(Original headline: As magnetic pole shifts, Alaska may lose northern lights )
SAN FRANCISCO (AP) - Earth's north magnetic pole is drifting from North America at such a clip that it could end up in Siberia in the next 50 years, scientists said Thursday.
Despite accelerated movement over the past century, the possibility that Earth's fading magnetic field will collapse or that the magnetic poles will flip is remote. But the shift could mean that Alaska may no longer be able to see the high-altitude shimmering displays of colorful lights called the aurora borealis, or northern lights.
Scientists have long known that magnetic poles migrate and in rare cases, swap places. But exactly why this happens is a mystery.
``This may be part of a normal oscillation and it will eventually migrate back toward Canada,'' said Joseph Stoner, a paleomagnetist at Oregon State University.
Results were presented Thursday at an American Geophysical Union meeting.
Previous studies have shown that the strength of the Earth's protective magnetic shield has decreased 10 percent over the past 150 years. During the same period, the north magnetic pole wandered about 685 miles out into the Arctic, according to a new analysis by Stoner.
The magnetic pole's movement has accelerated in the last century, compared to fairly steady movement in the previous four centuries, the Oregon researchers said.
At the present rate, the north magnetic pole could swing out of northern Canada into Siberia. If that happens, Alaska could lose its northern lights, which occur when charged particles streaming away from the sun interact with different gases in Earth's atmosphere.
Earth's magnetic poles are different from its geographic poles, which indicate the rotation axis around which it spins. The invisible magnetic field is formed by liquid, molten iron spinning in the Earth's core.
The north magnetic pole is where a compass points. It was first discovered in 1831 and when it was revisited in 1904, explorers found that the pole had moved 31 miles since it was first found.
Pole reversals are uncommon, happening at intervals of several hundred thousands years. The last time the poles flip-flopped was about 780,000 years ago.
In the study, Stoner examined the sediment record from several Arctic lakes.
Since the sediments record the Earth's magnetic field at the time, scientists used carbon dating to track changes in the magnetic field.
They found that the north magnetic field shifted significantly in the last thousand years. It generally migrated between northern Canada and Siberia, but it sometimes moved in other directions, too.
