Icebergs only appear to be white when they are covered with a layer of snow. They are actually blue as photographer Alex Cornell has caputred here as part of a hauntingly beautiful series of photographs he took in Antarctica.
Cornell says that it had snowed in the area recently, but this one had flipped over, exposing its real self.
The ice is blue for the same reason the sea is – blue light is scattered by tiny particles, not unlike the way it is in the atmosphere to make the sky appear blue (which we explained in the first of our Why is it so? series) .
In the oceans – and icebergs – there is also a lot of absorption of the red end of the spectrum. NASA goes into more detail.
The red, yellow, and green wavelengths of sunlight are absorbed by water molecules in the ocean. When sunlight hits the ocean, some of the light is reflected back directly but most of it penetrates the ocean surface and interacts with the water molecules that it encounters. The red, orange, yellow, and green wavelengths of light are absorbed so that the remaining light we see is composed of the shorter wavelength blues and violets.
But the sea can also be shades of green, to blue-green. For that we have phytoplankton to thank.
The most important light-absorbing substance in the oceans is chlorophyll, which phytoplankton use to produce carbon by photosynthesis. Due to this green pigment – chlorophyll – phytoplankton preferentially absorb the red and blue portions of the light spectrum (for photosynthesis) and reflect green light.
The study of ocean colour helps scientists gain a better understanding of phytoplankton and their impact on the Earth system.
Hat tip to Mashable for the images.
Bill Condie is a science journalist based in Adelaide, Australia.
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