ONCE IS A LIFETIME (Crater Lake froze over in 1924 and 1949)
The answer to the question about why Crater Lake rarely freezes
completely over, even when it gets very cold, has to do with two
(1) The extreme depth of the lake, which stores the heat input
from the summer,
(2) The high winter winds, which provide the important energy
needed to mix the colder but less dense waters at the surface with
the more abundant, deeper, slightly warmer, and more dense water
of the lake.
In the winter, in the absence of wind, the lesser dense cold water
near freezing rises to the surface and the more dense surface water
at 38 to 39 degrees F. (3.5 to 4 degrees C) sinks towards the
bottom of the lake.
Scientific studies show that below a depth of about 820 feet (250
meters), most of the lake’s water remains at a temperature near
38.3 degrees F (3.5 degrees Celsius) all year round. During the
winter, the top 330 feet (100 meters) remains at a temperature
near 37 degrees F. (2.7 degrees C).
All it will take is one very cold windless night, and the lake will
begin to freeze. If it snows the next morning, or if it’s cloudy
without sun, the ice will continue to form, provided that there’s
no wind or that a veneer of ice has completely covered the lake,
eliminating wind as a factor.
Otherwise, in the presence of direct sunlight, the clear thin ice
layer will act like a lens. Penetrating sunlight will warm the water
underneath the ice, causing the thin layer of ice to melt from below.
If a layer of snow covers the ice, the sun will have little effect
on the water below the ice, and as long as it remains cold, ice will
continue to form.
However, as long as the ice does not cover the entire surface of
the lake and water is exposed to the air, the wind will do its part
to keep mixing warmer deeper water with the colder water of the
lake’s surface to prevent more ice from forming, and melting any