A few weeks ago, commenter Phil Chapman left this comment in a remote corner of the blog:

It is not quite correct that changes in the geomagnetic field have been unimportant in the time frame covered by your post on solar influence on glaciation. It is true that the last major pole reversal was 780 kya, but lesser geomagnetic excursions are more frequent. The last one, known as the Laschamp event, was only 41 kya. It involved a full reversal, but the whole thing lasted only 440 years. During the change, the field dropped to 5% of its former value, and the cosmic ray flux more than doubled. The scary thing is that we now seem to be in the early stages of a similar event. The N magnetic di pole has left the Canadian Arctic; it is now at 86 N and barreling towards Siberia at 60 km/yr. This is as fast as the maximum speed during the Laschamp event. If it continued, compasses would point at some point on the equator only 180 years from now — but it will probably break up long before then. The very recent data from the ESA Swarm satellites indicate that the field is becoming disorganized and decreasing in intensity by 5%/decade. It seems quite likely that we will lose the protection of the geomagnetic field within decades to perhaps a century, exposing satellites, communication systems and terrestrial power grids to serious damage, and requiring much heavier shielding for astronauts in Earth orbit (and perhaps for people at high latitudes, such as Scotland). Moreover, if the field weakens substantially while we are still in the coming Grand Solar Minimum, the climate may become much colder than the Little Ice Age. This prospect demands immediate serious attention, including objective studies of the connection between GCRs and climate, close observations of the evolving solar and geophysical phenomena, and preparation of contingency plans to counter the effects on agriculture, public health, the economy and living conditions. Phil Chapman (Sc.D., physics, MIT, long ago)

Scottsdale, AZ

This was in response to my post on Solar influence on glaciation in Greenland where I examined the co-variance of the cosmogenic isotope 10Be with Dansgaard–Oeschger events (D-O events). It is not every day that a retired NASA astronaut calls by to share his knowledge and I decided to dig a little deeper into what he had to say.

Paleomagnetism

When igneous rocks (those that crystalise from molten magma) crystalise and cool they record both the orientation and declination of Earth’s magnetic field. Paleomagnetic data have been fundamental to developing the theory of plate tectonics and for working out the history of continent movements and the opening and closing of oceans on Earth.

One of the most important data sets comes from the ocean basins which shows that Earth’s magentic field has reversed on a semi-regular basis (Figure 1). During a reversal the Earth’s di-pole magnetic field flips so that a compass would point to the opposite pole. What Phil Chapman has explained is that during a reversal the field becomes disorganised and the field strength falls to a fraction of that observed in recent times. Furthermore, failed attempts at reversal may be more common than successful full reversals.

Figure 1 Igneous rock (basalt) is being continuously injected along the Earth’s mid-ocean ridges. As the basalt cools and is driven away from the ridge by subsequent injections of basalt it cools and records the orientation of Earth’s magnetic field. The magnetics of the ocean floor exhibit a striped pattern indicating that magnetic reversals have occurred regularly throughout the recent history of the Earth. The cartoon comes from Newgeology that offers a more complete explanation. Reversals occur on a time scale of approximately 200,000 years.

The Importance of Earth’s Magnetic Field

The Earth lies within the magnetic field of the Sun and this offers some protection from galactic cosmic rays that are extremely high energy particles that probably originate in supernovae somewhere in our galaxy. One theory to explain recent climate change on Earth is that cosmic ray bombardment is partly responsible for nucleation of clouds and that variations in the cosmic ray flux, caused by fluctuations in the Sun’s magnetic field, causes fluctuations in global cloud cover and hence global temperatures.

Cosmic rays are also responsible for the creation of the short lived radioactive cosmogenic isotopes 10Be and 14C. Studying the record of 10Be in ice cores and 14C in organic matter therefore provides a means of comparing cosmic ray flux with climatic reconstructions. This was the objective of my post comparing 10Be and temperature variance in the GISP 2 ice core (Figure 2).

Figure 2 Comparison of variance in 10Be (cosmic ray flux) and temperature (D-O events) in GISP2. Note that the 10Be scale is reversed and that temperature is therefore negatively correlated with cosmic ray flux. The co-variance is imperfect but is quite marked in the interval before 25,000 years ago. Note how 10Be is going off scale 40,000 years ago! The GISP 2 core does in fact extend to 50,000 years and I am somewhat bothered by the fact that the 10Be record is curtailed at 40,000 years, right on what is perhaps the most significant event in the record.

It is not only the Sun’s magnetic field that protects Earth from cosmic rays. The Earth has its own magnetic field that originates in the outer molten core and this performs two vital functions. It provides further protection from galactic cosmic rays AND it provides vital protection from the Solar Wind – the stream of high energy particles that is continuously emanating from the Sun (Figure 3).

