I listened to Tom Rosenbaur’s Orivs Fly Fishing Guide Podcast on winter fishing techniques the other day. During the show I was struck by a phenomenon he mentioned called anchor ice. Having never heard of it before I dug up a little info on it. Apprently its ice that grows straight up from the bottom of the river. Who knew?
Since the basic laws of physics dictate, and we all know from hours of starring at an iced tea glass, ICE FLOATS. So how does it form on the bottom as anchor ice?
Wikipedia has this to say:
Anchor ice will generally form in fast-flowing rivers during periods of extreme cold. Due to the motion of the water, ice cover may not form consistently, and the water will quickly reach its freezing point due to mixing and contact with the atmosphere. Ice platelets generally form very quickly in the water column and on submerged objects once conditions are optimal for anchor ice formation. Anchor ice in rivers tends to be composed of numerous small crystals adhering to each other in small flocculent masses. Anchor ice in rivers can seriously disrupt hydro-electric power plants by significantly reducing flow or stopping turbines completely.
Another form of anchor ice may be observed at the mouths of Arctic rivers where fresh water seeps out of the river bed into the ocean up through the sediment. Anchor ice forms if the seawater is below the freezing point of the river water.