LONDON -- Biologists in Scotland were struck by an unusual discovery this week: ice pancakes the size of dinner plates floating on the River Dee.
More common to the Antarctic or Baltic Seas, they need rare conditions to form, and this is the first time they've been found on the UK river. They were spotted by biologist Jamie Urquhart on the Lummels Pool at Birse, which is 29 miles from Aberdeen.
The pancakes were likely formed after foam floating on the water began to freeze at night. As the frozen foam swirled around the eddy, or current of water, they became circular.
"Perhaps each disc grew when smaller pieces of unfrozen foam struck the disc, adhered and then froze in place," the River Dee Trust said in a blog post published Wednesday.
The inner lines of the ice pancakes were likely formed by the fluctuating air temperature between day and night.
"The air temperature was colder at night due to the clear-sky conditions, but warmer in the day, meaning the discs may have grown at night," the trust said. "Then during the day, when the discs softened in the sun, further collisions between the 'pancakes' caused the rims to be pushed up."
The River Dee, designated as an area of special conservation, provides a habitat for freshwater pearl mussel, Atlantic salmon and otter. It stretches 87 miles from the Cairngorm Mountains to Aberdeen, where it meets with the North Sea.