Pancake Ice on the Androscoggin River in New Hampshire

March 31, 2016

Round river ice 2016 (1)

Photographer: Reuben Rajala
Summary Authors: Reuben Rajala; Jim Foster

Ice disk IMG_0201The photo above shows curious disks of river ice on the Androscoggin River in New Hampshire, near Gorham. For the first time I can recall, dozens of these round plate-like pieces formed on the Androscoggin River just behind my house. Note that I've lived here for 40 years, but even people I talked to who've lived in this area far longer have never observed this phenomenon. This type of ice is called pancake ice. It forms when frazil ice accumulates in flowing water — usually fast flowing water.
I pulled one out (inset photo) to take a closer look. It was about one-half to one inch (1 to 2.5 cm) in thickness, the size of a dinner plate and filled with fine air bubbles. After 3 or 4 days these plates melted as the water warmed.
Photo Details: Top - Camera Maker: Apple; Camera Model: iPod touch; Focal Length: 3.3mm (35mm equivalent: 31mm); Aperture: ƒ/2.4; Exposure Time: 0.0019 s (1/529); ISO equiv: 25. Inset- same except: Exposure Time: 0.0004 s (1/2469).