This nifty animated GIF shows movement of the magnetic north pole, the bigger green dot, from 1965 to present. You’ll notice two things immediately: (1) it has moved a long ways over that interval, and (2) the rate of movement has accelerated in the most recent time. A recent survey by a Canadian–French international collaboration determined that the Pole is moving approximately north-northwest at 55 km per year. It’s moved past the true north pole and, given the realities of mapping on an oblate sphere, is or shortly will be headed south.
Why? In a kind phrase, the process is “not well understood.” As far as WC can tell, there are about as many theories as there are geomagnetologists; more actually, since some of the geomagnetologists went to Harvard.
At the same time, the overall strength of the earth’s magnetic field is weakening. Some estimates put the decline at as much as 10-15%.1
There’s been a lot of speculation that these are the initial phases of a switch in the earth’s magnetic field, when the magnetic north and south poles exchange places. Certainly that’s happened a lot in geologic history, most recently about 770,000 years ago. This swapping – technically, a change in polarity – is recorded in the ocean rifts. As lava cools, the iron crystals in it align themselves to magnetic north-south. Think of it as a kind of tape recording of a history of those changes of polarity.
And it’s certainly true that the earth’s magnetic field is important. It helps protect life from some high energy particles like cosmic rays, and is embedded in technologies like GPS. If the magnetic field were to collapse entirely, or even substantially weaken, there would be consequences, although perhaps not as dire as some speculate. Certainly we’d all have to get new magnetic compasses.
But there are two things to keep in mind as the magnetic north pole sprints towards Siberia. First, the magnetic polarity reversal is a long, long process, at least 10,000 years and maybe 100,000 years. This isn’t going to happen tomorrow, or overnight, if if happens at all. Second, the combined slight weakening of the magnetic field and accelerated movement of the magnetic poles has happened many times in the past without ever developing into a reversal. In fact, they’ve been given a name: geomagnetic excursions.
Recent studies have found two pretty similar events: the Lascamp, which occurred around 41,000 years ago, and the Mono Lake, which occurred around 34,000 years ago. Researchers found that while the magnetic field at those times looked nothing like it does today, the same combination of field weakening and rapid magnetic pole movement were present, without a magnetic polarity change ever occurring. That suggests current developments aren’t necessarily warning signs of any impending reversal.
The processes that generate the earth’s magnetic field are immensely complex. While they are dominated by the molten iron of the earth’s outer core, the ocean currents, the ionosphere and other, less well understood forces also contribute. How those different sources interplay is still pretty obscure. In the meantime, if you are using a magnetic compass, adjust the declination accordingly. Otherwise, there are far more urgent, far more threatening and far more impending threats to worry about.
- Like everything else involving these issues, it’s complicated. The current decline seems to be mostly associated with the South Atlantic Anomaly. That’s an area stretching across the Atlantic Ocean from Chile to Zimbabwe. The magnetic field is substantially weaker there than elsewhere in the world. Ever since this region was discovered in 1958, it’s been growing, as part of an overall weakening of the entire magnetic field over the last few centuries. ↩