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Polar Ice Caps
Name: Jordan
Status: Student
Age: 6
Location: N/A
Country: N/A
Date: N/A
Question:
Why does the earth has ice at the top and bottom all the
time, but not over the rest of the earth? - Jordan
Replies:
Jordan,
Areas where it is cold most of the time, like the poles, the tops of high
mountains, and places like Greenland get snowfall most of the year and
have temperatures below freezing most of the year. The snow compresses
over time and becomes ice at the higher elevations. It is just plain very
cold
at the poles most of the year, so even sea water stays frozen at the North
pole, and the snow and
ice do not melt on Antarctica. The North pole has been a bit warmer the
past 15 years, so the ice
has thinned there to about half of what it was 25 years ago.
David R. Cook
Atmospheric Section
Environmental Research Division
Argonne National Laboratory
As the earth circles the sun, the line connecting the centers of each
reaches only the tropic of cancer in the northern hemisphere and the tropic
of Capricorn in the southern hemisphere. If you can find a globe, you will
see these latitude lines marked.
Then if you take a flashlight and stand about 10 or 20 feet away from the
globe and direct the flashlight's beam at either of these latitude lines,
you will see that neither the North or South pole gets much sunlight in
either winter [for us] when the sun is at the tropic of Capricorn, or at the
tropic of cancer in summer [for us]. Things are just reversed in the
southern hemisphere. Because there is such sunlight reaching the poles and
that sunlight is at a low angle relative to "straight up", the zenith,
neither pole is able to receive enough solar energy to warm up very much.
Vince Calder
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Update: June 2012
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