Ice Circle on Presumpscot River

February 12, 2019

Ice circle 011719 72 (1)

Photographer: John Stetson 
Summary Authors: John Stetson; Jim Foster

February 2019 Viewer's ChoiceShown above is an impressive ice circle or ice disk on the Presumpscot River as viewed from Westbrook, Maine on January 17, 2019. It stretched almost from one bank to the other and was approximately 300 ft (91 m) in diameter. There are several ways such frozen disks may form, but it seems now that when observed on rivers and streams these nearly perfect circular shapes are driven by changes in water temperature. When warmer less dense water just below the surface of a river is cooled by ice that rapidly forms on the water's surface, a vortex may form. If the river has sufficient flow, the ice may begin to spin - the warmer the water the faster the spin. The ice disks will continue to rotate until the surface and subsurface water temperatures are about the same or when the disk becomes stuck on a river bank or some object in the river (a floating log, ice along the shore, etc). Click here to see a video of this ice amazing ice circle.

Photo Details: Camera: NIKON D700; Software: Adobe Photoshop CS4 Macintosh; Exposure Time: 0.010s (1/100); Aperture: ƒ/22.0; ISO equivalent: 200; Focal Length (35mm): 16.