The winter-old river ice is creaking and groaning, shifting position. Spring has come early to the frozen upper Hudson River, and ice-out is just around the corner.
Lilliputian wildflowers will soon line the Hudson's banks. In what are known as riverside ice meadows, an ancient cycle of ice formation and melting gives rise to swamp candles, ladies'-tresses, wood lilies and other rare, diminutive flowers.
In New York's Adirondack Mountains, ice that forms on the river in winter is pushed onto its banks in spring; there it scours the sloping cobble shores, keeping them free of shrubs and small trees and leaving space for wildflowers to sprout in fragile, arctic-like ice meadows.
But the future for these floral pixies, which depend on late-melting river ice, is bleak. The number of days of ice on northeastern rivers has declined significantly in recent winters, said hydrologist Glenn Hodgkins of the U.S. Geological Survey Maine Water Science Center in Augusta.
The trend could spell disaster for the ice meadows. It also signals trouble ahead for endangered Atlantic salmon and other fish, for wetlands plants and animals, and for Northern economies, all of which are sustained by winters with icy rivers.
If the pattern continues, say scientists, only in Currier and Ives prints will ice skaters twirl across frozen New England rivers.
"Northeastern rivers have 20 fewer days of ice cover each winter now than they did in 1936," said Hodgkins, who said the total now averages 92 days. "A lot of that decrease has occurred since the 1960s."
Hodgkins has studied 16 rivers in Maine, New Hampshire and Vermont. In recent years, the data show, 12 of the 16 rivers had much earlier spring ice-out dates.
"On average, ice-out dates were 11 days earlier in 2000 than in 1936," Hodgkins said. "These changes are linked to warmer temperatures in late winter and early spring."
Winter, it appears, is melting around the edges.
Research by Hodgkins and USGS scientist Robert Dudley also shows changes in early-spring stream flow across eastern North America from Minnesota to Newfoundland. Rivers are gushing with snow- and ice-melt as much as 10 to 15 days sooner than they did 50 to 90 years ago, based on USGS records.
Hodgkins and Dudley's results are scheduled to be published Tuesday in the online edition of the journal Geophysical Research Letters.
The Maine Water Science Center, where Hodgkins works, is two miles from the Kennebec River.
"In 20 years here," said Andrew Cloutier, another researcher at the center, "I've never seen the river this ice-free." Scientists usually retrieve samples of river water in winter by drilling through ice that's several feet thick. "But not this year," said Cloutier. "We were out there in open water in hip waders."
End of ice fishing?
Hydrologists weren't the only ones in hip waders, said Jim Worthing of Randolph, Maine, who rents huts to ice fishers who, most years, set them out on the surface of frozen rivers to catch smelt. "This season I had to put the huts on floaters [floating platforms] and pull them out into the river so people could still fish," he said.
Smelt fishing, a popular rite of winter in Maine, "starts as soon as ice forms on rivers," Worthing said. Smelt are anadromous fish, hatching from eggs in rivers and then migrating to ocean shallows, where they spend their adulthood before eventually returning to fresh water. The fish begin moving upriver in December, where the ice fishers await them.
"Not so this winter," Worthing said. "I'm beginning to think it's the end for ice fishing on rivers here. But never mind us -- who knows what it's doing to the smelt?"
Plenty, if the work of biologists such as Joan Trial is any indication.
"Lack of ice on rivers severely affects fish, especially anadromous fish like endangered Atlantic salmon," said Trial, a biologist at the Maine Atlantic Salmon Commission in Bangor. "Ice cover insulates rivers and streams, protecting young salmon from cold. Without that cover, the salmon are also more susceptible to predators." Bald eagles, for example, are able to snare their piscine prey only from open water.
Atlantic salmon are in peril for several reasons, but scientists Terry Prowse and Joseph Culp of the National Hydrology Research Center of Environment Canada in Saskatoon, say lack of river ice has the potential to kill large numbers of salmon eggs, as well as juvenile and adult fish.
The most difficult winter situation for salmon and other fish, biologists say, is on-again, off-again ice cover: rivers that freeze over one week and then are open the next.
"Fish expend critical energy responding to these unstable conditions," Trial said. Ice that doesn't stay frozen may also contribute to the deaths of aquatic animals such as northern leopard frogs, which overwinter far beneath a chilled-to-freezing blanket.
"The reduction in river ice between January and April has important ecological effects," Hodgkins said, "including more frequent formation of 'anchor ice.' " Anchor ice, a spongy, smothering type of ice, covers the bottom of a river instead of "floating" on top, but it can't form when the surface is already frozen, he said. "Anchor ice slows down or eliminates water flow near the riverbed, which leaves fish embryos starved for oxygen."
When river ice finally breaks up in spring, the process results in what's known as ice-jam flooding: water spilling over the banks behind piled-up ice. Ice-jam flooding, say Prowse and Culp, is the main way water levels are sustained in ponds and wetlands alongside rivers. Without this flooding, habitat for migrating waterfowl and aquatic mammals such as beavers and mink often disappears. If there is not enough ice during winter, wetlands can quickly become dry lands when spring arrives.
Signs of such wetlands changes are starting to appear, said Scott Longfellow, owner of Longfellow's Greenhouses in Manchester, Maine. "People are asking why they're already seeing pussy willows along rivers and streams," he said. "Pussy willows, which grow only where it's wet, come out long before crocuses and snowdrops. I tell customers that ice-out must have happened by now on their wetland, then -- or that there wasn't any ice there this winter."
Three hundred miles inland along the upper Hudson River, on this first day of spring, it's the same story. The ice meadows are usually still under several feet of ice, but this year it has already broken up.
If the trend continues, say scientists, the wood lilies and ladies'-tresses may soon be gone in the warming winds.