The magnetic north pole is moving...

[johnalison]

Don't worry. There are TWO magnetic North Poles! There is the Dip Pole, which is where the Earth's magnetic field lines are vertical and there's the Geomagnetic Pole, which is the pole of the average magnetic field of the Earth. The latter is what compasses point to. The Dip Pole (or North Magnetic Pole) is the one that's moving; the North Geomagnetic Pole (to which compasses point) is moving much slower, and the data on charts is still perfectly valid.

It should be valid for the remainder of my cruising career but only this morning there is an item in my paper about the weakening magnetic field, something like 25% less than a century or two ago. Apparently the South Atlantic Anomaly is a major problem, which I was not aware of until I heard about it on YouTube recently. This is set to worsen and will be significant not far into the future, with major implications for satellites.

If the dip pole is moving, I imagine that this might or might not be a sign of pole reversal, but in any case, there should be interesting times, as the Chinese say.

 

[johnalison]

I was always taught and continued to teach that navigational fixes were always historical. A DR or Ep is really what you need. Even GPS is second behind. ..........Not that I like second behinds

I have COG, plus SOG and distance and bearing to waypoint, displayed near the compass. Steering is easiest by compass, keeping an eye on the others, but in practice, steering is often a combined response to the compass, wind-sense, wave direction, sail behaviour, and even the direction of the sun. It is hard to steer well by just staring at a compass, and a more sensitive approach is more successful.

 

[NickCharman]

Don't worry. There are TWO magnetic North Poles! There is the Dip Pole, which is where the Earth's magnetic field lines are vertical and there's the Geomagnetic Pole, which is the pole of the average magnetic field of the Earth. The latter is what compasses point to (to a first approximation; it gets more complicated!). The Dip Pole (or North Magnetic Pole) is the one that's moving; the North Geomagnetic Pole (to which compasses point) is moving much slower, and the data on charts is still perfectly valid.

Thanks - a good reassurance!

 

[AntarcticPilot]

It should be valid for the remainder of my cruising career but only this morning there is an item in my paper about the weakening magnetic field, something like 25% less than a century or two ago. Apparently the South Atlantic Anomaly is a major problem, which I was not aware of until I heard about it on YouTube recently. This is set to worsen and will be significant not far into the future, with major implications for satellites.

If the dip pole is moving, I imagine that this might or might not be a sign of pole reversal, but in any case, there should be interesting times, as the Chinese say.

There has been some recent work on this that suggests it's to do with the relative position of two sources of magnetic field in the outer part of the Earth's core; and that the trend towards Siberia is weakening and may well turn back. At present, there's no real evidence of a field reversal, though as you note, these are frequent on a geological scale and if anything we are overdue for one given the average spacing. The South Atlantic Anomaly has been there as long as we've been launching satellites (it was discovered in the 60s) and although it is and always has been something satellite operators have had to take into account, there's no real change.

 

[crewman]

Anybody know what actually happens to the Poles during a reversal? Does the N Pole move south at some point crossing the equator or does the magnetic field fade away and return in the opposite direction?

 

[AntarcticPilot]

Anybody know what actually happens to the Poles during a reversal? Does the N Pole move south at some point crossing the equator or does the magnetic field fade away and return in the opposite direction?

Quick answer is that we don't know. Longer answer is that PROBABLY the field strength drops to a low value while the pole migrates. We know that the magnetic field doesn't entirely disappear; if it did, there would be serious effects on life on Earth! Timescales are in the hundreds of years. There have been modelling studies. But it will happen slowly over a period of the same order of magnitude as a human lifetime.

 

[RichardS]

I'm amazed how much attention this old thread has suddenly attracted.

What happened to Kelly's Eye anyway? It's seems to be ages since we heard from him.

Richard

 

[johnalison]

Quick answer is that we don't know. Longer answer is that PROBABLY the field strength drops to a low value while the pole migrates. We know that the magnetic field doesn't entirely disappear; if it did, there would be serious effects on life on Earth! Timescales are in the hundreds of years. There have been modelling studies. But it will happen slowly over a period of the same order of magnitude as a human lifetime.

I think I read somewhere that there could even be more than one north/south pole at times, depending on what the liquid part does under our feet. I'm rather sorry to be missing it.

 

[LittleSister]

Don't worry. . . .
the North Geomagnetic Pole (to which compasses point) is moving much slower, and the data on charts is still perfectly valid.

Damn! So I can't use the change as an excuse for any navigational errors?

 

[Sandro]

I am asking (supposing the answer is known to scientists) which way the magnetic field flip has happened/will happen.
I imagine two possible ways: to overcome my poor English language I'll explain myself with an exemple of two ways of wind shifting from N to S:
1.- force 4 N, 3 N, 2 N 1 N, calm, 1 South, 2 S, 3 S, 4 S.
2. - force 4 N, 4 NE, 4 E, 4 SE, 4 S.
The magnetic field could reverse in similar two ways.

