JUANA SUMMERS, HOST:
More than a thousand people gathered last month on frozen Lake Mendota in Madison, Wisconsin, for a celebration of winter. NPR's Berly McCoy was there and explains how a change in climate is affecting life above the ice.
BERLY MCCOY, BYLINE: Every February, Hilary Dugan looks forward to one particular day.
HILARY DUGAN: So we're standing on a frozen lake. There's hundreds of people standing out on the lake ice right now.
(SOUNDBITE OF ROCKY ORCHESTRA'S "GONNA FLY NOW")
UNIDENTIFIED PERSON #1: It's a beautiful Saturday we got here on the lake in Mendota, everybody. It's 11 degrees.
MCCOY: She's at the Frozen Assets Festival, a celebration that fosters appreciation for lakes in the colder months.
DUGAN: I like to think of lakes as public land in the winter.
MCCOY: Skydivers glide past giant, colorful kites. At 10 a.m., racers take off...
UNIDENTIFIED PERSON #2: Three - skaters first - two, one. There we go.
(SOUNDBITE OF AIRHORN HONKING)
MCCOY: ...To skate, run, walk or ski a 5K that takes place solely on the ice, dogs and kids in tow.
(SOUNDBITE OF ICE SCRAPING)
MCCOY: The ice is strong - over a foot thick.
(SOUNDBITE OF DOG BARKING)
DUGAN: You can put a bunch of transport trucks out here today and be fine.
MCCOY: But Dugan says two years ago, festival organizers were unsure if the ice on the lake was safe enough for the event.
DUGAN: So the festival on the ice was canceled, and it was sort of moved to the shore. It was still fun. You know, we still had a lot of the same things. But, you know, it takes away the spirit of what this festival's about.
MCCOY: Dugan works at the University of Wisconsin-Madison as a limnologist - someone who studies inland waters. She's trying to understand how lake ice is changing in the region.
DUGAN: So climate change is certainly affecting winters in Wisconsin and the Midwest in general. It's the fastest-warming season here.
MCCOY: She says Lake Mendota is freezing later and thawing earlier. The ice-capped season is about a month shorter than it was back in the 1850s. And this is a global trend, one that makes it hard for people who need lake ice to fish for food or rely on ice roads to bring in supplies. Along with a shorter ice season, Dugan says winters are also getting weirder.
DUGAN: We'll just have these really cold polar vortex events, followed by heat waves. It kind of bounces around all over the place.
MCCOY: Those fluctuations can affect the safety of the ice itself because it changes how the ice freezes. Typically, when the air temperature drops enough to freeze the top of the lake, water then starts freezing downward, forming what's called black ice.
DUGAN: And black ice is really strong, and it's what freezes in the lake water itself. 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.
MCCOY: And weak ice is less safe. Justin Tews knows the consequences of unsafe ice.
JUSTIN TEWS: Last year was definitely our busiest year just because of the mild winter.
MCCOY: Tews is a firefighter in Madison at Station 1, which doubles as the city's lake rescue team. One call from last year stands out in his mind. Someone had fallen through an ice shelf - a false ice layer over water that all sits above the thicker lake ice.
TEWS: It wasn't deep water, but the ice shelf made it so he couldn't get out of the water, so he would have been gone if we wouldn't have been able to find him.
(SOUNDBITE OF ENGINE STARTING)
MCCOY: As part of their training, the team drives to frozen Lake Monona, to the spot where the Yahara River flows into it. This is where they practice rescues. Tews is in a thick, bright-yellow immersion suit which will protect him from the frigid waters.
All right. How you feeling? How many times have you done this before?
(SOUNDBITE OF WATER SPLASHING)
TEWS: I can't even count. Feeling pretty good. Yeah. The ice is good. It's warm out. It's warm-ish (ph) out.
MCCOY: It's literally below freezing, by the way. He slips off of the edge of the ice into the water. Another team member approaches with a bright-yellow rescue sled and hoists Tews up using a built-in pulley system and flags the shore team...
(SOUNDBITE OF WATER SPLASHING)
MCCOY: ...Who start pulling on a rope that's attached to the sled.
How you feeling?
TEWS: Rescued. Feeling alive.
MCCOY: Madison isn't the only city seeing increases in people falling through the ice due to changing ice conditions.
SAPNA SHARMA: In the past 25 years, lake ice loss is at rates about six times faster than any other quarter-century period over the last 100 to 200 years.
MCCOY: Sapna Sharma is a global change biologist at York University, who studies changing lake ice globally. Her team looked at 4,000 through-ice drownings over a 26-year period, and they found about half of them could be explained by warmer winters. Along with safety concerns, Sharma says less ice threatens many Northern communities' ways of life.
SHARMA: 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.
(SOUNDBITE OF COWBELLS RINGING)
UNIDENTIFIED PERSON #3: Yeah.
MCCOY: Back at Frozen Assets, Hilary Dugan says, festivals like these become part of the community's identity.
DUGAN: It's just part of life here. Part of the seasonal swings of life is having the lakes freeze. I foresee in my lifetime, certainly, a winter when Mendota doesn't freeze.
MCCOY: But for today, the sun is shining, and the ice is thick. Berly McCoy, NPR News.
(SOUNDBITE OF MAZZY STAR SONG, "FADE INTO YOU") Transcript provided by NPR, Copyright NPR.
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