We used two techniques to determine the age of the soil and the plants. First, we used clean room chemistry and a particle accelerator to count atoms that form in rocks and sediment when exposed to natural radiation that bombards Earth. Then, a colleague used an ultra-sensitive method for measuring light emitted from grains of sand to determine the last time they were exposed to sunlight.
Maps of Greenland show the speed of the ice sheet as it flows (left) and the landscape hidden beneath it (right). BedMachine v3; Copernicus Climate Change Service (C3S) / CC BY-ND
The concentration of carbon dioxide in the atmosphere today is well beyond past levels determined from ice cores. On March 14, 2021, the CO2 level was about 417 ppm. NASA Jet Propulsion Laboratory / CC BY-ND
The million-year time frame is important. Previous work on another ice core, GISP2, extracted from central Greenland in the 1990s, showed that the ice had also been absent there within the last million years, perhaps about 400,000 years ago.
Losing the Greenland ice sheet would be catastrophic to humanity today. The melted ice would raise sea level by more than 20 feet. That would redraw coastlines worldwide.
About 40% of the global population lives within 60 miles of a coast, and 600 million people live within 30 feet of sea level. If warming continues, ice melt from Greenland and Antarctica will pour more water into the oceans. Communities will be forced to relocate, climate refugees will become more common, and costly infrastructure will be abandoned. Already, sea level rise has amplified flooding from coastal storms, causing hundreds of billions of dollars of damage every year.
Tundra near the Greenland ice sheet today. Is this what Camp Century looked like before the ice came back sometime in the last million years? Paul Bierman / CC BY-ND
The story of Camp Century spans two critical moments in modern history. An Arctic military base built in response to the existential threat of nuclear war inadvertently led us to discover another threat from ice cores – the threat of sea level rise from human-caused climate change. Now, its legacy is helping scientists understand how Earth responds to a changing climate.
Andrew Christ is a postdoctoral fellow and lecturer in geology at the University of Vermont.
Paul Bierman is a fellow of the Gund Institute for Environment and professor of geology and natural resources at the University of Vermont.
Disclosure statement: Andrew Christ receives funding from the Gund Institute for Environment and the National Science Foundation. Paul Bierman receives funding from the U.S. National Science Foundation and UVM Gund Institute for Environment.
Reposted with permission from The Conversation.
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Eye-Catching Designs Made from Recycled Plastic Bottles
The company sells a range of eco-friendly items like leggings, rash guards, and board shorts that are made using recycled post-consumer plastic bottles. There are currently 16 causes represented by distinct marine-life patterns, from whale shark research and invasive lionfish removal to sockeye salmon monitoring and abalone restoration.
One such organization is Get Inspired, a nonprofit that specializes in ocean restoration and environmental education. Get Inspired founder, marine biologist Nancy Caruso, says supporting on-the-ground efforts is one thing that sets Waterlust apart, like their apparel line that supports Get Inspired abalone restoration programs.
"All of us [conservation partners] are doing something," Caruso said. "We're not putting up exhibits and talking about it — although that is important — we're in the field."
Waterlust not only helps its conservation partners financially so they can continue their important work. It also helps them get the word out about what they're doing, whether that's through social media spotlights, photo and video projects, or the informative note card that comes with each piece of apparel.
"They're doing their part for sure, pushing the information out across all of their channels, and I think that's what makes them so interesting," Caruso said.
And then there are the clothes, which speak for themselves.
Advocate Apparel to Start Conversations About Conservation
Waterlust's concept of "advocate apparel" encourages people to see getting dressed every day as an opportunity to not only express their individuality and style, but also to advance the conversation around marine science. By infusing science into clothing, people can visually represent species and ecosystems in need of advocacy — something that, more often than not, leads to a teaching moment.
"When people wear Waterlust gear, it's just a matter of time before somebody asks them about the bright, funky designs," said Waterlust's CEO, Patrick Rynne. "That moment is incredibly special, because it creates an intimate opportunity for the wearer to share what they've learned with another."
The idea for the company came to Rynne when he was a Ph.D. student in marine science.
"I was surrounded by incredible people that were discovering fascinating things but noticed that often their work wasn't reaching the general public in creative and engaging ways," he said. "That seemed like a missed opportunity with big implications."
Waterlust initially focused on conventional media, like film and photography, to promote ocean science, but the team quickly realized engagement on social media didn't translate to action or even knowledge sharing offscreen.
Rynne also saw the "in one ear, out the other" issue in the classroom — if students didn't repeatedly engage with the topics they learned, they'd quickly forget them.
