What Happens When The North Pole Becomes The South Pole?

A few days ago I wrote a post about the age of the magnetic field that protects us from the solar wind, it proved surprisingly popular, I hadn't realised geodynamism was such the hot topic. Well, here is a little more excitement for the earth sciences crowd.

Now, I don't want you to panic but since the year 1840 our magnetic field has been getting weaker and weaker at quite a fast rate. Fortunately, this won't ultimately lead to its complete demise but it is thought that it could lead to the north and south poles switching places Yup, that can happen. It's actually happened hundreds of times in the past and there is a consensus that it'll happen again soon, in this case soon means 1-10,000 years.

So should we be worried? Probably not. There are two main concerns about what might happen in the event of a pole switch. Firstly, it doesn't happen overnight. It is a gradual process that is accompanied by an overall weakening of the field for several millennia either side of the flip. Patches of the liquid outer core slowly begin to be polarised the opposite way and when enough of these patches exist the overall polarity of the planet will change. But it can be messy; as the field becomes ever weaker we might even end up with more than one north pole for a time. The concern arises because a weakened field removes much of the protection that I detailed in my previous post. It wouldn't be cataclysmic, as I said, this has happened plenty of times in the past; but large coronal mass ejections (CMEs) during this time could certainly punch a hole in the ozone layer which could have ramifications for skin cancer rates.

The second main concern would be for our precious electronics, they would also be more susceptible to CMEs. Much of modern life is highly dependent on satellites and we in the west wouldn't much like it if we lost portions of our main constellations.

What is completely unknown is how animals that rely on geomagnetism would cope. Pigeons, robins, whales, bees, salmon and many more all use the earth's magnetic field to navigate.

This is all relevant because a new article in the open source Nature Communications has shown that the current weakening in our magnetic field is not unprecedented. It is known that there is an area of very pronounced weakness in our magnetic field that stretches from Brazil, across the south atlantic and into southern Africa. Scientists have long assumed that, combined with the overall weakening of the past 160 years, this predicts an imminent flip in the field. This paper, however, shows that there was a significant weakening of the field about 700 years ago over much of southern Africa but it then recovered to normal levels. The decline, then, may not be terminal so no need to rush out and buy shares in sunblock manufacturers just yet.

During a reversal the magnetic field is clearly drunk and should just go home. Image courtesy of NASA