Winter Phenomena |
As winter transforms lakes and streams, we may notice things that were obscured by the displays of spring and summer. Ice and snow take on strange forms, colors, and textures. Colder temperatures change the dynamics of aquatic ecosystems, but the world beneath the ice is not as dormant as it seems. |
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| Snow fleas |
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Black specks on snow, especially around the base of tree trunks, are insects called snow fleas. Look closely and you will see them crawling and jumping around. Snow fleas are not really fleas but members of a group of insects called springtails. They are most apparent when the snow pack starts to thaw in late winter, when they congregate in large numbers on sunny days to feed on pollen, microscopic algae, and fungi on the surface of the snow. |
Algae beneath the ice |
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Clumps of algae beneath ice in spring. |
Another phenomenon of early spring is the appearance of algae beneath ice and snow. As the sun gets stronger and the snowpack begins to thaw, pulses of nutrients fuel growth of algae in shallow flooded areas. |
All about ice...
Water is lighter in its solid state than its liquid state so ice floats. Most compounds are heavier as a solid; were it not for this unique property of water, lakes would freeze solid from the bottom up. Instead, ice forms on the surface, sealing in the life below, at times protecting it.
Black ice is clear and free of gas bubbles, and appears dark over deep water. White ice forms when water saturates lower snow layers, and trapped air bubbles reflect and scatter light. |
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| "Frazzle" or frazil ice forms as needle-like crystals or thin, flat circles in the water when the surface is "supercooled" to just below freezing. Frazil ice is the beginning of slush, pancake, anchor, and other ice forms. River currents move the ice crystals, causing them to form circles or plates. |
Slush forms at the foot of a dam on Branch Brook. |
"Pancake ice" formed from slush on the Saco River.
D. Townsend photo
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S. Nelson photo |
In tidal rivers, the fluctuating water levels tend to thicken ice, create stress cracks, and piles of ice chunks and globes. This picture shows spheres of ice on the Kenduskeag River in downtown Bangor. The tidal action pushes the river up and down against the sides of concrete canals, and the ice balls pile up on the edges. |
| Berms may form along shore where ice is in contact with the land. As water levels change in winter and spring the ice pushes up the land surface. Shelves of ice may hang suspended above the water surface after the water level drops. Fallen trees and bank erosion may occur as this "anchor ice" floats away. |
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The Melt Ice first weakens in shallow areas; often a band of open water develops along shorelines before the ice weakens over the deeper, middle part of the lake. Ice also opens up around rocks and plant stems, because they absorb the sun's heat and warm the surrounding water. |
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Back to top of page Some of the information on this page is from the notes of Warren Balgooyen. Links Maine River Flow Advisory Commission - river ice, flow conditions, ice jams Maine Snow Survey Ice jams and River Ice Glossary - from the U.S. Army Corps of Engineers All about snowflakes National Snow Analyses - National Weather Service |
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