Blue ice

The question I get asked most during a trip is most likely the one about why icebergs are blue. Most icebergs are white, but sometimes, like in these pictures, they are blue. Strangely enough, people never ask why the water is blue or the sky.

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Blue glacier ice – 70mm, 1/640s, f/8.0, ISO400

Light consists of different colours, caused by different wavelengths. In clear ice, blue light is absorbed the least and thus travels the furthest in ice, creating the blue colour in ice. However, glaciers are formed by falling snow, which is slowly turned into ice. As there is a lot of air bubbles in the snow, glacier ice usually has a lot of air trapped inside. Light rays will reflect off these bubbles before the other wavelengths are absorbed. Because of this, ice with a lot of bubbles will look white. In ice that has had a lot of pressure, these air bubbles are pressed out or are very small. Because of this, the light can travel a lot deeper, resulting in the blue colour.

 

Arjen Drost

Arjen is a Polar ecologist, nature photographer and full time expedition guide on expedition cruise ships in both Polar regions. With his pictures and stories he likes to show the beauty of these very fragile and threatened places.

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