Most of the popular discussion about the changing climate focuses on summer conditions including the increased potential for drought and extreme heat, yet winter conditions are changing most rapidly in the Northeast. Two studies led by a University of New Hampshire scientist provide an overview of a dozen key signs of changing winter conditions across the region that could have lasting impacts on ecosystems, water supplies, the economy, tourism, and human health.
“Whether precipitation falls as snow or rain makes a big difference, whether you’re talking about a forest stream, a snowshoe hare, or even a skier,” said Alexandra Contosta, a research assistant professor at the UNH Earth Systems Research Center.
Contosta and her colleagues examined 100 years of winter temperature and precipitation data from weather stations across the forested parts of the Northeast, eastern Canada, and Great Lakes region. They found, for example, that there are now fewer “ice days” when daytime temperatures never go above freezing; fewer “frost days” when nighttime temperatures dip below freezing; and fewer days when temperatures sink below 0 degrees. The northern forest has also lost 19 days of snow cover compared to a century ago, and the cold period of the year is now three weeks shorter than it used to be. The implications are significant.
“A lot of ski areas depend on snowmaking because we’re losing a lot of natural snow. But to make snow, you have to have the right temperature conditions, and we’re losing those nights that are cold enough to make snow. We’ve lost 16 days of snowmaking before Christmas. That impacts skier visitation, which is important for many rural economies,” Contosta said. “And a lot of forest harvest occurs in the winter, particularly at bottomland sites that are difficult to access in winter, so they might have to change the timing of the harvest in some cases.”
A shortened winter means expanding ranges of disease-carrying ticks and invasive mosquitoes. It also means that more tree-killing pest insects such as the hemlock wooly adelgid and pine bark beetle will survive the winter. In addition, reduced snow cover has negative implications for the forest ecosystem, because snow provides an insulating blanket on top of the soil and shrubs or fallen trees that serve as important wildlife habitat for ruffed grouse and other animals.
“It’s important to realize that these warming trends aren’t going away unless we do something to slow the effects of climate change, and that takes political will,” Contosta said. “There are adaptation measures we can take, but it also comes down to slowing the warming trend.”
The next step in the study is to apply the key indicators to future climate projections to see how winter conditions are likely to change in coming years.
“We’re also interested in trying to see if there are ways to conserve or manage parts of the forest for coldness,” she said. “Are there locations on the landscape that are more likely to retain cold conditions and keep snowpack for longer, and can we preserve those areas or manage for them as islands of coldness?”