Wednesday, February 10, 2010

LAKE ICE: Ice Formation

I could not find any reference to blue ice but this is what I found for black ice and white ice.... There might be a quiz!

Lake ice occurs primarily in the Northern Hemisphere, where most of the ice is seasonal: it forms in the autumn, thickens during the winter and melts in the spring.

Meteorological factors such as air temperature, precipitation, wind speed and radiation balance coupled with physical characteristics of the lakes and ice (lake area, depth, volume and fetch; snow depth; ice thickness, type and albedo) lead to complex interactions and feedbacks that affect the timing of freeze-up and break-up (ice cover duration) each year.

In general, there are two types of lake ice. They are:

Congelation Ice (black ice) forms as water freezes on the bottom of the ice cover and the latent heat of crystallization is conducted upwards through the ice and snow to the atmosphere. Its growth rate is proportional to the rate at which energy is transferred from the bottom surface of the ice layer to the air above.
Congelation ice is often referred to as black ice because it has a high optical depth that permits significant light transmission to the underlying water.

Snow Ice (white ice) forms when the weight of a snow cover is sufficient to overcome the buoyancy of the ice supporting it, the ice surface becomes submerged and water flows through cracks in the ice and saturates the snow, which then freezes.
Snow ice is often referred to as white ice because it contains a large number of densely packed air bubbles and small ice crystals that cause strong light scattering and a high albedo.