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.
Click here for more lake ice terms.
Above: MST Pond ice cover illustrating black ice (right) and white ice (left). MST Pond is on the Poker Flat Research Range ~50 km northeast of Fairbanks.
Left: The processes leading to congelation ice (1) and snow ice (2-4).
Vertical thin section showing granular snow ice (top) and columnar congelation ice (bottom). Vertical thin section showing 15-31 cm of ice core. Horizontal thin sections at 15 cm (far left) and 31 cm (near left).
Thin Sections
Thin sections are made by cutting ice cores vertically or horizontally into very thin layers. These layers allow light to pass through them. When thin sections are placed between cross-polarizing filters on a light table the crystallography of the ice is revealed
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