Thursday, March 11, 2010

How is this possible?

In 2004, we had a prodigious snowstorm in Seattle.  In fact, it snowed so hard and so fast that there was snow floating on top of the seawater in Eolian's slip.

At first glance, this looks like ice floes, but it was not.  A quick probe with a boat hook showed that it was actually slush cakes.

So, how is this possible?  This is, after all, seawater, and at a temperature of something like 45 °F to boot. 

My theory is that the snow fell fast enough that a layer of fresh meltwater formed on top of the salt water.  Because fresh water is less dense than seawater, that arrangement was stable.  And because the water came from melting snow, it was cold.  Add enough snow, quickly enough, and the water would be near 32 °F, cold enough for slush to be stable.

And it was stable - the snow "floes" lasted for more than an hour.

That's my theory anyway.  Maybe one of you from a cold weather port can substantiate it, or debunk it.

And why am I posting this just now?  Because winter has returned to Seattle, at least for now.


SV Estrellita 5.10b said...

We were stuck up in Princess Louisa Inlet because of ice in January 2009. The freshwater not because of snow of course, but because of the falls.

bob said...

Perhaps that played a part here too... Shilshole is right at the exit of the Ship Canal, which is a fresh water discharge. I know there is fresh water mixing with the salt in the marina, because I can see the index of refraction changes from the mixing when I dive on the prop.

But I have only seen the "snow floes" once.

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