Icebergs in the Antarctic area sometimes have stripes, formed by layers of snow that react to different conditions.
Most icebergs are white due to tiny bubbles trapped inside, which scatter the light in every direction.
Blue stripes are formed when a crevice in the ice sheet fills up with meltwater and freezes so quickly that no bubbles form.
Green stripes are created by the freezing of algae-rich sea water
Photographs taken north of Antartica by Norwegian sailor Oyvind Tangen from a research vessel, and published in March 2008.