Rippled Ice on the Mackenzie River at Fort Providence, May 1992
Normally we encounter ice that is pretty smooth on the underside in winter, but during spring the underside of the ice may become rippled if there is a source of warm water upstream. This photo was taken near Fort Providence during breakup 1992, at the head of Providence Rapids, where the river typically first opens up. Thus the incoming flow had been heated by the sun and by warm overlying air. We poked at this ice floe from a distance, using a survey rod, and managed to flip it over. We were rewarded to find a very consistent ripple pattern: 18 to 22 cm wavelength and ~8 cm amplitude. The peaks were sharp and the troughs were wide and flat.
(Photos by UofA River Ice Group, 1992)