[MUSIC PLAYING] FLORA LICHTMAN: Hey, I’m Flora Lichtman, and you’re listening to Science Friday. And now it’s time to play Name That Tune.

[GENTLE WATER SOUNDS]

No, it’s not a peaceful garden fountain. It’s not a babbling brook. You’re actually listening to tiny air bubbles burst out of glacier ice as it melts. Those sounds aren’t just the best white noise you’ve ever heard. They’re a possible source of data for researchers trying to better understand the rate of climate change and the impact of glacial meltwater.

Joining me now is Dr. Erin Pettit. She’s a professor of geophysics and glaciology at Oregon State University, and part of her work involves finding ways to safely monitor the behavior of some of the world’s biggest glaciers. Erin, welcome to Science Friday.

ERIN PETTIT: Hi, Flora. Thanks for inviting me.

FLORA LICHTMAN: Yeah. Oh, thanks for being here. So in that clip we played, it really does sound so much like trickling water, but it’s not. What are we hearing exactly?

ERIN PETTIT: Yeah, so when glaciers form, they form from snowfall high in the mountains. And that process ends up trapping air bubbles as the snow gets compressed into ice. And those little tiny bubbles travel through the glacier from way high up, whether it’s central Greenland, Antarctica, or just up in the mountains within the US. And they eventually make their way all the way down to the end of the glacier.

And there’s thousands, millions, kajillions of them in there. And as it melts out, each little air bubble is pressurized because it’s had this long journey, and it just goes “pop” into the water and oscillates a little bit. And so the sound will sound anywhere from the babbling brook, which is what we just heard. But if you’re a little farther away and the ice is melting a little bit faster, it can sound like a sizzling pan of food on the stove.

FLORA LICHTMAN: How do you get these sounds?

ERIN PETTIT: Sound travels amazingly well in water, and so oceanographers have been using sound for a long, long time to listen to what’s going on in the ocean. But until like 20 years ago, nobody had ever thought to really look closely at what’s going on at the terminus of a glacier. And part of that’s because it’s really hard to get there. It’s dangerous. These cliffs are calving. The ice is breaking off and forming icebergs.

There’s just a lot going on, and they can be quite dangerous to approach by a boat or a ship. And so we go up there and use sound. Because sound, you can be back a little ways. You don’t have to be quite as close to the glacier to really start to record some of the action happening. And I originally thought I was going to go to listen to calving events, but it turns out the bubbles and the sound of ice melting is as interesting or more than the calving events themselves.

FLORA LICHTMAN: Wait, why is it interesting to you?

ERIN PETTIT: It’s interesting to me because we’re losing ice everywhere in the world, and it’s really hard to keep track of how much we’re losing and where we’re losing it faster, where it’s melting faster, where it’s melting slower. But that’s really important to know so that we can start to, one, think about where that water goes. When ice turns into water, it contributes to the ocean.

And just being able to project into the future– what do we think is going to happen next with these glaciers? If they’re melting faster or slower underwater, that affects how they’re going to respond to changes in the future. We can put that into models. We can think about it. We can understand– like, just understanding the physics of what’s going on is huge for starting to put that into perspective of how all the ice is changing on the Earth.

FLORA LICHTMAN: Does a glacier that’s melting faster make a different sound than a glacier that’s melting slower?

ERIN PETTIT: For the most part, yes. We’re still struggling to put specific numbers on it because there’s a lot of slight differences, variability in that sound. But for the most part, if you have a whole bunch of bubbles that are uniformly distributed in your ice and then it melts, if it’s melting at a faster rate, there’ll be more bubbles coming out, which means the sound will be louder. And if there’s fewer, if it’s melting more slowly, the sound will be quieter.

And so in principle, it should be fairly simple to relate that sound to the melt of ice. The complications come in because there’s all sorts of icebergs. The shapes are all different sizes and shapes. And so it just– there’s other variables that come in that make it a little bit harder than we would like it to be, but it still gives us a lot of super interesting information that we can tease out from these sounds.

FLORA LICHTMAN: You mentioned wanting to record calving events, when big chunks break off of glaciers. Let’s hear what that sounds like.

[RUMBLING]

Is that the calving?

ERIN PETTIT: You can hear this low rumble that’s getting louder and louder and louder. This is a fairly large calving event, and it actually starts deep in the water. This rumble that’s starting is all of the fractures deep in the water column– very deep at the bottom of the glacial fjord.

