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Fri 9 Dec, 2005 09:16 am
AP
Earth's Magnetic Pole Drifting Quickly
By ALICIA CHANG, AP Science Writer Thu Dec 8, 7:36 PM ET
SAN FRANCISCO - Earth's north magnetic pole is drifting away from North America and toward Siberia at such a clip that Alaska might lose its spectacular Northern Lights in the next 50 years, scientists said Thursday.
Despite accelerated movement over the past century, the possibility that Earth's modestly fading magnetic field will collapse is remote. But the shift could mean Alaska may no longer see the sky lights known as auroras, which might then be more visible in more southerly areas of Siberia and Europe.
The magnetic poles are part of the magnetic field generated by liquid iron in Earth's core and are different from the geographic poles, the surface points marking the axis of the planet's rotation.
Scientists have long known that magnetic poles migrate and in rare cases, swap places. Exactly why this happens is a mystery.
"This may be part of a normal oscillation and it will eventually migrate back toward Canada," Joseph Stoner, a paleomagnetist at Oregon State University, said Thursday at an American Geophysical Union meeting.
Previous studies have shown that the strength of the Earth's 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 rate of the magnetic pole's movement has increased 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.
The north magnetic pole was first discovered in 1831 and when it was revisited in 1904, explorers found that the pole had moved 31 miles.
For centuries, navigators using compasses had to learn to deal with the difference between magnetic and geographic north. A compass needle points to the north magnetic pole, not the geographic North Pole. For example, a compass reading of north in Oregon is about 17 degrees east of geographic north.
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.
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we are actually developing a series of higher "harmonic" poles as the apparent polar drift is increasing. We have a series of tripoles in the south Pacific and these are gaining strengthg.
We are due for a polar reversal and , new data states that a full reversal period is about 7000 years on average. Then the poles can stay in their reversed position for a hundred or more thousand years.
The poles arenr declining in field strength(no matter what the Creationists say). We have a field intensity now, even though the decline is roughly 1/1500% per year, thats about 3 times greater than it was in the early Pleistocene (asseen from remanent mag studies on paramagnetic sediments and ferromagnetic volcanics.
It will be cause for some concern re: melanomas.
Can you expand on the last part, farmerman? This whole thing sounds alarming, would appreciate your take on it one way or the other.
so what happens where there is a reversal?
husker wrote:so what happens where there is a reversal?
Nothing much other than your compass reads in reverse.
husker wrote:so what happens where there is a reversal?
Heaven and Hell swap places
We need to put the pole in a vault.
A friend studying the pole reversal phenomenon
told me, when it happens anything electric will be useless. I'm not sure I understand why this would happen or if my friend was full of it or not.
dont worry Ceili, we can generate electricity in a number of ways . Even if the shift occurs , wed still be left with about 25% of our mag field and , since there is no evidence from the fossil record that any extinctons coincide with polar shifts , maybe we will make it through ok.
However, there is a school of panicking atmospheric scientists who are predicting that much of our atmosphere gets "stripped away" by solar winds that are allowed to "blow" unfettered across our planet. Now, sediment records DO show that in some polar shifts the total percentages of xygen isotopes and Nitrogen isotopes decreases in the sediment deposition record. Does that mean that OP2 and N2 are being stripped away ? or does it mean that these gases are being taken up ihn respiration?
I dont know and Id like to hear from one of our panicky climatologists or cosmologists.
Farmerman
A show I was watching about the magnetic poles reversing made it sound like the "flip" would be really quick, like one day, boom, north is south.
Like suddenly there would be a tipping point and they would switch
What you said about it taking 7000 years....
Do you mean the the poles would take that long to totally reverse their positions?
In that case, compasses would be increasingly inaccurate. No?
yes, compasses are pretty much invalid for a long time now We adjust declination almost daily for realy accurate surveys. I just got back from a field site in South America and we were resetting well location transects from data that was about 15 years old, wed had to readjust declination almost 1 degree. For accuracy surveys , one degree is over 90 feet per mile. and we will be drilling holes that are 2or 3 miles apart and 1500 ft deep, so we could miss stuff we want to see.
We mostly use satellite data anymore, and visual econ from 3 key stars in both N and S hemispheres.
When it flips, its gonna take a while, because it isnt a switch from on to off, its an actual decrease in field strength and then a reversal over time. The latest research Id seen was that 7000 years is about the average time to flip a pole. Obviously that has a range . We are living in whats known as the "Brunhes Normal magnetogeochron stage" Its named after this guy who discovered the 700000 year range of the magnetic cycle. Since the Cambrian, weve been able to measure about 20+ reversals. NONE of these reversals had any evidence of extinctions though. The reversals always occured well before, or well after any extinction periods. So, Im not gonna worry. Just buy a lot of No 99.
Whew! Guess I'll go back to worrying about the other more mundane, likely causes of our inevitable extinction. :wink:
Interesting farmer thanks.
But if it takes 7000 to re establish a strong field in the other direction, then there must be a considerable period when the earth's magentic field is diminished, and therefore we are exposed to the solar wind? It blows all the time I believe. What happens during that hiatus?
well find out. The theory is that , even at the de minimus level with multuiple poles all over the earth (at the zero point) the earth will still have about 25% of its normal field.
We dont have data , just models. All models suffer from one important drawback, correctness of the prediction is not a measure of the models success, at least until the models are calibrated against real field data.
besides, since weve had 21 other reversals, we havent seen a major depletion of atmospheric gases just perturbations (we think).
you dont sound all that confident that things will be well
Thats not my job Steve. Jever see how calm some of these meteor impact dudes are when they report on the virtual inevitability that we are gonna get nailed by a large hunk of planet that will slip in from left field and will wipe us out. Hell, the guys on the Weather Channel get more excited about sumer thunderstorms.
farmerman wrote:It will be cause for some concern re: melanomas.
Can u plz elaborate this....
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