News – PH – 42000 year old trees allow a precise analysis of the last magnetic field reversal on earth


Radiocarbon measurements on the remains of 42000 year old New Zealand kauri trees form the basis for a better calibration of geological archives of this time

The last complete reversal of the earth’s magnetic field, the so-called Laschamps event, took place before 42000 years ago, instead of radiocarbon analyzes of the remains of kauri trees from New Zealand, it is now possible for the first time to precisely measure and analyze this event and the associated effects, as well as to calibrate geological archives such as sediments and ice cores from this period.Simulations based on this show that the strong reduction in the This shows an international team led by Chris Turney from the Australian University of New South Wales with the participation of Norbert Nowaczyk from the German Research Center for Geosciences Potsdam and Florian Adolphi from the Alfred Wegener Institute in a study, which now appears in the journal Science

The earth’s magnetic field is subject to permanent fluctuations and occasionally even polarity reversals occur. Their causes, their course and effects are not yet fully understood Researchers have now examined the so-called Laschamps event in more detail.It refers to the last complete reversal of the polarity of the earth’s magnetic field about 42000 years ago The magnetic field not only changed direction, it also lost strength dramatically over a period of several hundred years

About 42During this process, which lasted about 500 years, the magnetic field weakened to six to zero percent. Over a period of about 500 years, the poles remained reversed, with a field strength below 28 percent of the today’s value varied, only to be reversed in the course of about 250 years

This precise chronological classification is now possible by linking different data sets.First, the researchers used results on the geomagnetic field of sediment cores of the Black Sea by Norbert Nowaczyk and his team from 2013, which were compared with Greenland ice cores using simultaneously documented climate variations

Second, accurate analysis and dating of the events was only made possible by radiocarbon (14C) analysis of a subfossil kauri tree that grew in the wetlands of Ngawha in northern New Zealand over a period of around 1700 years and was subsequently very well preserved in the swamps

Chris Turney had a few years ago during a visit to the German Research Center for Geosciences in Potsdam (GFZ) about 40“As a geomagnetic scientist, I immediately had a connection to the Laschamps event and suggested 14C analyzes that had not yet been carried out on trees at that time,” says Nowaczyk, head of the laboratory for paleo- and rock magnetism at the GFZ

The background: With the disappearance of the magnetic field, the earth at least partially loses an important protective shield against cosmic radiation.This is also reflected in the increased levels of the radioactive carbon isotope 14C in the trees.The reason for this is the increased formation of 14C in the earth’s atmosphere during the bombardment of nitrogen by energetic, electrically charged cosmic particles

“The subfossil kauri trees are an exciting archive of atmospheric composition,” says Florian Adolphi, paleoclimatologist at the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) These trees can live for several thousand years and, as they grow, record annual fluctuations in atmospheric radiocarbon content, which the research team accurately measured

“These data improve the calibration curve for radiocarbon dating and enable a more precise dating of a large number of climate archives and fossils. They also enable a direct comparison with ice cores: The beryllium isotopes measured there show similar variations as the radiocarbon in the trees, since the production of both Isotopes in the earth’s atmosphere depends on the intensity of the cosmic rays falling on the earth, ”explains the study author. With this effect, he synchronizes trees and ice cores with high precision and reduces the uncertainty when comparing the two archives from several thousand years to around 100 years

In order to investigate further effects of the weak earth’s magnetic field on the atmosphere and thus also on the global climate, the researchers carried out simulations of atmospheric chemistry. They found, among other things, a decrease in ozone. “Unfiltered radiation from space, decomposed air particles in the earth’s atmosphere, separated electrons and emitted light – a process known as ionization, “explains Turney.” The ionized air “sizzled” the ozone layer, causing a wave of changes in the atmosphere, including increased glare we know as the aurora borealis, which too this time may have been observed not only near the poles but all over the world

In view of current developments, it is important to further analyze the effects of the weak magnetic field in this direction, says Nowaczyk.Because the earth’s magnetic field has been weaker for about 2000 years, compared to the first direct measurements 170 years ago, a weakening of nine Percent observed, in the area of ​​the South Atlantic even thirty percent. Whether this means that a pole reversal is in sight for the next one to two thousand years is controversial A collapse of natural radiation protection would, however, represent a major challenge for our society today, which is heavily dependent on electronics based

Based on these new ways to chronologically classify events prior to 42nd000 years ago, the main authors of the study put forward even more far-reaching hypotheses about the effects of the Earth’s magnetic field reversal – for example with regard to the extinction of the Neanderthals or the beginning of cave paintings Nowaczyk does not rule out the possibility of causal connections here, but considers this to be rather unlikely >

For more information on this research, see Earth Magnetic Field Reversal Before 42000 years ago that triggered a global environmental crisis

Reference: “A global environmental crisis before 42000 years ”by Alan Cooper, Chris S M. Turney, Jonathan Palmer, Alan Hogg, Matt McGlone, Janet Wilmshurst, Andrew M Lorrey, Timothy J. Heaton, James M Russell, Ken McCracken, Julien G Anet, Eugene Rozanov, Marina Friedel, Ivo Suter, Thomas Peter, Raimund Muscheler, Florian Adolphi, Anthony Dosseto, J Tyler Faith, Pavla Fenwick, Christopher J. Fogwill, Konrad Hughen, Mathew Lipson, Jiabo Liu, Norbert Nowaczyk, Eleanor Rainsley, Christopher Bronk Ramsey, Paolo Sebastianelli, Yassine Souilmi, Janelle Stevenson, Zoë Thomas, Raymond Tobler and Roland Zech, 19 February 2021, WissenschaftDOI: 101126 / Wissenschaftabb8677

If Turney can’t tell us how a plasma affects UV transmission, his speculations may be premature. In any case, I strongly suspect that any UV-C that has made it through the stratosphere creates ozone at lower altitudes and being absorbed in the process So there would be temperature changes in the upper troposphere, but I don’t think there would be UV fluxes much larger than what humans and animals are experiencing in the Himalayas today. Melanomas are more of a problem in Australia than melanomas in Tibet

SciTechDaily: Home of the Best Science and Technology News Since 1998. Stay up to date on the latest Scitech news via email or social media

On board the Juno spacecraft, an instrument led by the Southwest Research Institute that was observing aurors accidentally spotted a bright flash over Jupiter’s clouds last spring The UV Spectrograph …

Earth’s magnetic field, earth, neanderthal, geomagnetic inversion, magnetic field

News – PH – 42000 year old trees allow a precise analysis of the last magnetic field reversal on earth