UNH research: Less snow, longer mud season could alter rivers

UNH researchers studied the spring vernal window, commonly known as mud season.

Researchers at the University of New Hampshire say a decrease in snow cover due to climate change could affect ecosystems that depend on traditional spring thaws.

“Very high river flows following snowmelt trigger some species of fish to move upstream. Cold water temperatures are required for some species of fish to spawn,” said Danielle Grogan, a scientist at UNH’s Earth Systems Research Center who studies river systems.

Using funding from the National Science Foundation, Grogan joined research assistant professors Elizabeth Burakowski and Alexandra Contosta to study the spring vernal window, commonly known as mud season.

The researchers focused on snow disappearance, spring runoff and the appearance of buds on trees.

Climate datasets that projected future temperatures and precipitation levels were used to drive simulation models to assess the shift in both the opening and closing of the vernal window as well as the effects on rivers and surrounding ecosystems from 1980 to 2099.

They determined that by the end of the century, a decrease in snow cover in northeastern North America will result in the vernal window increasing two to four weeks in many places.

Under the most dramatic model, 59 percent of land from Maine to Virginia would not accumulate any snow cover.

“An area had to have more than 20 days with at least an inch of snow on the ground during the winter to say there was snow cover that winter,” Grogan said.

The results of the researchers’ study was recently published in the journal “Environmental Research Letters.”

Losing the snow would change ecosystems and disrupt natural patterns such as migration and fish mating, according to Grogan.

She said the next step is to do more research.

“What was surprising is we saw a change in the rivers even when there was snow,” Grogan said.

Previous studies have examined how climate change will alter the vernal window, but few have explored the impacts on rivers and surrounding areas during this transitional period, according to a news release from UNH.

Meteorologists at the National Weather Service in Gray, Maine, said on Monday that normal snowfall in New Hampshire and Maine currently averages 50 to 70 inches along the coast and gradually increases inland, with more than 140 inches per year in the mountains.

The second-warmest year on record was 2019, with a global average surface temperature 1.71 degrees above the 20th-century average. Nine of the 10 warmest years on record have occurred since 2005, according to officials at the National Oceanic and Atmospheric Administration.

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