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article imageWarming oceans could shift earth's axis

By Bob Ewing     Aug 26, 2009 in Environment
A recent study claims human-induced warming of the oceans could shift Earth's axis up to 1.5 meters (4.9 feet). This shift could happen by the end of the century.
Discovery News reports the study will be published in the journal Geophysical Research Letters. A team of researchers has found rising sea levels caused by warming oceans also play a significant role in pushing the poles around.
Scientists are aware the earth continually wobbles. As the seasons change, the planet's poles are temporarily pushed askew due to changes in air and ocean circulation.
Until recently, scientists believed it was only the disappearance of glaciers since the last ice age that produced an effect as they pulled the north pole towards Canada.
The team found sea level rise caused by warming oceans is a major factor in pushing the poles around.
When the ocean temperature rises, the water expands> this expansion forces seal levels upwards. It is estimated this effect to raise the global shoreline by about 3 millimeters (0.12 inches) per year over the next century which is a one inch cumulative rise.
As warming gets into the deep ocean, it pushes up the water above it," said Felix Landerer of Jet Propulsion Laboratory in Pasadena, Calif.
"Some of the mass gets transferred up onto shallow continental shelves."
This extra water moving into the shallows is heavy enough to push the planet's rotational axis a tiny bit closer to Alaska.
"It's a completely unexpected result," Richard Gross, also of Jet Propulsion Laboratory, said. He was not involved in the study.
"The conventional thinking has been that... sea level changes won't affect Earth's rotation."
Melting ice sheets also have an effect, though their effect is greater, when the melted ice flows into the oceans and redistributes the weight.
Greenland's melt water causes sea level to rise around 0.2 millimeters (0.01 inches) each year, however, it moves the pole the same amount as warming.
"Greenland melting has about a ten times stronger effect on polar motion," Landerer said. As the ice sheet continues to disintegrate in the future, he added, "the effects on polar motion will be dominated by Greenland."
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