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melt, sea level will increase dramatically.
The Antarctic hosts 29.400.000 km3 of glacial ice, while the Arctic hosts only 3.100.000 km3 of glacial ice,
85% of which is stored in Greenland s Ice Sheet.
In and around the Arctic Ocean there are polar bears, but no penguins. The Antarctic coasts teem with
penguins, but there are no polar bears. In the Antarctic dogs are banned, while dogs abound in the Arctic,
at least 30.000 sled dogs in Greenland alone.
In the Arctic high summer occurs in June August, while during this period the Antarctic lies dormant and
deep frozen immersed in aurora australis, moonlight and star shine.
However, both the Arctic and the Antarctic have a pole , that is the point where the (extension of) Earth s
rotation axis intersects the Earth s surface. The word pole originates from the Greek polos which means
the midpoint of ration .
See the light
We all look up at the sky many times a day. Have you ever wondered what makes the colours of the sky?
The light from the sun includes all colours of the rainbow, i.e. a colour palette with blue continuing through
green to yellow and red. 99% of the atmosphere are oxygen and nitrogen molecules, minute entities of
approx. 30 nm (nanometres). When direct sunlight hits these molecules, they absorb most of the shortDanish
Polar Center
IPY Service Manual for Kangerlussuaq 2008
version 1 June 2008
Compiled and written by Henning Thing (het@fi.dk)
Danish Polar Center Danish Agency for Science, Technology and Innovation
page 59 of 60
waved (420-490 nm) blue colours and therefore passively radiate blue-coloured light indirectly to their surroundings.
Therefore, a daytime sky above the clouds is seen by human eyes as blue, especially around
noon when the sunlight is highest over the horizon and is predominant because it has the shortest distance
to us through the atmosphere. [Water surfaces, e.g. lakes and ocean, appear blue during daytime because
they reflect the colour of the sky].
The sun itself appears to be a yellowish disc on the sky. This again is due to the atmosphere s oxygen and
nitrogen that absorb, and therefore remove, the blue colours from the direct sunlight. The remaining colours
of the incoming light are a mixture of yellow, orange and red which our human eyes perceive as a yellowish
colour. If one could stand on the Moon, which has no atmosphere, and look at the sun it would appear
white and the sky would be black. Remember that the colour white is a mixture of all colours.
Compared to the air molecules, the droplets of the clouds are very large (approx. 1000 nm). When sunlight
hits the droplets it is deflected equally in all directions. This results in white light and, therefore, the clouds
their white colour.
At sunset and sunrise the sky is often glowing in reddish colours. The sun is at a low angle and light, therefore,
has to travel a longer distance through the atmosphere than at e.g. noon. The shortwaved violet and
blue colours have been absorbed and diffused by the oxygen and nitrogen molecules of the atmosphere
long before the sunlight reaches our eyes. Therefore, here on the surface of the Earth we see the low sun in
the remaining and longwaved light: yellow-orange-red. If unusually many small particles are suspended in
the atmosphere, e.g. in connection with volcanic eruptions, forest fires and city smog, the diffusion of violetblue
colours is greatly augmented and the sunrises and sunsets will turn into deep red events.
The colours of the sky at night are due to aurora borealis, the northern light. Its spectre is limited when
compared to that of the sunlight, but again oxygen and nitrogen are important elements. The characteristic
reddish and yellow-greenish colours of the northern light emanate from oxygen atoms hit by the energy-rich
electrons of the solar wind at an altitude of 100-400 km. If these electrons collide with nitrogen ions (N2
+)
the bluish colours of the northern light appear. A mixture of the colours mentioned above is perceived by the
human eye as a whitish northern light.
Winter sun
During the dark northern winters there are many good reasons to look at the bright side of Life. The winter
sky may provide you with beautiful incidents if you are outdoors. When thin clouds at 5-10 km above also
known as cirrostratus veil the bleak winter sun, they create an exceptional light marvel in the sky: Halos
and sundogs.
This cloud type contains a multitude of flat ice crystals 0.05 - 1 mm across. They are hexagonal and of very
pure frozen water. While they very slowly falling (because of the law of gravity) towards the Earth holding
their flat broadside horizontally they all act as regular prisms refracting the sunlight in a similar manner. Although
　
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