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Merrimack Valley

February 16, 2014

Merrimack River's historic freezing patterns pose scientific questions

Scientists have some theories but no explanation behind river's freezing patterns

NEWBURYPORT — There’s a curious photo in the city’s historical archives that captures a moment literally frozen in time.

It’s the winter of 1897, and nine men stand on the Merrimack River, a few dozen yards offshore from what is now Newburyport’s downtown waterfront boardwalk. The photographer is much further out on the ice -- perhaps 200 feet or so.

The photo shows something that was once a fairly frequent natural phenomenon, but hasn’t happened in decades. The Merrimack River used to freeze so solidly that horses and sleighs could safely cross it from Newburyport to Salisbury. People would walk from one side to the other, over a thick sheet of solid ice.

No one would dare try such a thing today. It’s impossible. Even in bitterly cold winters there’s always open water near downtown Newburyport, and the ice on the river’s edge is thin and dangerous to walk on. Our lower end of the river no longer freezes all the way across.

What’s changed?

It’s a question that the experts can’t answer definitively. There are a number of possible and interesting culprits, nearly all of which reflect the incremental changes that mankind has made on the local environment. Add them all together, and it’s clear that this is a very different river than the one that Newburyport’s citizens knew a century ago.

“It’s hard to pinpoint why the river isn’t freezing anymore,” said Roy Sokolow, a hydrologist for the United States Geological Service’s Massachusetts Water Science Center. “You can make some assumptions, but I don’t like to make assumptions without data.”

This year there’s an anomaly that has made it impossible for the river to freeze across. The work on the Interstate 95 bridge project has brought with it icebreaking boats that are cutting through the ice on a daily basis. But that anomaly aside, observers say its clear that the overall pattern is less ice in the Merrimack, particularly at this lower end.

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