Searching For The World's Oldest Ice : Short Wave Scientists think the world's oldest ice is hiding somewhere in Antarctica. NPR science correspondent Nell Greenfieldboyce tells us how researchers plan to find it — and why.

For more, you can also read Nell's story, "Scientists Have Found Some Truly Ancient Ice, But Now They Want Ice That's Even Older."

Email the show at shortwave@npr.org.
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The Hunt For The World's Oldest Ice

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The Hunt For The World's Oldest Ice

The Hunt For The World's Oldest Ice

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EMILY KWONG, HOST:

Hey, everybody. Emily Kwong here. We are watching closely the events that are unfolding in Washington, D.C. For the latest news, tune to your local NPR station or go to npr.org. Thanks for listening. And here's the show.

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KWONG: You're listening to SHORT WAVE from NPR.

Hey, everybody. Emily Kwong here with NPR science correspondent Nell Greenfieldboyce. Hey, Nell.

NELL GREENFIELDBOYCE, BYLINE: Hello, Emily.

KWONG: So 2020 is in our rearview mirror. We are embracing a new year. But at least in this hemisphere, it is still winter.

GREENFIELDBOYCE: We're getting more daylight, though. I mean, the days are getting longer.

KWONG: Yeah, that's true. But it's still cold, which frequently means we're dealing with ice. And I spent years in Alaska. Ice as an old friend and foe of mine. And this time of year, I'm just saying, it brings a lot of ice.

GREENFIELDBOYCE: It depends on where you are but yeah. Yeah. I mean, I love ice. I love it. I think it's beautiful. And, you know, obviously it's a nightmare, but I do like it.

KWONG: Yeah. Many people are happy to see it disappear when spring comes. And that is kind of how ice is for most of us - it comes, it goes. But I know you recently were looking into ice that doesn't go away, ice that sticks around for a long, long time.

GREENFIELDBOYCE: Indeed. I wanted to know what the oldest ice on Earth is.

KWONG: The oldest ice on Earth. Is there any chance it's in Alaska?

GREENFIELDBOYCE: Well, it's most likely down in Antarctica, I'm sorry to tell you.

KWONG: That's all right. Most likely - so scientists don't know?

GREENFIELDBOYCE: Well, Antarctica is the most likely spot because it's been covered by an ice sheet for at least 30 million years. Now, that doesn't mean the ice down there now is that old. But we do know this continent has ice that's truly ancient. I mean, scientists have already found ice in Antarctica that's millions of years old. And because scientists are never satisfied...

KWONG: Yeah, never satisfied.

GREENFIELDBOYCE: Never, never satisfied. They are hunting for ice that is even older.

(SOUNDBITE OF MUSIC)

KWONG: All right. Today on the show, the hunt for the planet's oldest ice. We'll look at why scientists care about ancient ice, how they are searching and what they might find. I'm Emily Kwong, and you're listening to SHORT WAVE from NPR.

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KWONG: All right. Nell, other than the fact that it is cool, why do scientists want to find ancient ice?

GREENFIELDBOYCE: They're really after something that's inside the ice, basically air bubbles. And, you know, a lot of times in an ice sample, you can actually see them. They're just these little clear spherical bubbles inside clear ice. It's beautiful. And I talked to this geochemist named John Higgins from Princeton University. He told me when ice forms, atmospheric gases get trapped inside these bubbles. And they're preserved there for hundreds of thousands, even millions of years.

JOHN HIGGINS: You know, you can't really do better other than getting a time machine and going back in time and taking an air sample, then using these ice cores, which, you know, physically just trap samples of ancient air.

KWONG: So if these air bubbles are kind of like time capsules, what is it from the past that they're trying to measure?

GREENFIELDBOYCE: So you can imagine that, you know, looking at something like greenhouse gases, carbon dioxide would be super interesting. Like, you could see how levels have changed over the planet's history. And that could help you understand how those gases relate to climate and how the future climate might change, you know, as those gases change from human activity, that kind of thing.

