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42,000-year-old trees can accurately analyze a magnetic field reversal on the earth



Ancient Kauri Tree Log

Ancient Kauri tree log from Ngawha, New Zealand. Image source: Nelson Parker

Radiocarbon measurements of residues from New Zealand kauri trees 42,000 years ago laid the foundation for better calibration of the geological archives of that period.

The last complete reversal of the earth’s magnetic field, the so-called Lachan event, occurred 42,000 years ago. Now, radiocarbon analysis of the residues of New Zealand kauri trees has made it possible for the first time to accurately time and analyze the event and its related effects, and to calibrate the sediments and sediments and other geological archives of the period. Simulations based on this show that the strong weakening of the magnetic field has a considerable impact on the earth’s atmosphere. An international team led by Chris Turney of the Australian University of New South Wales, Norbert Novazick of the German Earth Science Research Center in Potsdam and Florian of the Alfred Wegener Institute Adolf participated in an international study.diary science.

The earth’s magnetic field fluctuates permanently, and sometimes even reverses its polarity. Their causes, processes and effects are not yet fully understood. Now, researchers have investigated the so-called Laschamps incident in more detail. It refers to the last complete reversal of the earth’s magnetic field about 42,000 years ago. Not only did the magnetic field change its direction, it also caused a sharp drop in intensity over a period of hundreds of years.

About 42,000 years ago, the magnetic north pole moved south. In the course of about 500 years, the magnetic field weakened to 6% to 0%. In about 500 years, the two poles kept reversing, and the field strength changed below 28% of today, but it took about 250 years to reverse again.

Old kauri tree logs from Newark, New Zealand

Ancient Kauri tree log from Ngawha, New Zealand. Image source: Nelson Parker

Now, this precise time classification can be performed by linking different data sets. First, the researchers used the results of the Earth’s magnetic field obtained by Norbert Nowaczyk and his team from sedimentary cores in the Black Sea since 2013. These results matched the Greenland ice cores through simultaneously recorded climate changes.

Secondly, only through the analysis of radiocarbon (14C) can the event be accurately analyzed and dated. During this period, the fossil kauri tree grew in the wetlands of Ngawha in northern New Zealand for about 1700 years. It was then well preserved in the swamp.

Chris Turney reported this discovery about 40,000 years ago when visiting the German Center for Geosciences (GFZ) in Potsdam a few years ago. “As a geomagnetic scientist, I immediately thought of the link related to the Laschamps incident and proposed a 14C analysis, which had not been performed on trees at the time,” said Novazic, who was in charge of the Paleomagnetic Rock Laboratory at the time. People GFZ.

Background: With the weakening of the magnetic field, the earth has at least partially lost its important protective layer against cosmic radiation. This is also reflected in the increase in the content of radiocarbon isotope 14C in trees. The reason is that the formation of 14C in the earth’s atmosphere increases during the bombardment of nitrogen by high-energy, charged cosmic particles.

“Sub-fossil kauri trees are an exciting archive of atmospheric composition,” said Florian Florian, a paleoclimatologist at the Alfred Wegener Institute of the Helmholtz Center for Polar and Ocean Research (AWI). Adolf said. These trees can survive for thousands of years, and as they grow to record annual changes in the radiocarbon content of the atmosphere, the research team made precise measurements.

These data have improved the calibration curve for radiocarbon dating, allowing more accurate dating of various climate archives and fossils. They can also be compared directly with ice cores: the beryllium isotopes measured there show changes similar to the radiocarbon in trees, because the production of both isotopes in the Earth’s atmosphere depends on the intensity of the cosmic rays that hit the earth. “-Author. He uses this effect to synchronize trees and ice cores with high precision, and reduces the uncertainty of comparing the two files from thousands of years to about 100 years.

In order to study the further influence of the weak earth’s magnetic field on the atmosphere and on the global climate, the researchers performed atmospheric chemistry simulations. Among other things, they found that ozone was reduced. Turney explained: “Unfiltered radiation from space is destroying air particles in the Earth’s atmosphere, separating electrons and emitting light. This process is called ionization.” “Ionized air makes the ozone layer “sizzle.” This triggered a wave of atmospheric changes, including increased glare indicating what we call the Northern Lights, which may have been observed not only near the poles but also on a global scale.

Nowaczyk said that in view of the current development, it is very important to further analyze the influence of the weak magnetic field in this direction. Because the earth’s magnetic field has been weakened for about 2000 years. Compared with the first direct measurement 170 years ago, the observed value in the South Atlantic has dropped by 9%, or even by 30%. Whether this means that the polar reversal in the next one to two thousand years is about to occur, it remains to be discussed. However, the collapse of natural radiation shielding will pose a huge challenge to today’s society, because today’s society is largely based on electronic technology.

On the basis of these new possibilities of chronologically categorized events 42,000 years ago, the lead author of the study proposed more far-reaching hypotheses about the impact of the Earth’s magnetic field reversal, such as the hypothesis of the demise of the Earth’s magnetic field. The occurrence of Neanderthal or cave paintings. Nowaczyk does not rule out the possibility of causality here, but believes that the possibility is very small.

For more information on this research, please read “The Earth’s Magnetic Field Reversal Caused a Global Environmental Crisis 42,000 Years Ago.”

Reference: “Alan Cooper, Chris SM Turney, Jonathan Palmer, Alan Hogg, Matt McGlone, Janet Wilmshurst, Andrew M. Lorrey, Timothy J. Heaton, James M. Russell, Ken McCracken, Julien” The Global Environmental Crisis 42,000 Years Ago “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 Nowac , Eleanor Rainsley (Eleanor Rainsley), Christopher Bronk Ramsey (Christopher Bronk Ramsey), Paul Sebastianelli (Paolo Sebastianelli), Yassine Suimi (Yassine Souilmi, Janelle Stevenson, Zoë Thomas, Raymond Tobler and Roland Zech, February 19, 2021 , science.
DOI: 10.1126/science.abb8677




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