Anchor Ice – What’s it really look like and how does it form?
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This section with all of its text, images and videos was created by
Dr. Edward Kempema at the University of Wyoming.
http://faculty.gg.uwyo.edu/kempema/ |
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Frazil from the nearshore bottom of Lake Michigan. It’s about 40 cm in diameter (16”)!
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Video shows frazil that formed at -4°C (25°F). Why does the water actually warm up? These crystals are growing in real-time.
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Not all ice forms on the water surface. In streams, the turbulent flow can allow the water
column to supercool to temperatures below the freezing point, allowing ice to grow in the
water column. The first ice to appear is frazil (small disks or spicules of ice suspended in
the water column). When turbulence transports frazil to the river bed, the frazil may stick
to the bed, forming anchor ice.
Frazil and anchor ice are most likely to form on a cold, clear night when the wind is
strong, the humidity of the air is low, and the river is at minimum flow, especially if
such a night follows a cold, windy, cloudy day.
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Dr. Ed Kempema’s Underwater Videos
Cobble
Transport
Click
here to visit his website and learn much
more about ice formation in streams and lakes
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UNDERWATER ICE FORMATION
This clip shows mm- to cm-sized frazil crystals suspended
in the water column of an artificial stream channel with flowing water. |
ANCHOR ICE FORMATION
When frazil sticks to the bed it becomes anchor ice. Individual
anchor ice crystals can grow to be several cm in size (more than an inch). |
ANCHOR ICE DISTRIBUTION
More globs of the stuff. |
ANCHOR ICE BRIDGING
More globs of the stuff. As it builds up its buoyancy
eventually causes it to float to the surface. But it has to overcome
the weight of gravel and even cobbles. |
ANCHOR ICE RAFTING
Once anchor ice lifts off the bed it drifts away as
rafts carrying sediment, gravel and even cobbles downstream. |
COBBLE RAFTING
Watch out Titanic This clip shows a 6 pound rock
being floated downstream and then captured by a giant hand. |
ANCHOR ICE EXPERIMENTS
Dr. Ed paints some rocks to measure just how far
material can be transported by this mechanism. |
Many thanks to Dr. Ed Kempema from the U. of Wyoming Geology & Geophysics
Dept. for allowing us to use his materials. His hard work has helped
us to see and understand a phenomenon that occurs in our streams every
year and which can be very important to the ecology of the fish and
other aquatic organisms.
We encourage you to visit his
website to find out about the technical details and scientific importance of his work. |
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