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Antarctic Under Pressure
Fri Oct 31, 2003
Listen in RealAudio 
Folks overwintering at the South Pole have to put up with some of the coldest weather on the
planet--but one of the toughest things they deal with is pressure. Air pressure. Hi, I'm Bryan
Yeaton for the Weather Notebook.
Because the polar plateau averages about 9,300 feet, you might expect only a few people there
would be affected by Acute Mountain Sickness, or AMS. However, the air down on The Ice is
actually similar to an 11,000-foot peak in say, Colorado, which leads to the headaches,
light-headedness, and shortness of breath of AMS.
Like the Arctic, the South Pole region naturally experiences relatively low surface
atmospheric pressures. Even along the coast, pressure averages around 990 millibars compared
to 1013 millibars over most of the planet.
Pressure also decreases with altitude. So at 9,300 feet, oxygen molecules spread out, making
the air feel even thinner.
Additionally, altitude-induced pressure changes are dependent on temperature. Because
Antarctica is always cold--an average of minus 4 degrees F --the South Pole air pressure is
much lower than a similar elevation in the middle latitudes.
All these ingredients can give the South Pole about 35 percent lower oxygen density than at
sea level. Daily downturns in air pressures can make it seem as if you are climbing higher and
higher up a mountain--while never leaving your tent. And during the polar winter, you can lop
off up to another 25 millibars than you'd have in the summer.
Fortunately, humans are adaptable. With a few days of rest and hydration, a headache and
fatigue may be the worst you experience. But every now-and-then, don't be surprised to hear
someone say, "I have a headache --what's the pressure?"
Thanks today to writer Patricia Barnes-Svarney. The Weather Notebook is funded by Subaru of
America, and The National Science Foundation.
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