KWONG: And how do they get these gases out of the ice?

GREENFIELDBOYCE: What I love is that it's really simple. To get the gases out, all you have to do is melt the ice. And Higgins showed me this one video made by the manager of the research camp where he worked in Antarctica with his colleagues. And she was making drinking water by just melting leftover scraps of ice from where they were drilling. So she was just like, you know, casually melting 200,000-year-old bits of ice in this metal pot.

(SOUNDBITE OF WATER DRIPPING)

GREENFIELDBOYCE: So, you know, you can hear the bubbles, the gases coming out. And, you know, with that water, they were just making coffee or whatever. But obviously, if you want to actually do science with the gases, you have to melt the ice in a lab. So you'd melt it in like a glass vial that's sealed up so that you can collect all the gases that are bubbling out. I talked to Sarah Shackleton, who works at Princeton with Higgins. And she says she just loves melting this stuff in the lab and watching that happen.

SARAH SHACKLETON: That is something that I don't know if I'll ever get sick of watching. It's actually like pretty mesmerizing. And one thing that's really surprising every time to me is just how much gas is actually in the ice.

GREENFIELDBOYCE: She says, you know, it's a lot.

KWONG: And, Nell, what is the oldest ice that these folks have collected and melted like that?

GREENFIELDBOYCE: Researchers at Princeton led a team that found one ice sample that was about 2.6 million years old.

KWONG: Whoa.

GREENFIELDBOYCE: And, you know, they managed to get really good carbon dioxide and methane measurements from another sample. That one was 2 million years old.

KWONG: And is that the oldest ice ever found, about 2.6 million years old?

GREENFIELDBOYCE: There is another research group that said they found 8-million-year-old ice, like, buried under some dirt and volcanic ash and stuff. But not everybody buys that one. And the sample was so messy, the gases in it couldn't really be analyzed in the way that people want. So, you know, that 2-million-year-old ice sample is like the oldest, undisputed one that gases have been taken from and measured.

And, you know, you might say, well, how do they know the ice is that old? And it's because they're able to analyze the trace noble gas argon. Let's not get into all the details here. But basically, they know how argon has been slowly changing the atmosphere for like billions of years.

KWONG: So they're kind of using the argon as a reference point for calculating the age of the ice?

GREENFIELDBOYCE: Yes.

KWONG: Those noble gases - so useful. And 2.6 million years old seems pretty old. I mean, what more could an ice scientist want?

GREENFIELDBOYCE: So I asked Higgins, like, when you go looking for old ice, what's the oldest do you think you could get?

KWONG: Yeah.

HIGGINS: You know, would I be surprised at this point if we had 5-million-year-old ice? I mean, I'd be surprised, but not - it's not unfathomable, I think.

KWONG: Where do you even find old ice? Because when I look at photos of Antarctica, Nell. it is covered with ice. And it all looks pretty much the same. So how do the scientists decide where to go?

GREENFIELDBOYCE: So this was interesting to me. Here's the thing. Every year, it snows. And that snowfall creates a new layer on top of the ice sheet. So you can imagine that as you go deeper and deeper down into the ice sheet, the ice gets older and older, right? So, like, it's sort of like rings on a tree, right? You know, the youngest ice layers are on the top and then the oldest are down at the bottom.

HIGGINS: And it sounds like if you want old ice, you should go to the bottom.

GREENFIELDBOYCE: Yeah, except here's the thing. The ice at the bottom is right next to the bedrock, right? And I talked to John Goodge. He's a geologist at the University of Minnesota. And he told me that coming up from those rocks is actually a small amount of heat, geothermal heat.

JOHN GOODGE: So the rocks are giving off heat slowly over time. And so that has the potential to melt ice at the bottom.

KWONG: So if the ice at the bottom is melting anyway, maybe you don't want to spend your time looking there.

