Ice Circles in a Pond

March 04, 2012

PondCircles190002

Photographer
: Ingeborg Evans
Summary Author: Ingeborg Evans; Jim Foster

The photo above shows curious ice circles on a pond near my home in Hamilton, Ontario. This is the first time I've noticed this phenomenon in the 27 years I've lived here. These circles are approximately 6 ft (2 m) in diameter and were observed to slowly spin even though there's little current in this pond. While frazil ice can form circles in relatively fast flowing water, pond water is typically quite still. Perhaps convection from beneath the surface caused circular eddies to form and freeze when heat loss cooled the water temperature to 32 F (0 C). Note that the ice appears thinner and clearer at the center of the circles. It’s also possible that water was extruded upward through a small opening at the circle's center, spreading out before freezing. Additionally, it’s been suggested that stones thrown onto the water surface just when the ice was beginning to freeze would result in the sort of circular structures seen above. Photo taken on December 12, 2011.

Photo details: Camera Maker: OLYMPUS CORPORATION; Camera Model: u30D,S410D,u410D; Focal Length: 7.7mm; Aperture: f/3.6; Exposure Time: 0.0063 s (1/160); ISO equiv: 64; Exposure Bias: none; Metering Mode: Matrix; Exposure: program (Auto); White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB; .Software: Version 1.1.