Figure 3 Cartoon showing how Earth’s magnetic field deflects the solar wind that is drawn in along magnetic field surfaces at the poles. During a magnetic reversal this magnetic field is greatly reduced exposing Earth to the full glare of the solar wind and increased exposure to cosmic rays. Image source. Times of strong solar wind (high solar geomagnetic activity) gives rise to the aurora borealis (Figure 4).

Figure 4 The aurora borealis is caused by high energy particles from the Sun being funnelled into Earth’s atmosphere by the magnetic field at the poles. Image source.

Without our magnetic field, the solar wind would strip away the atmosphere and hydrosphere leaving Earth a barren wasteland like Mars. It is not possible to overstate how important Earth’s magnetic field is for our survival. So what would happen should it fail?

The Laschamp Event

The Laschamp Event is named after the Laschamp lavas near Claremont Ferrand in the Massif Central of France. This is of particular interest to me since I visited this site 35 years ago on a geology field excursion. The lavas are dated to 41,400 ± 2,000 years which in a geological context is very recent and were extruded during the peak of the last glaciation. I seem to recall that the volcanoes were still there, dormant (extinct?) and that the volcanic activity was linked to tectonic rotation of the Iberian peninsula. These lavas record the magnetic signature of the Laschamp Event.

At this point it is worth noting that a super volcanic eruption took place about 39,400 years ago close to Naples, Italy. It is not clear if there is a common process deep in the Earth giving rise to the temporary magnetic field reversal of the Laschamp Event and extreme volcanic activity in Europe. But it is clear that said volcanic activity will have impacted Earth’s climate at this time.

The Laschamp Event was a full reversal of Earth’s magnetic field that lasted only ~440 years and it took approximately 250 years to transition from normal to reversed polarity. This is amazingly rapid for such fundamentally important geological processes to occur. Looking back through the mist of geological time, such short lived events like this would become blurred noise against the main pattern of magnetic reversals (Figure 1).

According to Wikipedia, the reversed field was 75% weaker than Earth’s current magnetic field and that during the transition the field strength was 95% weaker than today. In other words, during the transition phase, Earth’s magnetic field dropped significantly, increasing exposure to the solar wind and cosmic rays. This would result in increased radiation levels at the surface which we know are non-lethal for life since we are still here.

This NASA source gives a somewhat different view saying:

Reversals take a few thousand years to complete, and during that time–contrary to popular belief–the magnetic field does not vanish. “It just gets more complicated,” (Figure 5).

But this statement is qualified by:

Earth’s present-day magnetic field is, in fact, much stronger than normal. The dipole moment, a measure of the intensity of the magnetic field, is now 8 × 1022 amps × m2. That’s twice the million-year average of 4× 1022 amps × m2.

Figure 5 Supercomputer model of Earth’s magnetic field. Normal state left and during a reversal right. It is ill advised to venture into the mountains with a map and compass when Earth’s magnetic field is in process of reversing! Source NASA (previous link).

We can conclude that Earth’s magnetic field is normally much weaker than at present. During reversals it becomes extremely complex and significantly weaker for very short periods during Laschamp type events, a notion supported by the greatly increased production of 10Be (Figure 2).

The risks to human society from Laschamp type events stems from possible climate change and in the modern world, negative impacts on satellites and electronic equipment that are susceptible to damage from ionising radiation. In the recent past, this has only been a concern during solar storms that manage to penetrate Earth’s magnetic defences. With those defences down, Earth would be more continuously exposed to such electro magnetic risk and solar storms would represent an increased risk to electrical systems on Earth.

Recent history

Earth’s magnetic north pole was first established by explorer James Ross in 1831 and was then located in the island archipelago of northern Canada (Figure 6). 73 years later it was located once again by Roald Amundsen who found that it had moved 50 kms in those 73 years (0.69 kms / year). But then it began to motor, heading “N” out into the Arctic basin:

The pole kept going during the 20th century, north at an average speed of 10 km per year, lately accelerating “to 40 km per year,” says Newitt. At this rate it will exit North America and reach Siberia in a few decades.

(source NASA)

Figure 6 Earth’s N magnetic pole has decided to go walkabout since 1904 and is heading for Siberia at a rate of 60 km / year according to Phil Chapman.

The European Space Agency (ESA) seems to have woken up to the importance of our magnetic field, saying:

The field can be thought of as a huge bubble, protecting us from cosmic radiation and charged particles that bombard Earth in ‘solar winds’. Without this protective shield, the atmosphere as we know it would not exist, rendering life on Earth virtually impossible.

This combined with ground observations of a wandering pole and weakening field strength appears to have prompted ESA to launch the Swarm Magnetic Field Mission that saw three satellites equipped with magnetometers launched in November 2013.

