The dangers of warming winter lakes

Over half a billion people live by lakes that freeze over in the winter. But as the climate warms, those lakes are losing whole days of ice cover. Winters are also getting weirder, with more intense temperature swings that lead to multiple freezes and thaws. Those fluctuations make the ice less safe, and more likely for people to fall through as they walk. So, today, producer Berly McCoy https://www.npr.org/people/985775371/berly-mccoy gets into how these changes are altering culture, community and safety on the ice – plus, how firefighters train for rescues. This is the first in a two-part series on how lake ice is changing. Check out Monday’s episode for part two! Check out photos https://npr.org/sections/the-picture-show/2026/02/27/g-s1-111346/madison-wisconsin-frozen-assets-festival from Berly’s reporting trip to Madison, Wisconsin. Interested in more winter science? Email us your question at [email protected] mailto:[email protected]. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:00Speaker 00

  This message comes from University of Buffalo, where scientists are working to protect the Great Lakes and freshwater supplies around the world from harmful contamination. Learn more about their research at buffalo.edu/npr.

• 0:15Speaker 00

  You're listening to Short Wave from NPR.

• 0:20Emily Kwong?

  Hey, Shortwavers. Emily Kwong here. Quick reminder, Short Wave comes out four days a week, Monday through Wednesday and Friday. So to make sure you never miss an episode, look for the follow button on your podcast app and give it a little boop. Thank you kindly. All right, now, it's my great pleasure to welcome Short Wave producer Burleigh McCoy. Hey, Burleigh.

• 0:39Speaker 02

  Hey, Emily. So as you know, winter is my dam. I ice fish all winter on a frozen lake in northwest Montana, where I live.

• 0:48Emily Kwong?

  Yes, you are our resident Short Wave ice queen.

• 0:50Speaker 02

  Thank you. And I'm not the only one who takes ice seriously. Almost every year since 2011, a huge lake in Madison, Wisconsin, has frozen over enough to support an entire festival. It's called Frozen Assets, and that's where I headed to report this story.

• 1:05Emily Kwong?

  Ooh, this sounds fun. What happens at Frozen Assets?

• 1:10Speaker 02

  So on and near the ice of Lake Mendota, there is ice hockey, curling, ice skating. People are flying these giant, colorful kites on the ice. A skydiver is landing on the ice right now.

• 1:25Emily Kwong?

  That's incredible.

• 1:26Speaker 02

  And they did this warm up for a 5K where more than 1,000 people jump up and down on the ice to make it shake.

• 1:34Emily Kwong?

  What? Why would you do that?

• 1:36Speaker 02

  I don't know. I did not like it.

• 1:38Speaker 03

  This lake is over 14 inches, so it's safe. But can it shake?

• 1:44Speaker 02

  So this is James Thai, the executive director and founder of Clean Lakes Alliance, which puts on the festival. But Emily, this lake, which freezes every year, this year with ice thick enough that it could have held an entire fleet of trucks, might one day not freeze at all. And thousands of others may stop too, like, soon.

• 2:04Emily Kwong?

  I could foresee in my lifetime, certainly in winter, when Mendota doesn't freeze.

• 2:09Speaker 02

  Today on the show, how changing lake ice is altering culture, community, and safety on the ice. Plus, I go out with Madison's Lake Rescue Team to see how they train for emergencies when someone falls through.

• 2:22Speaker 00

  You're listening to Short Wave, the science podcast from NPR.

• 2:29Speaker 00

  Stay tuned for the following announcements and messages from our sponsors. This message comes from University of Buffalo, where scientists are working to protect the Great Lakes and freshwater supplies around the world from harmful contamination. Learn more about their research at buffalo.edu NPR. This message comes from Mint Mobile. While others have been hiking your bill, Mint Mobile has kept their wireless plans starting at $15 a month. Switch to Mint Mobile and get three months of premium wireless service for $15 a month. Go to mintmobile.com/switch. Upfront payment of $45 for three-month plan required. $15 per month equivalent. New customer offer first three months only, then full-price plan options available. Taxes and fees extra.