"We decided that if we truly wanted to achieve our goal of bringing science into people's lives and have it stick, it would need to be through a process that is frequently repeated, fun, and functional," Rynne said. "That's when we thought about clothing."
Support Marine Research and Sustainability in Style
To date, Waterlust has sold tens of thousands of pieces of apparel in over 100 countries, and the interactions its products have sparked have had clear implications for furthering science communication.
For Caruso alone, it's led to opportunities to share her abalone restoration methods with communities far and wide.
"It moves my small little world of what I'm doing here in Orange County, California, across the entire globe," she said. "That's one of the beautiful things about our partnership."
Check out all of the different eco-conscious apparel options available from Waterlust to help promote ocean conservation.
Melissa Smith is an avid writer, scuba diver, backpacker, and all-around outdoor enthusiast. She graduated from the University of Florida with degrees in journalism and sustainable studies. Before joining EcoWatch, Melissa worked as the managing editor of Scuba Diving magazine and the communications manager of The Ocean Agency, a non-profit that's featured in the Emmy award-winning documentary Chasing Coral.
While the figures themselves are consistent with other studies, as The New York Times pointed out, the satellite laser allows researchers a much more precise picture of how polar ice is changing over time, which helps determine the role of the climate crisis and plan for future sea level rise.
"We've all been waiting for this new dataset," Lamont-Doherty Earth Observatory research professor Robin Bell told NPR.
The study, published in Science Thursday, combines data from two NASA satellites: the original Ice, Cloud and land Elevation Satellite (ICESat), which took measurements from 2003 to 2009, and ICESat-2, launched in 2018. The two satellites allowed researchers to measure changes in ice mass from 2003 to 2019, and to calculate that Greenland and Antarctica contributed 0.55 inches to sea level rise during that time. That's around a third of the global total, which was also driven by the expansion of oceans as they warm, NPR explained.
"If you watch a glacier or ice sheet for a month, or a year, you're not going to learn much about what the climate is doing to it," University of Washington glaciologist and lead study author Ben Smith said in a NASA press release. "We now have a 16-year span between ICESat and ICESat-2 and can be much more confident that the changes we're seeing in the ice have to do with the long-term changes in the climate."
The data also revealed that Greenland's ice sheet lost an average of 200 gigatons of ice per year and Antarctica's lost an average of 118. That's more than 5,000 gigatons total, NPR reported. To put that in perspective, one gigaton is enough to fill 400,000 Olympic-sized swimming pools.
But the satellite data also helped show how the ice was being lost. In Antarctica, the East actually gained mass, probably because of increased precipitation, The New York Times reported. But this was offset by losses in West Antarctica and the Antarctic Peninsula. In West Antarctica, 30 percent of that loss was due to floating ice, which either calves icebergs or melts from below due to warm ocean water. While this ice cannot contribute directly to sea level rise because it is already floating, its loss destabilizes the so-called "grounded ice" that can.
"It's like an apple tart and the ice shelves are like the wall of pastry around the edges of the tart," Scripps Institution of Oceanography at the University of California-San Diego glaciologist and study coauthor Helen Fricker explained to NPR. "And if those walls are too thin or they're not baked well enough, then the filling will ooze out."
In Greenland, two thirds of the ice loss was due to surface melting, something that rarely occurs in Antarctica, The New York Times said. Greenland also lost a lot of mass from its coastal glaciers, according to NASA. Its Kangerdulgssuaq and Jakobshavn glaciers have shrunken by 14 to 20 feet per year.
NASA explained why its satellites were able to provide such a detailed portrait:
ICESat-2's instrument is a laser altimeter, which sends 10,000 pulses of light a second down to Earth's surface, and times how long it takes to return to the satellite – to within a billionth of a second. The instrument's pulse rate allows for a dense map of measurement over the ice sheet; its high precision allows scientists to determine how much an ice sheet changes over a year to within an inch.
The researchers took tracks of earlier ICESat measurements and overlaid the tracks of ICESat-2 measurements from 2019, and took data from the tens of millions of sites where the two data sets intersected. That gave them the elevation change, but to get to how much ice has been lost, the researchers developed a new model to convert volume change to mass change. The model calculated densities across the ice sheets to allow the total mass loss to be calculated.
This level of detail is essential for helping coastal residents and governments plan for sea level rise, which is expected to reach two to six feet by 2100, according to CNBC.
"Our goal is to be able to tell every coastal community what they can plan on [in] the coming decades," Bell told NPR. "To be able to do that, we both need to measure how the ice is changing but also understand better why it's changing."
Antarctica before and after its hottest day on record Feb. 6. NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey and GEOS-5 data from the Global Modeling and Assimilation Office at NASA GSFC.
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