Science Friday - What The Sounds Of Melting Glaciers Can Tell Us

Episode Date: December 11, 2025

As the planet warms, the world’s glaciers are melting faster than snow can replenish the ice. That has implications for sea level rise, ocean currents, and global weather patterns. But collecting data at the edge of a melting glacier can be risky.Glaciologist Erin Pettit and her colleagues are listening to the sounds melting glaciers make—from the sizzling of trapped air bubbles bursting, to the deep rumbles of underwater calving of icebergs. She joins Host Flora Lichtman to share some glacial sounds, and describe the multi-stage robot tools she uses to monitor melting ice.Guest: Dr. Erin Pettit is a professor of geophysics and glaciology at Oregon State University.Transcripts for each episode are available within 1-3 days at sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Hey, I'm Flor Lichten, and you're listening to Science Friday. And now it's time to play, Name That Tune. 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 resources. trying to better understand the rate of climate change and the impact of glacial meltwater.

Joining me now is Dr. Aaron 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. Hi, Flora. Thanks for inviting me. Yeah. Oh, thanks for being here. Okay. So in that clip we played, it really does sound so much like trickling. water. But it's not. What are we hearing exactly? 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 U.S. and they eventually make their way all the way down to the end of the glacier. And there's thousands, millions, cajillions 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, sizzling pan of food on the stove. How do you get these sounds? Sound travels amazingly well in water. 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. Like 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, right? 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. Wait, why is it interesting to you? 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, if they're melting faster, 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. Does a glacier that's melting faster make a difference sound than a glacier that's melting slower? 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 like all sorts of icebergs, there's the shapes are all different sizes. and shapes. And so 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. You mentioned wanting to record calving events

when big chunks break off of glaciers. Let's hear what that sounds like. Is that the calving? 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 like 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... some calving, 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. Come up underneath your boat,

then that's a bit of a challenge, which is why most boat captains choose to stay. distance behind. What can you learn about calving from listening to them? Like, could you predict calving events by listening to what happens before them, or what's the goal with this part of the research? Calving does start with the fracturing of the ice itself, which has a kind of a unique sound, and then these, 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 fuel? circulation it's having like professional divers, they can go really smoothly through the water and not disturb it very much. Or, you know, if you think of the Olympics, if somebody messes up, they create a big splash, right? And so having events are similar and 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 slashes 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 capping events. 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. I understand that you've been using robots to explore these glaciers as well.

Will you tell me about that setup? Yeah. So this is a system that we developed because of, 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 like 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 this, we basically have four people that are deploying this. So we have one person driving the boat, one person driving this ROViana 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 this- Can't do it without a drone.

You need a drone, too. 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 can, it screws itself in and it will stay there for something like, you know, three to six hours. And it's, and we can mount. We put these hydrofoam. right there on that instrument. And this is like a, you know, 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. It's, we keep kind of 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. Wow. I mean, you know, a remote-controlled boat deploying a remote-controlled RV, deploying a remote-controlled drill bot, deploying a hydrophone and a video camera, how many times does it go right? We actually have had pretty darn good success. of us that are doing this installation, we like each other. So that means that like if somebody's messing up or something's going wrong, we spend more time kind of laughing and trying to, 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. You know, we know melting glaciers can disrupt ocean currents, which can have, you know, potentially huge effects on weather around the globe. Can you learn anything about that from listening to glaciers? Yes, because we still, there's so much we don't know 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 know very much. You know, 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. Like, we really actually don't know 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 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. 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?

That's a good question. there certainly is. I mean, ice melting is part of the natural process, like 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 up upstream. And yes, there is some melancholy to it. There's a, it makes me just kind of 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. Like, 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 a 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. Do you have a favorite sound that we can play as we go out of this segment? A favorite sound. That's like asking me if I have a favorite glacier. They're all unique and beautiful in their own way. You know, you probably do. I know we like to say we don't, but so which

one should we listen to? I think listening to one from underneath the Thwait's 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 kind of eerie, like you're in this huge cavity of, yeah, and there's 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. And there's not much of that. sizzling bubble sound because the ice down there, the bubbles have, are so pressurized, but 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. Erin, thanks for letting us listen in on this remote part of the world. Appreciate it. Yeah, thanks for inviting me.

Dr. Aaron Pettettit is a glaciologist at Oregon State University. This podcast was produced by Charles Berkwist. If you have questions you think SciFRI should tackle, give us a call. 877 for SciFRI. Our listener line is always open, but no, we will not do your homework for you. Thanks for listening. I'm Flora Lichtman.