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• 3:44Emily Kwong?

  All right, Burley, so we are talking about lake ice, which, remind me, when is it safe to walk on lake ice?

• 3:51Speaker 02

  Yeah, so I double-checked this with Hilary Dugan at the festival. She's a scientist who studies inland lakes, and she says it's safe for a person to walk on ice when there is four inches of black ice.

• 4:01Speaker 05

  Black ice is really strong, and it's what freezes in the lake water itself. So it's what's freezing downward.

• 4:09Speaker 02

  So black ice, which is called that because it's clear and appears black, is strongest, but it's not the only type of ice.

• 4:17Speaker 05

  White ice is what's forming when you freeze snow or slush. And that white ice has a lot more air in it, just weaker in general.

• 4:25Speaker 02

  Because of all the air, white ice scatters more light, isn't clear, and it looks white. It's less strong, and so it's less safe. And unlike black ice, it's tricky to say how much white ice is safe to walk on because the amount of air in it can be variable, and it's often mixed with black ice.

• 4:41Emily Kwong?

  Hmm, OK. So you went to this festival on a frozen lake with clearly enough black ice for you to stand on.

• 4:48Speaker 02

  Yes.

• 4:49Emily Kwong?

  And it sounds true to the spirit of northern communities. I mean, celebrating winter and making it a part of the culture there.

• 4:56Speaker 02

  Absolutely. That's very true in Madison. In many places downtown, people can always see one of the two lakes surrounding the city. It's just part of everyday life there. And a lot of people take advantage of that. In one of the lakes, there's this bay where in the winter, dozens, if not hundreds of people are ice fishing every day. I mean, this is a place that embraces winter. When I was at the Frozen Assets Festival, we walked by people eating snow cones. It was 10 degrees outside.

• 5:22Emily Kwong?

  I spent some years in Maine and in Alaska, and it reminds me of lacing up my skates on the weekend just to go out on the lake and have fun. Though, it also reminds me of how nervous I was every time to step on it. I could not imagine going out to a whole festival on a lake. That's a lot of weight on that body of water.

• 5:39Speaker 02

  Though, at Lake Mendota, it's not every year anymore.

• 5:43Emily Kwong?

  Oh.

• 5:44Speaker 02

  Hillary told me that Lake Mendota does freeze over every year. There's even a contest where people guess what day that'll happen. But two years ago, the ice didn't form thick enough in time for the festival.

• 5:55Speaker 05

  So the festival on the ice was canceled and it was sort of moved to the shore, which was really unfortunate. It was still fun, you know, we still had a lot of the same things, but you know, it takes away of the spirit of what this festival's about.

• 6:06Emily Kwong?

  But at the same time, better for people to be on solid ground, you know?

• 6:10Speaker 02

  Yeah, and that made me wonder about safety on lake ice and how it might be changing. So I went to another expert. I'll let him introduce himself.

• 6:18Speaker 06

  Justin Toos. I'm a firefighter down at Station 1 Madison, Wisconsin Fire Department.

• 6:23Speaker 02

  Justin is part of the Lake Rescue Team, a group of firefighters who, among other things, are professionally trained to dive and rescue people who have fallen through the ice. I joined them on one of their training exercises.

• 6:34Emily Kwong?

  Nice.

• 6:35Speaker 02

  So we went to Lake Monona, which is also right in town, to a spot where a river flows into the lake, which basically means there's always open water in that area.

• 6:43Emily Kwong?

  Ooh, sounds like the perfect place for practicing rescues if you're the Madison, Wisconsin Fire Department.

• 6:49Speaker 02

  I think that's exactly the thought. So I put on this giant yellow immersion suit. On it goes.

• 6:56Speaker 06

  Got it?

• 6:57Speaker 02

  Yeah. They call it a Gumby suit because you basically walk like the green claymation character Gumby if you try to move.