The ice starts to break off, and then it slowly rises to the surface, and it’s tumbling through the water as it rises to the surface. And you can also hear some calving, or these fractures breaking off from above, and you hear the splashes at the top of the water. So we’re listening– that particular hydrophone, which is an underwater microphone, was planted on the bottom of the glacial fjord.

So it was sitting way down at the bottom of the fjord and listening to this event as it rose from the very bottom to the top. And it took like 45 seconds for that particular iceberg to make its way up from the bottom of the glacier to the top. And this is what we call a submarine calving event.

When you go as a tourist to glaciers, you always want to see the calving events that are from above water and that splash into the water. But these submarine ones are the ones that are super dangerous for boats because you can’t necessarily see them coming from up underneath your boat– then that’s a bit of a challenge, which is why most boat captains choose to stay their distance behind.

FLORA LICHTMAN: What can you learn about calving from listening to them? Could you predict calving events by listening to what happens before them, or what’s the goal with this part of the research?

ERIN PETTIT: Calving does start with the fracturing of the ice itself, which has a unique sound, and then this really low-frequency rumbling. And so in principle, you could get a little bit of an advance warning, like 30 seconds, maybe, but not really enough to do much with it.

The more interesting thing that we are exploring, our community is exploring, is, can we capture the size, the volume of ice in a particular calving event or the way that it moves through the water? Can we detect or document how much of an impact on the fjord circulation it’s having?

Like professional divers– they can go really smoothly through the water and not disturb it very much. Or if you think of the Olympics, if somebody messes up, they create a big splash. And so calving events are similar, in that sometimes they are sleek and they don’t disturb that environment very much. And other times, they will generate a lot of sloshing around. So that’s one of the things we’re interested in. And then the other one is just, how big are these calving events?

Because both of those things– how big the calving event is and how much of an impact on the fjord it is– come back to that same question of, how much ice are we losing? Because the iceberg itself is a loss of ice from the glacier, but then an iceberg that not only comes off, but then also sloshes the fjord and really energizes that water then contributes to additional melting of the ice. So some calving events have a bigger impact on that whole system and how much ice we lose than other calving events.

[MUSIC PLAYING]

FLORA LICHTMAN: Don’t go away because when we come back, using robots to explore these glaciers and whether there’s any hope at all in the field of glaciology. Stick around.

[MUSIC PLAYING]

I understand that you’ve been using robots to explore these glaciers as well. Will you tell me about that setup?

ERIN PETTIT: Yeah. So this is a system that we developed, again, because we wanted to be able to go measure what’s happening right at the glacier without putting ourselves in a dangerous situation. And so what we do is we are sitting back on a ship, a small research vessel, and then we put a Zodiac-type inflatable boat that is remote controlled, and we can drive that boat up to the glacier.

But then on this little boat, we have a little winch with a tethered ROV, so a remotely operated underwater vehicle. And then that remotely operated underwater vehicle has on it another remotely operated machine that actually can go drill itself into the glacier. And so we basically have four people that are deploying this. So we have one person driving the boat, one person driving this ROV on a tether, one person driving this little drilling mechanism that plants itself on the glacier, and then one person flying a drone overhead to be able to watch what’s happening. And so–

FLORA LICHTMAN: You can’t do it without a drone. You need a drone, too– yeah.

ERIN PETTIT: It can’t do it without a drone. And so we have this team of four. But it’s really amazing when this all comes together and we plant this platform on the glacier. And it screws itself in, and it will stay there for something like three to six hours. And we can mount– we put these hydrophones right there on that instrument. And this is like– it’s like three feet long. It’s not a very big platform. We will put measurement devices that can measure how fast the ice is melting, can measure the currents that are going on.

We have little video cameras that are watching what’s happening. And then we have our hydrophones that are listening. And so we can collect data for three hours and then get a sense of what’s going on with the glacier in that little area over those three-hour periods. We keep blowing our own minds by looking at these data again and again. We watch the same videos over and over again, and it’s really absolutely fascinating.

FLORA LICHTMAN: Wow. A remote-controlled boat deploying a remote-controlled ROV deploying a remote-controlled drill bot deploying a hydrophone and a video camera– how many times does it go right?

