Photographs emerged this week of what have been dubbed ‘ice pancakes’ forming on the surface of the River Dee at Birse.
The formations are rare, and are more commonly seen in the Antarctic, however staff at the River Dee Trust believe they have found an explanation of how they materialise.
Dee Catchment Outreach Office Joanna Dick said: “What we think happened is this: foam floating about on the water started to freeze, probably at night.
“Bits of frozen foam got pushed around in the eddy, and in the ensuing collisions, became roughly circular. Perhaps each disc grew when smaller pieces of unfrozen foam struck the disc, adhered and then froze in place.
“The raised rims are undoubtedly due to the collisions but what about the inner lines?”
Joanna explained: “The air temperature rising being colder at night due to the clear-sky conditions but warmer in the day means the discs may have grown at night, collecting new foam, then during the day, when the discs softened in the sun, softening particularly around the edges, the collisions raised up the rims. The next night, further growth followed by a new rim the next day with a greater size.”
River Dee Trust biologist Jamie Urquhart captured the “ice pancakes” on camera, which led to widespread speculation on social media over what they might be.
Some of the more unusual suggestions ranged from frozen lily pads to giant prawn crackers!
According to expert group ASPeCt (Antarctic Sea Ice Processes & Climate) the so-called ‘pancake ice’consistsof circular pieces of ice of around 30cm–3m in diameter, which may be formed in the Antarctic on a slight swell from grease ice, shuga or slush or as the result of the breaking of ice rind, nilas or, under severe conditions of swell or waves, of grey ice. Eventually the pancakes can freeze together into larger floes or a consolidated ice cover.