The warmest winter on record has melted the spirits of ice-fishing and skating enthusiasts in Vermont and New Hampshire, shattering early ice-out records on lakes, some by a few days, others by nearly a month. The most recent was Lake Winnipesaukee, New Hampshire’s largest lake, which experienced its earliest ice-out in history Sunday, beating the record set in 2016.
But a more pressing concern, officials say, is the detrimental effect this premature thawing of the ice cover is having under the surface.
Mark Mitchell, a freshwater scientist and partner for the Vermont Department of Environmental Conservation and the University of Vermont Lake Champlain Sea Grant, said early ice-out conditions — the period when lakes are free from ice — are “concerning” for the lakes’ ecosystem. Early melts and warmer water mean a longer period for plant growth and the proliferation of invasive species and cyanobacteria (blue-green algae) blooms.
“Warmer winters and warmer summers definitely raise alarms a little bit,” Mitchell said.
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Normal ice-outs have typically occurred during the first half of April, according to experts. The Lake Morey Protective Association in Vermont reported that its lake in Vermont was clear of ice on March 14, the earliest ice-out on record since it started keeping data in 1977.
Bill Minard, a member of the association, said this winter’s thinning ice led to the cancellation of the annual pond hockey tournament earlier this year and limited skating over the past few years.
“The early ice-out has shortened the ice fishing season as well,” Minard said. “Of course, these are all recreational endeavors. Our concern is for our Earth, the impact on the natural world, and those who are facing dire consequences, those living on islands and shorelines.”
Christopher Conant, president of the Lake Iroquois Association, said the lake in Hinesburg, Vt., had record-breaking ice-out on March 7, breaking the mark set on March 9, 2000.
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Like others who have made life near the lake their home, Conant said he’s equally concerned about effects early ice-outs have on lake ecology. A longer growing season can give aggressive invasive plants, such as the Eurasian water milfoil, a chance to blanket bodies of water like Lake Iroquois from shore to shore, according to officials. EWM can form large mats of floating vegetation that shade out large plants and impede recreation. EWM can affect lakes regardless of the size of the water body.
“The greatest concern of this invasive species is on native aquatic plant diversity,” Conant said. “Besides the ecological impacts, infestations of milfoil have economic impacts through the reduction of property values and the high costs of various treatment options.”
These shifts in our lakes emphasize the need for protection and preservation of our water bodies now, according to Bree Rossiter, the Lake Winnipesaukee Association’s conservation program manager.
“These changes in water temperatures can significantly impact the lake’s ecology, benefiting some species but negatively impacting others, such as cold-water species like landlocked salmon and trout,” Rossiter said.
Earlier than usual ice-outs this year
• Lake Winnipesaukee – New Hampshire’s largest lake experienced its earliest ice-out in history Sunday, beating out by one day the record set in 2016.
• Lake Willoughby – Vermont’s deepest lake is free of ice for the first time in March (records date back to 2018).
• Lake Iroquois in Vermont – Ice-out was on March 7 this year, breaking the record set on March 9, 2000.
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• Lake Sunapee in New Hampshire – Officials say ice-out is getting close.
David Neils, chief aquatic biologist for the New Hampshire Department of Environmental Services, said its staff typically begins monitoring ice-outs in mid-April but began sampling last week. He said ice-out dates over the past 80 years or so are “two-three weeks earlier than in the past.”
This past season, eight northern US states, including Vermont and New Hampshire, recorded their warmest winter yet – from Dec. 1 to Feb. 29 (meteorological winter) – in line with the warmest-ever average temperatures reached across the entire contiguous US this past winter.
According to Globe meteorologist Ken Mahan, New Hampshire smashed its temperature average for winter by 6 degrees with a 28-degree winter. Burlington, Vt., was 11 degrees above average this winter, and Concord, N.H., was 10 degrees above average. Massachusetts had a winter average of 33.5 degrees, just short of the 33.7-degree winter average record set in 2016.
Mitchell said more research is needed on the effects of early ice-outs.
“We just know that the ecosystem is used to these normal cycles with sun variation,” he said. “Climate change, in general, is changing the natural cycles of the ecosystem and different species are moving up north. Some species are pushed out and have to change behaviors in the lake environment. The warmer water temperatures mean longer and longer growing seasons for algae and plants.”
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Carlos Muñoz can be reached at carlos.munoz@globe.com. Follow him @ReadCarlos and on Instagram @Carlosbrknews.