The satellites have been collecting data for only six months and we therefore need to be cautious in interpreting the data since there is no baseline of “normal behaviour” against which the results summarised in Figure 7 should be compared.

Figure 7 Changes measured by the Swarm satellite over the past 6 months shows that Earth’s magnetic field is changing. Shades of red show areas where it is strengthening, and shades of blue show areas that are weakening. Image from Scientific American. Data from ESA.

Sceintific American goes on to say:

While changes in magnetic field strength are part of this normal flipping cycle, data from Swarm have shown the field is starting to weaken faster than in the past. Previously, researchers estimated the field was weakening about 5 percent per century, but the new data revealed the field is actually weakening at 5 percent per decade, or 10 times faster than thought. As such, rather than the full flip occurring in about 2,000 years, as was predicted, the new data suggest it could happen sooner.

The Carrington Event

What I have written here is not to be confused with the Carrington Event of 1-2 September 1859 when the Sun spat out a coronal mass ejection (gigantic solar flare) directly at Earth. The flare seemed to be aimed at Earth and this led to speculation about a Sun-Earth connection. Wikipedia writes:

On September 1–2, 1859, the largest recorded geomagnetic storm occurred. Aurorae were seen around the world, those in the northern hemisphere even as far south as the Caribbean; those over the Rocky Mountains were so bright that their glow awoke gold miners, who began preparing breakfast because they thought it was morning. People who happened to be awake in the northeastern US could read a newspaper by the aurora’s light. The aurora was visible as far from the poles as Cuba and Hawaii.

and

Telegraph systems all over Europe and North America failed, in some cases giving telegraph operators electric shocks. Telegraph pylons threw sparks. Some telegraph systems continued to send and receive messages despite having been disconnected from their power supplies.

Carrington type events, therefore, are linked to solar activity but are relevant to this post since a significantly weakened magnetic field on Earth may render Earth more susceptible to the impacts of hightened solar activity. Solar geomagnetic activity is also in decline as the Sun marches towards a Grand Solar Minimum and I’m unsure whether this increases or reduces the chance of explosive mass ejections.

Electricity grids on Earth were built during the first half of the 20th Century and communications satellites are a feature of the second half of the 20th Century. All of this electrical infrastructure has been deployed at a time when Earth’s magnetic field was anomalously strong – “twice the million year average”. It seems possible that we may now be marching towards a period when the magnetic field is less than half the million year average.

Consequences

As Phil Chapman points out, the current march of the N magnetic pole towards Siberia may fizzle out and a new stability established. Alternatively, it may continue and in a few decades time our magnetic field may become weakened and disorganised (Figure 5) with auroras all over the planet. What might the consequences be?

Climate change: A decline in Earth’s magnetic field will lead to greater exposure to cosmic rays and greater exposure to the solar wind and solar flares. Cosmic rays may or may not result in enhanced nucleation of low clouds. Anthony Watts has a recent update on Svensmark’s work here. Sceptical Science remains sceptical here.

What we do know is that in the GISP 2 ice core there appears to be a correspondence between cosmic ray flux and temperature variations (Figure 2) and similar co-variance of cosmogenic isotopes and climate impacts have been described for the Holocene (refs 1, 2, 3, 4). These may also be explained by spectral variations in solar radiation that may or may not influence ozone production in the stratosphere.

My gut feel is that increased exposure to the solar wind would likely have some climatic impact that is as yet not understood. I’m hoping some commenters may cast some light on the possibilities.

Satellite communications: Industrial society has become heavily dependent upon satellites for communications, navigation, defence and entertainment. Satellites are already subject to damage from solar flares with Earth’s defences fully in place. With significant reduction in Earth’s magnetic field over the next 10 decades or so I would suspect severe damage to the satellites our everyday lives depend upon. Of course, ageing satellites may be replaced with ones that are better shielded from solar and cosmic radiation.

Electricity grids: Electricity grids and electronic equipment are exposed to disruption from increased solar electromagnetic storms. The Carrington Event lasted only a couple of days. The fall in Earth’s magnetic field, when it comes, may last for hundreds of years.

There could be exciting times ahead.

References

[1] Gerard Bond et al (2001) Persistent Solar Influence on North Atlantic Climate During the Holocene VOL 294 SCIENCE

[2] U. Neff et al (2001) Strong coherence between solar variability and the monsoon in Oman between 9 and 6 kyr ago NATURE | VOL 411 | 17 MAY 2001

[3] Debra A. Willard et al (2005) Impact of millennial-scale Holocene climate variability on eastern North American terrestrial ecosystems: pollen-based climatic reconstruction Global and Planetary Change 47 (2005) 17–35

[4] Andre E. Viau Widespread evidence of 1500 yr climate variability in North America during the past 14 000 yr Geology; May 2002; v. 30; no. 5; p. 455–458