• 7:04Speaker 06

  Kind of one size fits all, so they might be a little...

• 7:08Speaker 07

  One size fits all usually means men's size.

• 7:11Speaker 02

  So I followed a couple of firefighters also wearing these suits onto the ice, including Justin. We walked parallel to the river at first and started moving toward it. We stepped over this huge ice crack where you could see the water. And they told me it's features like these. They can form from warmer water flowing into a lake or from like natural ice expansions and contractions. These are the places weaker ice can exist and are often where people will fall in.

• 7:38Emily Kwong?

  Mmm.

• 7:38Speaker 02

  So we cleared the crack, walked right to the edge of where the ice stops and the lake water starts. Justin got in first.

• 7:45Speaker 06

  Yeah, whenever you're ready to try it, we can throw you in.

• 7:48Emily Kwong?

  I'm ready.

• 7:48Speaker 06

  Alright. Hey Lou, Burley's gonna go in.

• 7:51Speaker 02

  They didn't throw me in. I kinda got down on the ice then went in backwards off the edge.

• 7:55Speaker 06

  Alright, so it's actually only like four feet here, so you can't touch. You'll feel a little pressure on your legs.

• 8:01Emily Kwong?

  Alright, oh, this is nice.

• 8:02Speaker 06

  Yeah. So if you wanna lean back, I can hold on to you, you can kinda feel how it is. So it's super buoyant.

• 8:08Speaker 07

  Yeah.

• 8:09Speaker 06

  Yeah. It'll keep you warm. Actually, like the longer you're in it, the warmer you get.

• 8:15Speaker 02

  And I just floated there while holding on to the ice for a few minutes.

• 8:19Emily Kwong?

  Was it cold?

• 8:20Speaker 02

  No, I was in this suit that made it kind of comfortable.

• 8:24Emily Kwong?

  Oh.

• 8:25Speaker 02

  And I had the lake rescue team around, so it wasn't scary or anything. It was pretty much the safest situation I could ever be in going into a frozen lake.

• 8:33Speaker 08

  Ready to get rescued?

• 8:35Emily Kwong?

  I'm ready to get rescued.

• 8:36Speaker 08

  Alright.

• 8:36Speaker 02

  So another team member brought over this bright yellow rescue sled and attached my arms into a thick loop. We're gonna pull her out. Then he flagged the shore team to start pulling on this ice anchored rope that was attached to the sled.

• 8:52Emily Kwong?

  Get her out, gentlemen.

• 8:55Speaker 02

  It was all pretty quick.

• 8:56Emily Kwong?

  Cool to hear how they practice. How often are they doing it in reality? Like, how often are they rescuing people?

• 9:03Speaker 02

  Yeah, this year, not a lot, because the ice has been super thick, but that's not always the case.

• 9:08Speaker 06

  Last year was definitely our busiest year, just because of the mild winter.

• 9:12Speaker 02

  Justin said that's because there were multiple freezes and thaws, which led to a particular kind of ice shelf that's super dangerous.

• 9:19Speaker 06

  When there's solid ice and then there's water on top of it, and then another ice formation forms on top of that water, so it looks like solid ice.

• 9:27Speaker 02

  But it's not solid ice at all. And a person who was walking on the ice at night fell through.

• 9:33Emily Kwong?

  Oh, gosh.

• 9:34Speaker 06

  It wasn't deep water, but the ice shelf made it so he couldn't get out of the water. So he would, he would have been gone if we wouldn't have been able to find him.

• 9:43Emily Kwong?

  Was he okay? So they got him out?

• 9:45Speaker 02

  They got him out. And in drone footage from the rescue, you can see that the ice just keeps breaking up when the rescuers are trying to get to them. And when they all get pulled off the ice, like it just keeps breaking up because of this false ice shelf that Justin was talking about. And Justin said the person was probably in the water for around 25 minutes, trying to get out of the water before they called for help, but they were okay.

