During the existence of the Earth, the north and south magnetic poles have repeatedly changed places. Theoretically, this can happen now - at any time. To imagine the consequences, scientists for the first time reconstructed in detail what was on the planet at the last pole flip, 42 thousand years ago.
The magnetic north pole, which the compass needle points to, is constantly shifting, so any of its coordinates are temporary and inaccurate. After the English polar explorer James Ross first recorded the magnetic pole in the area of the islands of the Canadian archipelago in 1831, it moved strongly and is now located in the central part of the Arctic Ocean, continuing to drift towards the Russian Arctic coast. The South Pole is not standing still either.
This is explained by the processes taking place in the core of the Earth. It is believed that its outer part consists of liquid metals, they are mixed, there is an electric current and, accordingly, a magnetic field. This is called a magnetic dynamo.
Recently, researchers from the UK and Denmark analyzed data from the European Space Agency's Swarm satellites over the past two decades and found that the position of the magnetic poles is determined by the ratio of deep magnetic fluxes forming at the core.
Since the 1990s, the magnetic north pole has quadrupled and now travels about 65 kilometers a year. At the same time, the magnetic field on average over the planet loses 20 nanotesla per year, that is, it weakens by five percent per century. This happens, of course, unevenly - somewhere the field is getting stronger. But in general has decreased by ten percent over the past 150 years. This is an alarming signal.
Dangerous polarity reversal
There have been several hundred magnetic pole reversals in the history of the Earth. Moreover, no pattern can be seen here. For example, a hundred million years ago, the polarity did not change for almost 40 million years. And the last inversion, which occurred about 42 thousand years ago and was called the Lashamp excursion around a place in France, was very short - the poles literally immediately by geological standards - within several hundred years - returned to their previous position.
But this turned out to be enough to cause abrupt climate changes and a whole series of consequences, dramatic for all living things.
Recently, the results of the first of its kind research were published that reconstruct the events associated with the excursion of Lashamp from indirect data. Scientists from Australia, New Zealand, England, USA, Switzerland, Sweden, Germany, China and Russia took part in the work.
The starting point was the huge fossilized cowrie tree trunks discovered in the north of New Zealand, which had lain in peat soils for 41-42 thousand years. After analyzing the width and composition of the growth rings, scientists made conclusions about the features of the environment for 1700 years - immediately before and during the excursion of Lashamp.
"We also studied the chronicle of the magnetic field in rocks, traces of cosmic radiation in the ice of Antarctica and Greenland and other traces of the processes of that time. Thanks to the growth rings, we clarified the dating and synchronized data from different sources," - a press release from the Russian Science Foundation, which supported the study a grant, cited the words of Evgeny Rozanov, a geophysicist from St. Petersburg State University and the Physico-Meteorological Observatory in Davos (Switzerland), who was responsible for mathematical modeling in the project.
Scientists have found that for about one and a half thousand years, the Earth's magnetic field was decreasing, which means that the protection of the planet's surface from the flow of ionized particles - the solar wind and cosmic rays - weakened. It was calculated that when the polarity is reversed, this protection decreased by 90 percent … This confirms the ratio of isotopes of carbon, beryllium and oxygen in the ice layers of that era.
Looks like the end of the world
A number of solar activity minima are observed in the same period. In combination with a weak geomagnetic field, this created the conditions for a "perfect storm" - Much more cosmic radiation was reaching the Earth than before. The ozone layer was destroyed, the plant and animal world of the planet was exposed to harsh ultraviolet radiation.
Nature changed - for example, Australia turned into a desert, many species of animals and plants became extinct. It is no coincidence that the Neanderthals disappeared around the same time, and people of the modern type, representatives of the Aurignacian culture, began to live in caves.
Researchers have developed a detailed chemical-climatic model of the Earth's atmosphere, taking into account various internal and external factors, including the circulation of matter and heat exchange, chemical processes and nuclear reactions in the upper layers.
Modeling showed that during the Lashamp excursion, the amount of ozone above the Earth's surface fell by about five percent, and at low latitudes - by 10-15. The ultraviolet flux increased by the same amount, especially in the equator region. The ionization of the stratosphere jumped by several orders of magnitude, and the aurora covered the entire planet.
The global climate system has changed: it has warmed in Northern Europe and northeast Asia, while it has become colder in North America. In low latitudes, cloudiness increased sharply and thunderstorms became more frequent - electric storms continuously appeared in the ionized air, which perfectly conducts electricity.
"It looked like the end of the world"- quoted the head of the study, Professor Alan Cooper of the South Australian Museum of Natural History in Adelaide, the press office of the University of New South Wales
Foresight by Douglas Adams
The most dramatic situation was not at the moment of the actual reversal of the poles, but several hundred years before that, 42,300-41,600 years ago, when the magnetic field strength dropped to about six percent of today's value
It was called the "Adams' transient geomagnetic event" after the English science fiction writer Douglas Adams. In The Hitchhiker's Guide to the Galaxy, he wrote that the number 42 is "the answer to the main question of life, the Universe and all that."
Scientists for the first time directly link magnetic pole reversal to large-scale changes in nature, and did so on the basis of precise radiocarbon analysis. Prior to that, it was believed that geomagnetic fluctuations practically do not affect the climate and biosphere of the Earth.
The current weakening of the magnetic field, according to the authors of the study, may indicate the approach of the next inversion. For modern civilization, with its electronic equipment and orbiting satellites, very sensitive to cosmic radiation, the consequences can be much more serious than for our cave ancestors.