24 November 2010

Making Ice

A low of 7 degrees and a wind yesterday morning aided in removing the last bit of warmth 
off the top layer of water in Wayzata Bay.  

According to the DNR: "Water is most dense (heaviest) at 39º F (4º C) and as temperature increases or decreases from 39º F, it becomes increasingly less dense (lighter). In summer and winter, lakes are maintained by climate in what is called a stratified condition. Less dense water is at the surface and more dense water is near the bottom.
During late summer and autumn, air temperatures cool the surface water causing its density to increase. The heavier water sinks, forcing the lighter, less dense water to the surface. This continues until the water temperature at all depths reaches approximately 39º F. Because there is very little difference in density at this stage, the waters are easily mixed by the wind. The sinking action and mixing of the water by the wind results in the exchange of surface and bottom waters which is called 'turnover'."

Last look at open water in 2010

19 November 2010

Tundra Swans

Tundra swans were flying over the Twin Cities tonight on
their way to their Mississippi River resting stop 
near Brownsville Minnesota just north of the Iowa border.
Here is a video taken last November showing the river view
with the sights and sounds of the swans as well as
other ducks and bald eagles.
It is truly a magnificent annual migration scene
that is successful due to habitat restoration on this 
portion of the Upper Mississippi.