Wednesday, February 23, 2011

Lake Champlain 'Closed' by Ice?

This morning, while walking towards the UVM campus in single digit temperatures, I noticed something odd about the lake. It took me a minute to realize what it was, but I realized there were no little ripples or waves. None at all. There wasn't much wind at the time, but even during seemingly caml days the lake always has a few ripples on it. Also, the reflections were just a little bit weird. They seemed kind of warped and blurred.

It took me a minute to realize what had happened. The lake had frozen over. From what I could tell, the ice extended all the way across the lake.

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(Note the thicker ice in the harbor, which is much whiter because its surface is bumpy and it is covered in snow)

The conditions last night were perfect for ice formation.  According to National Weather Service records, the temperatures at the Burlington Airport were below zero Farenheit for several hours (and reached as low as -3), winds were calm, and the sky was free of clouds (as it still is as of 11:30 AM).  Colchester Reef, on the lake itself, reached 9 degrees with clear skies and 5 mile per hour winds (and presumably also clear skies).  It seems that these conditions allowed the lake to finally freeze across, albeit probably not to a very thick depth.

This graph shows some interesting things going on in the lake.  Since this sensor is near shore, the lake has been frozen at this location for a bit longer -  probably since early February when the temperatures bottomed out.  The ice must have grown thicker though, judging by the recent irregularities in data.  (the temperature of 34 degrees is not that unusual for underneath the ice of a frozen lake.  If the sensor is near the bottom of this shallow part of the lake, 34 degree water will concentrate there when conditions are calm, because this is the temperature at which water is densest.  I'm not sure why the water was colder before the lake froze all the way across though.)

When the lake is frozen all the way across, it is said that the lake has 'closed'.  This used to happen most winters, but not it usually does not happen.  This is due to average temperatures having risen a bit in the last few decades.  This winter has been below average in temperature, but the winter had to overcome a quite warm summer's worth of stored heat in the lake.  It looks like winter did win the battle this year, although I am not sure if this thin layer of ice 'counts' as a lake closing.  As of right now, I can see the lake and it looks like it is still frozen, but I can't be sure.  Temperatures are expected to rise a bit, to a bit above freezing at times, and winds are expected to pick up, so the icing over of the lake may prove to be very short lived.

Before this latest cold spell, I had guessed that the lake would not freeze across.  It came close during the coldest temperatures in late January and early February, but heavy winds just kept blowing the ice back and forth, and the lake temperatures just weren't low enough way out in the open lake.  This picture of the Shelburne Farms area shows a bunch of ice jammed in an inlet.


Oddly, this freezing of the lake comes just as the very first signs of spring are appearing.  One of the urban seeps I found last year broke through the thick snow cover and some standing water was present at the surface, unburied by snow, for the first time since the heavy snows of mid January.
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This has been a long, cold winter.  For those of you who dislike winter, though, keep in mind that these are the last few really cold weeks, and things are already turning around.  For those who love winter, on the other hand, there should be plenty of fun spring skiing soon!


  1. Hello! I can see the lake from my window and I have been waiting for the lake to close.
    I have seen it closed twice so far this winter. Once on the morning you are writing about when a thin layer froze clear across and then again on the 26th right after the big snowfall it was white all the way across. I think the 27th was warm again so it opened up a bit. I went out of town before the last big dump on March 6th - was it white all the way across on the 7th?

  2. Hey,

    Thanks for sharing your observations! It sounds like this year the lake was only able to freeze all the way across very briefly if at all. This winter was fairly cold, but my guess is the ambient warmth from a warm summer kept it open longer than it has in some past years.

    I doubt it closed on March 6th because that storm was preceded by quite a bit of rain and warm weather... it probably melted more ice than it froze. It didn't seem frozen over on the 8th when I saw it but I wasn't in town on the 7th either.