GREENFIELDBOYCE: Yeah. So the oldest bits of ice that have been found so far, like that 2.6-million-year-old ice, have been found in weird spots like the edges of the ice sheet, where the ice somehow gets protected from melting. Maybe it flowed up and was exposed to the cold surface and preserved. Higgins has been looking for ancient ice in those kinds of oddball places. And, you know, the ice there can be kind of all jumbled up. It's not in like nice layers that have been laid down sequentially over a long, continuous stretch of Earth's history.

KWONG: And ideally, I suppose, to understand the history of how Earth's atmosphere has changed over time, you'd want an ice sample with those nice layers, right? Because that way you could get bubbles of gas from the whole continuous stretch of history and not just one moment that scientists happen to find, like it'd be like trying to understand a book by reading only one page.

GREENFIELDBOYCE: Well, I think both things could be valuable, right? I mean, you could find random snapshots from super-old time periods, you know, in these weird places. And then you could also use those along with younger ice samples, you know, ones that give you a more continuous record. I mean, you're right. Scientists do want ice samples with those nice sequential layers. I mean, they want that kind of thing a lot. You know, it's really important for reconstructing the history of the Earth's atmosphere and how it relates to climate.

KWONG: So when it comes to an ice sample like that, one with sequential layers going back over a continuous stretch of time, what is the oldest sample that scientists have been able to get?

GREENFIELDBOYCE: The oldest sample like that is a long cylinder of ice with layers that go back 800,000 years.

KWONG: Wow.

GREENFIELDBOYCE: That's a long time. But researchers now want to drill down through the ice sheet to get a cylinder with layers that go back twice as far, to like a million-and-a-half years ago. And there are groups working on that right now.

KWONG: Yeah, a million-and-a-half years. How far down are they going to have to drill?

GREENFIELDBOYCE: It's like a couple of miles down.

KWONG: This is not the same thing at all, but I have gone ice fishing. And drilling a couple of miles through solid ice? That does not sound easy.

GREENFIELDBOYCE: It's a big commitment. I mean, as you can imagine, it's - you know, and they're down in Antarctica, you know, where the weather isn't always, like, super cooperative. I mean, it'll take years. There's one group from China that's already drilling at one spot in Antarctica. And another group from Europe has picked a promising spot. You know, they're going to start drilling in November. There's another group of people like Goodge who've developed this kind of rapid drill that lets them, you know, test different areas to see, like, what might be the best place. So, you know, the hope is that there could be eventually, like, more than one sample. And, you know, they're thinking they can get ice that's super old.

KWONG: And if one of these groups is successful, is there something we'll ultimately know that we don't now know? Like, what is the - I guess what is the motivation for getting layers of ice that go back that far?

GREENFIELDBOYCE: What really everyone wants is ice samples that cover a key time period about a million years ago. I talked to Eric Wolff. He's a climatologist at the University of Cambridge. He told me that a million years ago is when there was this dramatic shift in the planet's cycle of ice ages. So those had been coming every 40,000 years or so, but for some reason that changed to every 100,000 years instead.

ERIC WOLFF: It's a really big question as to why that changed 'cause 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 live in a hundred-thousand-year world rather than a 40,000-year world.

GREENFIELDBOYCE: And basically, if scientists want to make predictions about how our climate will change in the future, you know, respond to increased carbon dioxide levels from all our human activity, they really need to understand this kind of stuff.

KWONG: Last question. Has this hunt been affected by this pandemic?

GREENFIELDBOYCE: Yeah, it seems like everything's been affected by the pandemic.

KWONG: True. True.

GREENFIELDBOYCE: And yes, this research was put on hold because of the coronavirus. The whole Antarctic research season was basically put on hold. But they'll be back down in Antarctica for the next research season, which starts towards the end of this year.

KWONG: Well, Nell, please keep us posted on what they find. And enjoy the winter and whatever ice you get.

GREENFIELDBOYCE: Watch out for the black ice, Emily.

KWONG: I will. I will.

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KWONG: This episode was produced by Rebecca Ramirez, edited by Gisele Grayson and fact-checked by Ariela Zebede. I'm Emily Kwong. Thanks for listening to SHORT WAVE from NPR.

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