Antarctic Pilot, why does compass point to Geomagnetic pole instead of to Dip pole?
Reading the article referred to in post #58 did not make clear to me what Geomagnetic pole is.
Same as lpdsn, "I'm struggling to visualise the field lines" at a distance from Dip pole other than vertically pointing more and more down while approaching it but horizontally always pointing to it.

Sandro

 

[AntarcticPilot]

I am asking (supposing the answer is known to scientists) which way the magnetic field flip has happened/will happen.
I imagine two possible ways: to overcome my poor English language I'll explain myself with an exemple of two ways of wind shifting from N to S:
1.- force 4 N, 3 N, 2 N 1 N, calm, 1 South, 2 S, 3 S, 4 S.
2. - force 4 N, 4 NE, 4 E, 4 SE, 4 S.
The magnetic field could reverse in similar two ways.

Antarctic Pilot, why does compass point to Geomagnetic pole instead of to Dip pole?
Reading the article referred to in post #58 did not make clear to me what Geomagnetic pole is.
Same as lpdsn, "I'm struggling to visualise the field lines" at a distance from Dip pole other than vertically pointing more and more down while approaching it but horizontally always pointing to it.

Sandro

Basically, the field is not a simple dipole, like the field of a bar magnet. A compass needle points along the lines of force where it is, and on a global scale that will approximate the average dipole field, so on the whole, it points towards the pole of the mean dipole field, the Geomagnetic Pole. But near the pole the non-dipole components start to dominate, and so the field lines aren't vertical at the pole of the dipole field, but are displaced from it.

I'm not really an expert in geomagnetism, and I'm sure some of my former colleagues would pick holes in my explanation! But it's close enough for our purposes.

 

[Sandro]

Thank you. So, if I understand, where my compass is, a field line is alined with Geomagnetic Pole, then, going North, it bends down and slowly say right, before sinking vertically in the ground (sorry, sea) in the Dip Pole.
The real thing is always much more complex than the basic models we make in our minds, as though seeing the earth as a big regular bar magnet.

 

[PeterWright]

Not that any of us will be there, when the next flip happens, if as mostly believed, it goes through a vary low field strength period, we will have far more to worry about than our compasses not working.

The Earth's magnetic field is just one of the happy conjunction of natural effects which makes the Earth habitable, without it, we would be heavily bombarded with cosmic rays, which the magnetic field currently deflect away from us. Just flying for a few hours in the upper atmosphere irradiated you more than staying at ground level and up there you still get a good deal of protection from the Earth's field. I spent the majority of my life working in nuclear power and accrued more radiation dose from flying than from occupational exposure.

Peter.

 

[LittleSister]

It seems that while the magnetic poles are flipping navigation may be the least of our worries!

End of Neanderthals linked to flip of Earth's magnetic poles, study suggests

 

[AntarcticPilot]

It seems that while the magnetic poles are flipping navigation may be the least of our worries!

End of Neanderthals linked to flip of Earth's magnetic poles, study suggests

I know Richard Horne, and his response would, I'm sure, have been much more nuanced than the quote in the article. But basically, it's someone spotting a correlation and forgetting that correlation doesn't imply causation. You could only say it was true if many other species had also suffered similar extinction events - and that doesn't appear to be the case. On a geological timescale, magnetic reversals are common - they happen at intervals of less than a million years; a barely discernible length of time geologically. If they had major effects on populations, we'd know all about it. It is possible that it might push a population right on the edge over (that could be the case for Neanderthals), but a robust population would be fine.

 

[afterpegassus]

.... in which case, they can just move the boat to wherever the north pole goes.

ie go with the floe..

 

[doug748]

ie go with the floe..

Snow need to be flippant.

 

[LittleSister]

An entertaining and informative update on the potential for the Earth's magnetic field to flip and/or dissipate in the near future.

 

[LittleSister]

Never mind poles flipping, what if we suddenly (relatively speaking) had no magnetic field? (see vid below)

I know Richard Horne, and his response would, I'm sure, have been much more nuanced than the quote in the article. But basically, it's someone spotting a correlation and forgetting that correlation doesn't imply causation. You could only say it was true if many other species had also suffered similar extinction events - and that doesn't appear to be the case. On a geological timescale, magnetic reversals are common - they happen at intervals of less than a million years; a barely discernible length of time geologically. If they had major effects on populations, we'd know all about it. It is possible that it might push a population right on the edge over (that could be the case for Neanderthals), but a robust population would be fine.

As you say, correlation doesn't imply causation. On the other hand there's a particularly intriguing major correlation between populations and magnetic field changes, almost as an aside to the thrust of this article and the research it highlights.