• 10:08Emily Kwong?

  I'm so glad to hear they were okay because it is incredibly dangerous. I mean, falling into cold water can kill you in less than a minute. Many people die within just minutes from cold shock, so not every rescue has a good outcome.

• 10:20Speaker 02

  Yeah, unfortunately, they don't. And the frequency of both people going through the ice and people drowning from ice breakthroughs are increasing globally as climate change drives up the average temperature.

• 10:32Speaker 09

  We've documented over 4,000 fatal drownings through ice.

• 10:37Speaker 02

  This is Sepna Sharma. She's a global change biologist at York University in Canada. The drownings she's talking about were from 1991 to 2017, and they happened across 10 countries. She says 50% of those drownings are related to air temperature.

• 10:52Speaker 09

  So basically, what that means is that half of those drownings can be explained by winter air temperatures, such that in warmer winters, more people drown.

• 11:03Speaker 02

  When temperatures are hovering right around freezing and freezing, unfreezing, freezing, unfreezing, that leads to more of that weak white ice that we talked about earlier. And it's harder to tell just how safe the ice is.

• 11:14Emily Kwong?

  And not to mention riskier for people who can't judge whether they'll fall through it or not.

• 11:19Speaker 02

  Right, going out on the ice. And another thing that makes ice safety trickier to predict is something Hillary calls winter weirding.

• 11:26Speaker 05

  Well, just have these really cold polar vortex events followed by heat waves. And so winter is no longer this.

• 11:35Speaker 05

  Duration of colds, weather, it kind of bounces around all over the place.

• 11:39Emily Kwong?

  So throughout the winter, lake ice is getting more unstable, less safe. Plus, ice is forming later and disappearing earlier.

• 11:47Speaker 09

  Depending upon the extent of greenhouse gas warming, you might expect 10 to 28 days less ice cover by the end of the century. And at current greenhouse gas emission scenarios, we forecast about 5,700 lakes may permanently become ice-free within this century.

• 12:03Emily Kwong?

  Over 5,000 lakes permanently ice-free within the century? That is so many! It changes winter as we know it in the north. I guess if there is an upside, it's that if they don't freeze over, it definitely reduces the chances of people falling through. But what is that stake for the environment if all that ice is lost? Well, for starters, Sopina says,

• 12:27Speaker 09

  when you have less lake ice cover, you have less ice fishing opportunities, recreation opportunities. It matters for winter ice roads. So many northern communities, especially remote communities and many indigenous communities actually require the use of winter ice roads to access food, fuel, medical supplies, and even social connections in the winter.

• 12:50Emily Kwong?

  Yeah, ice is an invaluable resource, actually, in a lot of places. And it is being threatened by climate change. As is lake ice culture, which is less tangible in some ways, but comes with a lot of sorrow. Yeah, I bet. It's like a way of life you practice, Burley. Yeah, and James Thai, the festival organizer who we met earlier, hopes that it's also a call to action for change.

• 13:12Speaker 03

  Once people care about something, then they're going to want to protect it. You know, things are changing. And if there's a year that you can't be on the ice, then people are going to start to wonder why.

• 13:23Emily Kwong?

  And maybe they'll ask for a change. Burley, thank you so much for bringing us this reporting on changing lake ice from your neck of the woods. You're welcome. To see pictures of Burley during the lake ice rescue training or at that really cool festival, check out our show notes. Also, there's so much more reporting to come. We will have another episode on changing lake ice coming out next week. Also, follow us on the app you are listening to, please. Whether that's the NPR app or another one, it really helps us out and means you won't miss out on cool new episodes.

• 13:59Emily Kwong?

  This episode was produced by Hannah Chin. It was edited by our showrunner, Rebecca Ramirez, and fact checked by Tyler Jones. Jimmy Keely was the audio engineer. I'm Emily Kwong. Thank you for listening to Short Wave, the science podcast from NPR.

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