The era of the oldest ice on Earth mystery: NPR

Preparing for drilling the oldest ice cores on Earth. The photo captures the interior of a Blue Ice Drill (BID) tent with diggers Tanner Kuhl (left) and Elizabeth Morton (right). Graduate students Austin Carter, Jacob Morgan, and postdoctoral fellow Dr. Sarah Shackleton in the background. Alan Hills, Antarctica, 2019.

John Higgins


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John Higgins

Preparing for drilling the oldest ice cores on Earth. The photo captures the interior of a Blue Ice Drill (BID) tent with diggers Tanner Kuhl (left) and Elizabeth Morton (right). Graduate students Austin Carter, Jacob Morgan, and postdoctoral fellow Dr. Sarah Shackleton in the background. Alan Hills, Antarctica, 2019.

John Higgins

Perhaps the oldest ice on Earth is hidden somewhere in Antarctica, because this frozen continent contains ice hundreds of thousands and even millions of years old. Scientists hope to find it.

But even scientists searching for ancient ice aren’t sure how long the oldest ice might have been trapped John HigginsGeochemist at Princeton University.

“Would I be surprised at this point if we had 5 million years old ice?” Higgins asks. “I mean, I’d be surprised, but that’s not far-fetched.”

One group already has it claimed To find an eight-million-year-old ice in a buried glacier, and to determine the age by dating volcanic ash on the ice, some experts have their doubts.

“My position is that I accept that it is old ice. I don’t know if it is exactly 8 million, but I accept that it is old ice,” he says. Eric Wolf, Climate Scientist at the University of Cambridge in the United Kingdom.

The problem, he says, is that the sample ice in particular is a “real mess” and is pointless to scientists who are only looking for ancient ice because of something special trapped inside: small samples of old air from the time the ice formed.

“When you pull the ice, it’s basically pretty clear but full of little bubbles,” explains Higgins. He considers these bubbles to be the second best thing to having a time machine that allows scientists to go back and collect past air directly.

Higgins and some colleagues recently drilled a sample of ice in Allan Hills The Antarctic region, which, by analyzing trace amounts of argon, was later found to be 2.6 million years old. In his opinion, this is “the oldest thing that I think we have high confidence in an ice age and an age of air trapped in ice.”

A slightly smaller 2-million-year-old specimen found nearby was pure enough to use its bubbles Measure Important greenhouse gases such as carbon dioxide and methane, providing a snapshot of the atmosphere at the time a challenge Scholars’ previous assumptions.

Base camp on blue ice. Field teams of 5-8 scientists and ice core riggers spent up to 8 weeks living on ice from November to January in 2015-2016 and 2019-2020. The tents of the smaller pyramid (Scott) are the sleeping and toilet areas while the large tent in the middle is the cooking tent. Allan Hills, Antarctica, December 2015.

John Higgins

Understanding how carbon dioxide levels have changed throughout Earth’s history can help climate researchers understand how human activities will warm the planet in the future. “One of the biggest questions about recent warming and anthropogenic climate change is how much warming should we expect with the amount of carbon dioxide in the atmosphere,” he says Sarah Shackleton, Another Princeton researcher.

Sometimes you thaw very old ice in the lab and see old gases pouring through the liquid, which is what she calls a “wizard”.

“The one thing that really amazes me, every time, is the amount of gas in the ice,” says Shackleton, adding that atmospheric gases make up about ten percent of the volume of glacier.

All of this is why researchers have been keen to find ice from key time points in Earth’s climate history, such as periods of unexplained changes in the cycles of warming and cooling.

An ice sheet covered Antarctica for at least 30 million years, but very old ice is still hard to find.

Snowfall is constantly adding new layers of ice to the top of the Antarctic Ice Sheet. However, the oldest layers below could melt due to geothermal heat coming from the earth.

“The rocks release heat slowly over time, so they have the ability to melt the ice at the bottom,” he explains John Judge, Geoscientist at the University of Minnesota.

