Ice Out: How N.H.’s rite of spring has become a symbol of climate change

For the past few weeks, Dave Emerson has been taking off from his airstrip on the southern side of Lake Winnipesaukee, flying his Cessna across this largest lake in New Hampshire, and looking – very carefully – for ice. 

As of last week, it was almost gone. But not quite. Not enough to call “Ice Out,” that magical moment when the MS Mount Washington, the 230-foot excursion vessel that’s been transporting tourists on this lake since the 1940s, is able to reach every one of its five ports. Center Harbor, the town on the northern fingers of the “Big Lake,” as people here call it, was still iced in. There were chunks still floating in the town of Wolfeboro’s harbor to the southeast. But it was only a matter of days that the lake would be clear, and Mr. Emerson, owner of Emerson Aviation, pledged to the many, many people following his updates that he would keep flying, multiple times a day, and would let them know as soon as the moment arrived – the way he has been doing since 1979.

Much, after all, is riding on Ice Out. Restaurants, rotary clubs, and town chambers of commerce distribute thousands of dollars to raffle contestants who most accurately guess its date and time. The New Hampshire Boat Museum holds an annual Ice Out Celebration (virtual, this year, scheduled for April 16). And for those who live here, Ice Out means that spring is actually around the corner – that it’s time to replace snowmobiles and bob houses with hiking boots and sailboats. 

“It’s the changing of the seasons,” says Martha Cummings, executive director of the boat museum. “The ice is gone, boaters can get back on the water, spring is on its way, and we can all get out of our houses and go outside again.”

But to scientists who study lake ecosystems, Ice Out means something even more. Ice is a key player not only in the culture of the northern Northeast, but also in its unique lake ecosystems – a determinant of everything from water temperature to aquatic food chains to water quality. And according to long-term climate data, ice-out has been moving earlier and earlier – a sign, scientists say, of warming winters in New Hampshire and the Northeast as a whole. 

“For us in New England, winter is the fastest-changing season,” says Alix Contosta, an ecosystem ecologist with the University of New Hampshire’s Earth Systems Research Center. “We’re seeing the biggest changes in temperature in winter as compared to the rest of the year. ... We are losing the cold.”

Over the past century, Dr. Contosta and other researchers have found, New Hampshire as a whole has lost 21 days of annual snow cover. The average annual temperature in the state has increased 3 degrees since the beginning of the 20th century, according to the National Oceanic and Atmospheric Administration, and research shows that there are 18 fewer days now when the nighttime temperature drops below freezing than there were a century ago. Fewer places in the region have 30 days of continuous snow coverage. 

Bigger extremes

“Rain on snow” events are far more common (as those who must plow their driveways can attest), as is intermittent melting, says Brenda Ekwurzel, senior climate scientist and director of climate science with the Union of Concerned Scientists. The warmer temperatures also lead to more moisture in the atmosphere, she says, which in turn creates heavier snows and rainfalls. Indeed, she says, the most extreme precipitation events – those big snow and rain storms – contain 50% more water volume now than they did in the 1950s. 

“The characters of winter are changing,” Dr. Ekwurzel says.

And so, she and others say, are the lakes. 

For more than 50 years, Gene Likens, founding director of the Cary Institute of Ecosystem Studies and special adviser on environmental affairs at the University of Connecticut, has recorded detailed observations about the ice cover on Mirror Lake, in the southern White Mountains of New Hampshire.  

There, scientists call ice-out when less than 50% of the surface water is frozen, explains Tamera Wooster, a technical staffer who works with Dr. Likens at the Hubbard Brook Ecosystem Study, a multidisciplinary, long-term ecological study that includes Mirror Lake.  

She’s the one whose job it is to say when that happens, so this time of year she drives regularly to different points on the wind-swept shoreline and looks. 

As of last week, the bob houses were gone – ice fishers have an astute sense of when their sport should end for the season, she says – but the lake’s surface was still almost all ice. 

Still, that ice was thin. 

“It would only take a couple of sunny days and a rainstorm and we’re out,” she says. 

On average, Dr. Likens has found, the ice cover on Mirror Lake lasts for approximately 21 fewer days than when he started recording it in 1967. That is similar to what has happened at other lakes throughout the region, although the pattern is not linear. 

Indeed, a graph on various lakes maintained by the New Hampshire Department of Environmental Services shows a downward-sloping fan of ice-out dates, as the year moves from the 1860s, when ice-outs were first recorded, to the present. During the 1990s, some lakes lost their ice covers as early as the beginning of March, an unprecedentedly early ice-out. Other years saw the typical late April and early May melt. 

Ecological effects

This erratic pattern is what scientists say they see regularly with climate change. There are new extremes, with the overall trend being a warming one. 

And that, Dr. Likens says, has a slew of ecological impacts. An ice cover on a lake not only seals off the water from wind and circulation, but also creates a platform for snow, which then reflects the sun. Conversely, a dark surface, such as open water, or even a leaf resting on a piece of ice, will absorb much of the sun’s heat – a smaller version of what many climate scientists talk about when it comes to the accelerating heating cycle of the polar ice melts. 

The northern lake ecology is tied to this balance of having a cold, reflective surface for part of the year, and a heat-absorbing one for the rest. When ice-outs come early, the water temperatures rise; this, in turn, creates better habitats for algae and, scientists believe, cyanobacteria – a type of single-celled organism that can harm other animals. Early ice-out can also affect the way a lake’s water mixes, and its oxygen levels.

“Ice, for a lake, is very, very important for setting the summer conditions,” says Dr. Ekwurzel. “What the fishing conditions are, what the oxygen levels are, the amount of nutrients that might be running off agricultural land.”

Some worry that early ice-outs could be changing winter culture in what’s known as New Hamsphire’s Lakes Region. The Alton Bay Ice Runway, which advertises itself as “the only plowed ice runway in the Continental US (that we know of!),” was only open for two weeks this year, after not being able to open at all in 2020. Ice boaters, whose sailing crafts on metal runners depend on solidly formed ice, have told Ms. Cummings, from the boat museum, that their seasons are shorter. 

“Our boating community has noticed the difference,” she says.

“An opportunity to learn more”

But this difference, says James Haney, a professor of biological sciences at the University of New Hampshire, can be an invitation for curiosity as much as concern. 

“I think the climate change and ice-off is generally looked at as a harbinger of bad news,” he says. “I look at it as an opportunity to learn more.”

To others, the ice fluctuations are just another example of the weather surprises that New Hampshire has always thrown at them. 

“Tell me a time climate hasn’t been changing,” says Mr. Emerson, who was heading up one more time to see if he could make his call.

Based on what he saw, he expected ice-out on Winnipesaukee would come soon. And indeed, at 4:42 p.m. on Monday, he was able to make his call.

“It’s official!” he wrote on his Facebook post, which has since been shared more than 1,300 times. “Welcome to Spring in NH.”

Mr. Emerson would not enjoy any of the raffle winnings, though. He doesn’t make predictions about ice-out, even though he gets a lot of inquiries.

“Someone would be calling it fixed,” he says. “I stay away from all the contests.”

Mirror Lake was not far behind. Ms. Wooster called ice-out there on Tuesday – a week earlier than average.