Rode up to Mackinaw yesterday and checked out the blue ice. Huge chunks and most phenomenal. The ice, however, is not actually turning blue. The color is a result of the way sunlight is bouncing off this particular ice.
Sometimes, weather conditions — such as a lack of high winds — allow water to freeze slowly and evenly, resulting in ice composed of large crystals (unlike snow, which is formed quickly and made up of small crystals).
When light hits these big ice crystals, it can travel deep into the structures (compare this to snow, wherein light hits a sharp edge and reflects off of it right away, resulting in blinding white). When the light travels deeper into slowly formed ice, some of the red wavelengths of sunlight — which is the longest wavelength of visible light — get absorbed into the ice structure.
The blue, which is the shortest wavelength of visible light, bounces back out, meet our eyes, and results in a deep aqua color.
See more in her Winter gallery on Flickr!