WeatherQuesting with April Holladay, Article printer-friendly version

Blue ice

Q: Why is some ice blue? Sherie, Albuquerque, New Mexico

An iceberg and blue ice, Gerlache Strait, Antarctica.  Photo courtesy of NOAA.

A: Ice is blue for much the same reason that water is blue--it absorbs a bit more of the red-frequency part of light that shines on it than it does the blue.

Poke a hole in snow or ice and look down it. You'll see blue-green light because the emerging light has bounced around through many snow-particle passages. At each snow collision, the snow absorbs more red than blue. Eventually, the reflected light is noticeably blue. The white light fades to blue as it bops its way out. The deeper the ice hole, the bluer the returning light.

Sometimes icebergs look green instead of blue. Icebergs contain more stuff than ice---suspended sediments, algae, and air bubbles. These particles contribute to the green color.

Further Reading

Color and Light in Nature by David K. Lynch and William Livingston

(Answered Dec. 13, 2002; updated Sep. 28, 2007)

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