Saturday, January 25, 2014

Frazil Report

It's been snowing and blowing all day today, but such a fine dry snow, there's only an inch or two or three to show for it. But I'll take whatever we can get and be glad for it.  At least the temperatures are growing more bearable, so I'm hoping for a splendid hike in the mountains at Moreau tomorrow.  It was still very bitter cold yesterday when I drove up along the Hudson north of Warrensburg to check on the frazil ice now jamming the river.  I could hardly stand to take my hand out of my mitten to take these photographs, but I do like to have a record of how the ice is behaving each year.  Because frazil ice is formed when droplets of super-cooled water are tossed into sub-freezing air, the colder the air, the more the frazil.

As this photo taken along Golf Course Road shows, the river valley is filling up fast, although the ice is still below the height it reached last year, when it pressed against the guardrail here and threatened to spill onto the road.  I have scrambled down this steep bank in summer to explore the flora along the shore, and I can attest that those ice heaps are now at least 12 feet above the normal course of the river.

As I drove north, the river disappeared from my view for a while, and by the time I could see it again from the road, I saw it was open and running swiftly, although sloshing noisily with slushy mats of frazil ice.  Eventually, this slushy ice will be stalled by the jammed-up ice downstream.  If it stalls long enough, the ice will grow downward, eventually reaching the river bottom and damming the flow completely.  That's when the ice will rise and be deposited on the shore.

When I reached the Rte. 28 bridge across the Hudson at The Glen, I could actually watch the frazil being formed in the turbulent rapids just upstream.

To my surprise and delight, I found my friend Evelyn Greene also there on the bridge, and despite our shivers, we had a grand time observing the behavior of this particular form of ice.  Evelyn has studied this phenomenon for many years and certainly knows more about it than anyone else I know.  On this occasion, she pointed out to me how the ice was being pushed together through a narrow channel to form large mats, like the one photographed here.

As the river widened, we noted how the large mats always broke up into smaller pieces as they coursed rapidly downstream.

There they go!

On my return home, I took the road that follows the opposite bank, stopping at a point we call Snake Rock to observe the piles of frazil towering over the side of the road.  Last year, the ice completely covered the road to a height of over 12 feet, requiring several weeks of work to make the road passable once again.

I could see that the frazil had crossed the road this year as well, to the point where the river appears to have flooded this low area. So far, anyway, the plows have managed to keep the road clear of frazil ice.


suep said...

frazil-mats !

I would have loved to join you and Evelyn on Friday, but alas I was needed at work, at the same time you guys were out on that bridge freezing your noses - brr I remember that last year, hope there is still some frazil-ing time left to this year!

The Furry Gnome said...

That's fascinating. We don't seem to have anything like that, the rivers all just freeze and get covered in snow. I'm going to have to watch more closely and see what I can find.

catharus said...

Simply amazing!