Historically, Lake Superior did freeze over entirely. The current open 
water during winter allows for much greater evaporation that would occur 
if the ice cover were 100%. One of the major contributors to the drop in 
the level of the Great Lakes is the additional winter evaporation 
associated with the reduction/absence of ice cover.
Lakes Seneca and Cayuga are oriented somewhat in the direction of 
prevailing storms. In winter the temperature of both lakes is within 
0.1C top to bottom as a consequence of mixing of water from top to 
bottom related to prevailing winds. For both lakes to freeze at the top 
for the entire length, it would be necessary for the entire water column 
to loose enough heat to be very close to 0C. As long as the power plant 
continues to release a great deal of heat to the surface, Cayuga Lake 
will never freeze 100%, even without any effect of global climate change.
The concentration of redheads in Cayuga Lake is a consequence of keeping 
some shallow areas open due to water movement from the deeper areas that 
don't freeze. Other, shallow lakes in this area do freeze over 100% so 
that there is no way that diving ducks can get food.
(PS: This may seem odd coming from a birder, but my grad work was in 
limnology with half the research since grad school was on lakes.)

John Confer

On 2/9/2014 7:20 AM, Liisa S. Mobley wrote:
> There's been a bit of discussion about the Finger Lakes freezing over, as 
> well as the Great Lakes, on the Cayuga Birds list in recent weeks.  I came 
> across this article from one of the channel 9 (Syracuse) weathermen, which 
> indicates that the Great Lakes, as of last Friday, had more than 79% of their 
> surface area frozen.
>> Great Lakes Freezing Over: Dave Eichorn's Blog
>> http://bit.ly/1gcubdX
> Where do all the birds go?  Lake Ontario is only about half frozen, so maybe 
> they go there.
>
> You'll notice in the photo that Cayuga and Seneca are not frozen.  Not sure 
> why they don't freeze over, too.  And, no, they are not deeper than the Great 
> Lakes, except for Erie.  (This is kind of bugging me, so let me know if you 
> have a good answer!)
> -Liisa
>
> Liisa Mobley
> Sent from my iPhone
>
>
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