Some rather apocalyptically minded people – a couple of whom have actually contacted me – have seen a connection between two recent odd occurrences. First came all those birds falling from the sky over the Christmas period. Then, there was this rather odd report of runways in Florida having to be repainted due to ‘the shift in the location of the Earth’s magnetic north pole’. Perhaps fuelled by fuzzy memories of The Core, my worried correspondents – and others around the internet – are musing whether this is a sign of an imminent magnetic field reversal (or ‘pole flip’ as it is often called), with all of the nebulously dire consequences that would ensue.
In fact, neither the bird deaths, nor the runway realignment, are heralds of anything particularly unusual. On the avian mortality front, some digging by the Christian Science Monitor reveals that on average, mainland North America seems one mass wildlife die-off every two days. According to this report from the USGS, there were eight events that involved more than 1000 bird deaths in 2010, and if anything it was a quiet year. Furthermore, although birds do have the ability to sense magnetic fields, it seems unlikely that some disruption of that ability would cause them to fall from the sky. It might make them a little lost and confused, perhaps.
But crucially, there is no sign of any unusual disruption of the Earth’s magnetic field – the reported runway re-alignment is certainly not one. Here’s what the article from the Tampa Bay Online site linked to above says:
Scientists say the magnetic north pole is moving toward Russia and the fallout has reached — of all places — Tampa International Airport…
…The busiest runway will be re-designated 19R/1L on aviation charts. It’s been 18R/36L, indicating its alignment along the 180-degree approach from the north and the 360-degree approach from the south.
To check what is going on, I plugged the co-ordinates of Tampa Airport (around 28°N, 82.5°W) into NOAA’s handy online magnetic field calculator, which allows you not only to calculate the magnetic field direction and strength at any point on the Earth, but also track how it has changed over time. Below is the declination – the deviation of magnetic north from true, geographic north – at Tampa airport for the last 20 years.
January 1991: - 2° 37′
January 1992: - 2° 45′ (-8 minutes)
January 1993: - 2° 54′ (-9 minutes)
January 1994: - 3° 2′ (-8 minutes)
January 1995: - 3°11′ (- 9 minutes)
January 1996: - 3° 18′ (- 7 minutes)
January 1997: - 3° 25′ (- 7 minutes)
January 1998: - 3° 33′ (- 8 minutes)
January 1999: - 3° 40′ (- 7 minutes)
January 2000: - 3° 47′ (- 7 minutes)
January 2001: - 3° 53′ (- 6 minutes)
January 2002: - 3° 59′ (- 6 minutes)
January 2003: - 4° 5′ (- 6 minutes)
January 2004: - 4° 11′ (- 6 minutes)
January 2005: - 4° 17′ (- 6 minutes)
January 2006: - 4° 23′ (- 6 minutes)
January 2007: - 4° 29′ (- 6 minutes)
January 2008: - 4° 35′ (- 6 minutes)
January 2009: - 4° 42′ (- 7 minutes)
January 2010: - 4° 48′ (- 6 minutes)
January 2011: - 4° 54′ (- 6 minutes)
What this shows is that the ‘shift in the location of the pole’ that has necessitated the Tampa runway realignment is not a big, recent jerk – instead, it’s the result of the gradual – and entirely unremarkable – motion of the magnetic pole relative to the geographic pole over the past few decades (what people who study the Earth’s magnetic field call secular variation). In the figure below, I’ve included a British Geological Survey plot of the magnetic pole’s motion from a location in the northern reaches of Canada into the Arctic ocean in the past century. This motion has produced a steadily more negative declination in the vicinity of Tampa Airport over the past couple of decades. A look at Google Maps indicates that the main runways at Tampa have an absolute (geographic) orientation close to due north. Many aircraft (particularly smaller, non-commercial aircraft) still use a compass to direct their course, and pilots need to know what direction the runway is oriented, particularly at night or in bad weather, when visibility is limited. With a negative magnetic declination, you would have to fly at a magnetic bearing a few degrees east of north to parallel the runway.
The numbers on runway numbers are their bearing relative to magnetic north to the nearest 10 degrees, divided by 10 (e.g., 5=50°, 22=220°). For the past few decades the small declination at Tampa has effectively rounded to 0, and the runway numbers reflected this. Now however, the declination is on the verge of being more than -5 degrees*, which rounds to 10; this means that the runway markings must be updated to tell pilots that they should set their landing course to a bearing of 10° rather than 0, or 190° rather than 180 if you’re flying in the opposite direction.
So move along, nothing to see here. For those who are interested in what the real prospects for a future reversal of the Earth’s magnetic field are, I’ve already written an opus on this subject. Basically, the magnetic field will not be reversing any time soon, unless you are talking about ‘soon’ in the sense of ‘in the next few tens of thousands of years at the earliest’. When it does begin to reverse, it will take several thousand years – probably longer than currently recorded human history – to do so. And given that there is absolutely no correlation between extinction events and magnetic field reversals in the geological record – rather fortunate as there’s a reversal every half a million years on average – I don’t think we have much to worry about when it does happen. Except, perhaps, we might need to repaint our runways more often.
Still, I do have my own premonition. Somehow I can’t help thinking that, as we get closer to some arbitrary milestone in the Mayan’s cyclical calendar, I may have to revisit this subject again.
Update 24th January 2010: Apparently, Stanstead airport in the UK, close to where I grew up, is also having to repaint it’s runway markings for the same reason. Given that this has to be a semi-regular occurence in the aviation world, I wonder why such things are getting more play in the media world right now. Are they deliberately trolling people who are worried about 2012?
*given that the Tampa runways appear to run a little east of true north, their magnetic bearing may already be more than 5°. Also, the numbers above are from a global field model, so are probably not completely accurate at such a local scale. I’d suspect that Tampa airport has performed it’s own direct measurements before deciding to change their markings.