PORTLAND – A new study shows the average thickness of winter ice has decreased on the Piscataquis River, adding to a growing body of evidence that the region’s winters are less severe than in the past.

Previous studies of river flows, ice melt on lakes and sea-level changes also point toward a potential warming trend in the region.

The new study by the U.S. Geological Survey published in the journal “Climatic Change” found that ice on Piscataquis River in late February became thinner by an average of 9 inches during the 20th century.

During that time, the average surface air temperature rose by about 3 degrees, said Thomas Huntington, the lead author.

“The hydrological data clearly supports the environment in Maine, and New England in general, experiencing a warming in late winter and early spring,” Huntington said from his office in Augusta.

Huntington was joined by Glenn Hodgkins and Robert Dudley, also of the U.S. Geological Survey, on the latest research.

They focused on a location on the Piscataquis River near Dover-Foxcroft because there was plenty of data and the river flow was relatively unfettered by dams or other human influence.

There also was a wealth of information including analyses of river flow and the timing of ice-out, Huntington said.

In addition to the river ice thinning by 9 inches – or 45 percent – from 1912 to 2001, there was a gradual shift in river flow that pointed toward snowmelt that was 10 days earlier than in years past, he said.

The report also looked at 35 years of data that showed a warming trend on the Wild River near Gilead and 25 years of data that showed earlier fish migration from the ocean to rivers in Maine, he said.

The scientists report that their findings were consistent with other trends toward shorter winters: earlier melting of frozen lakes, earlier lilac bloom dates and earlier warming in the spring.

Two years ago, a team of international researchers using new dating techniques on salt marsh sediments reported that the sea level has risen between 12 and 20 inches along Maine’s coast over 250 years.

As a whole, the data points toward climate change, Huntington said.

“Clearly, the physical and biological systems are sensing the difference, and I think the data is overwhelming in that [the climate] is warming,” he said.

The research does not point toward any specific causes of the trend. And it doesn’t link the warming in New England to trends elsewhere.

Greg Zielinski, Maine’s state climatologist, said he doesn’t take issue with the research, but he urged caution in jumping to conclusions because Maine’s weather is highly variable and instrumental records are inconsistent.

While the latest research points to warming in Maine, Zielinski said some data suggests the climate has actually cooled, especially in northern Maine. He said the truth may lie somewhere in between.

“There have been some warmer winters recently, but there’s a lot of variability,” said Zielinski, a professor in the University of Maine’s Climate Change Institute. “We could easily begin seeing some colder winters.”