Nearly 42,000 years ago, when the Earth’s magnetic fields turned around, it caused major environmental changes, extinction events, and prolonged changes in human behavior, a new study reports.
The findings, made possible by a new radiocarbon record derived from New Zealand’s ancient kauri trees, raise important questions about the evolutionary impact of geomagnetic reversals and excursions in the deeper geological report.
‘Before this work,’ says author Chris Turney in a related video, ‘we knew a lot of things were happening around the world 42,000 years ago, but we did not know exactly how … for the first time could date exactly what happened when the earth’s magnetic fields last turned around. ”
In the geological report, there are numerous cases where the planet’s magnetic poles have reversed. Today, such an event would almost certainly wreak havoc with modern electronics and satellite technologies. However, the potential environmental impacts of such events are virtually unknown.
The most recent magnetic inversion, the Laschamps Excursion, a relatively short-lived geomagnetic event that took place ~ 41,000 years ago, offers one of the best opportunities to study the potential effects of extreme changes on the Earth’s magnetic field. Despite compelling evidence from several pole-environmental records suggesting that it coincided with significant environmental and ecological changes, the ability to accurately characterize this event and determine its role – if any – in temporary global changes is limited by ‘ an uncertain radiocarbon calibration for the period.
In this study, Turney, Alan Cooper and colleagues present a new, precisely dated atmospheric radiocarbon record derived from the tree rings of ancient kauri trees preserved for millennia in New Zealand wetlands. Like a missing keystone, this author has enabled the authors to better align other global radiocarbon and iron core records with the Laschamps.
Cooper et al. identified a significant increase in atmospheric radiocarbon during the attenuation of the magnetic field strength that preceded the reversal of polarity. By modeling the effects of this increase, they found that the minimum geomagnetic field, when the Earth’s magnetic field was only ~ 6% of current levels, caused significant changes in atmospheric ozone concentration and circulation.
These shifts may have caused synchronous global climate and environmental changes observed in other climate records ~ 42,000 years ago. The discovery that geomagnetic field fluctuations can affect the temperature and circulation of the world is a model for understanding abnormal and sudden shifts in the environment.
Reference: ‘A Global Environmental Crisis 42,000 Years Ago’ by 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 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, February 19, 2021, Science.
DOI: 10.1126 / science.abb8677