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However, bits of ancient ice – such as that 2.6 million-year-old specimen – can sometimes be preserved at the edges of the ice sheet.

“The oldest chunks of ice that we have been able to find come from places where the snow poured over a mountain range and were exposed to the surface,” Judge says.

However, in those places the ice can be messy and mixed, or present in secluded pockets. They are not gentle layers laid down sequentially throughout the Earth’s continuous history.

To get precisely this kind of layered ice sample, scientists need to drill straight down through the thick Antarctic ice sheet. To date, the oldest ice collected in this way is traced back 800,000 Years.

Now, many groups from all over the world want to hunt for ice that is older, over 1.5 million years old.

“Whether we will be able to find it at the bottom of the ice sheet, where we can recover a relatively simple record, I think that’s the $ 64,000 question,” says Goodge.

He notes that drilling through nearly two miles of solid ice is difficult and will take many years, making it important to target the most promising spot.

European Project Already selected Its location, an arid place called “Little Dome C” where the temperature is always below -13 degrees Fahrenheit.

“We’ve already set up the pit tent and part of the campsite is on site,” says Wolf. “And so next November, a team has to go to set up the drilling and start digging.”

Barbara Steny From Ca’Foscari University thinks there is a “good possibility” to find ice 1.5 million years old or more at this location, and points out Results An ice-penetrating radar scan supports this idea. “Physical evidence tells us that this ice might even exist,” she says.

Meanwhile, the researchers were from China drilling Deep in ancient ice at a place called Dome A. “It might or might not work” Jeffrey Severinghouse From the Scripps Institute of Oceanography, University of California, San Diego, explaining that the site was chosen because it is close to a research station. “It wasn’t really chosen with the goal of having the kind of best ancient ice site possible.”

He’s been working with Goodge to develop a new kind of speed Exercises It can penetrate the ice cap quickly, in days instead of years, so researchers can assess different locations before committing to more detailed and costly drilling.

“My feeling was that the actual presence of very ancient ice at the bottom of the glacier would be very difficult to predict in advance using traditional methods like radar and things like that,” says Seafringhouse.

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With their drill, it would be possible to make multiple holes and run tests on ice at the bottom, he says, “until you know for sure that ancient ice is there.”

Drilling is in progress. Graduate student Gina Epifanio keeps the drill barrel straight while drilling operator Tanner Cole lowers it into the hole. The 2019-2020 expedition focused on recovering large-scale samples from more than two million years of ice discovered in 2015-2016. Alan Hills, Antarctica, 2019.

John Higgins


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John Higgins

Drilling is in progress. Graduate student Gina Epifanio keeps the drill barrel straight while drilling operator Tanner Cole lowers it into the hole. The 2019-2020 expedition focused on recovering large-scale samples from more than two million years of ice discovered in 2015-2016. Alan Hills, Antarctica, 2019.

John Higgins

The coronavirus pandemic has delayed his team’s work – in fact, the virus has forced researchers to cancel nearly the entire field season in Antarctica. But in the fall of 2021, old ice hunters will return.

If any of these efforts ultimately allowed scientists to obtain a continuous sequence of ice sheets dating back 1.5 million years or more, they would be able to understand the atmospheric changes that occurred during the important climate transition..

About a million years ago, there was a major shift in the cycle of ice ages on planet Earth. They used to come every 40,000 years or so, but for some reason that pattern ended – and changed to every 100,000 years instead.

“For us climate action, that’s a really big problem,” says Wolf. “It’s a really big question about why this change is, because it’s fundamental to how our climate system works. In a way, you could say we don’t really understand today’s climate if we don’t understand why we’re living in a 100,000-year and not a 40,000-year-old world.”

Glaciers are clearly coming and going because of influences that are not well understood, agrees Severinghouse, who thinks “we have to know about these in order to predict our future.”

While some of these mysteries can be solved by digging continuous ice cores dating back 1.5 million years or finding isolated bits of ice up to 5 million years old, he says, “There is no reason why we should not be lucky and find something older.” “

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