ERIN PETTIT: [CHUCKLES] We actually have had pretty darn good success. The four of us that are doing this installation– we like each other. So that means that if somebody’s messing up or something’s going wrong, we spend more time laughing and trying to get it right. But we also are really scared, because there’s hundreds of thousands of dollars worth of equipment that we could lose. So yeah, it actually– we practiced a lot on icebergs that are floating in a bit calmer water before going up to the glacier. But when we– we typically were successful like 50% of the time.

FLORA LICHTMAN: We know melting glaciers can disrupt ocean currents, which can have potentially huge effects on weather around the globe. Can you learn anything about that from listening to glaciers?

ERIN PETTIT: Yes, because we still– there’s so much we don’t about what happens right at the glacier, right where these glaciers tumble into the ocean. And it’s that tumbling that is why we don’t very much. People have been watching the glaciers from afar around Greenland, Alaska, Antarctica, but it’s been really tricky to get up close to really see what’s happening. And because of that, we really have been missing some of the really small-scale physical processes that are going on, like how ice melts.

We really actually don’t very well how the glaciers melt into the ocean or what triggers a calving event or any of these questions that seem like we would have figured them out by now. And they do play a role in how we take those small-scale processes and scale them up to try to implement them in, say, a larger-scale model for what the future of Greenland is. What happens at a millimeter, centimeter, a meter can help us understand what happens across the entire Greenland ice sheet.

FLORA LICHTMAN: Is there anything melancholy to you about these sounds? Do you feel like you’re capturing sound that may not exist on our planet in the future?

ERIN PETTIT: That’s a good question. There certainly is. Ice melting is part of the natural process. Snow falls up high and then it melts or breaks off down low. And so even in a climate in which we were growing glaciers, we would still have sounds of ice melting. But it is quite a bit more now than normal, and we are listening to this ice loss that is not being recovered by snowfall upstream.

And yes, there is some melancholy to it. There’s a– it makes me just think and reflect on the world around me. And hopefully our whole society can think about and reflect on the world around us. We get asked this often as climate scientists, like, are we depressed? Is it really sad to be studying this stuff all the time?

And– yes and no. I do feel like we need to be– we need to be paying attention to what goes on around us and listening, whether it’s just listening and looking around your own environment at home or listening to glaciers in the polar regions. And so, for me, yes, there’s a sadness for this loss, but there’s also just an absolute fascinating, beautiful aspect to realizing that we still don’t understand a lot of what goes on around us. There’s just a richness that is fascinating.

FLORA LICHTMAN: Do you have a favorite sound that we can play as we go out of this segment?

ERIN PETTIT: A favorite sound– that’s like asking me if I have a favorite glacier. They’re all unique and beautiful in their own way.

FLORA LICHTMAN: You probably do. I know we like to say we don’t, but– so which one should we listen to?

ERIN PETTIT: I think listening to one from underneath the Thwaites Ice Shelf in Antarctica. So we were camped on top, and we drilled through 300 meters, a thousand feet of ice, into the water below this floating part of the glacier. And this is the Thwaites Glacier, which is also known as the Doomsday Glacier, which is not my favorite label for it. But it’s eerie, like you’re in this huge cavity of– yeah. And there are seals that you can hear in the distance, and then there’s cracks that are not calving events. They are actual fracturing of the ice.

[SIZZLING]

[WHISTLING]

And there’s not much of that sizzling bubble sound because the ice down there– the bubbles are so pressurized that they can’t really pop out in the same way, and they dissolve into the water too quickly. So it’s much quieter, which gives it a very, very different perspective than some of the Alaskan glaciers.

FLORA LICHTMAN: Hmm. Erin, thanks for letting us listen in on this remote part of the world. Appreciate it.

ERIN PETTIT: Yeah, thanks for inviting me.

FLORA LICHTMAN: Dr. Erin Pettit is a glaciologist at Oregon State University. This podcast was produced by Charles Bergquist. If you have questions you think SciFri should tackle, give us a call– 877-4-SCIFRI. Our listener line is always open, but, no, we will not do your homework for you. Thanks for listening. I’m Flora Lichtman.

[MUSIC PLAYING]

Copyright © 2025 Science Friday Initiative. All rights reserved. Science Friday transcripts are produced on a tight deadline by 3Play Media. Fidelity to the original aired/published audio or video file might vary, and text might be updated or amended in the future. For the authoritative record of Science Friday’s programming, please visit the original aired/published recording. For terms of use and more information, visit our policies pages at http://www.sciencefriday.com/about/policies/