Global research team date millennia-old magnetic storms using tree rings

A global team of scientists, along with the employees of the Krasnoyarsk Research Center of the Russian Academy of Sciences’ Siberian Branch and the Siberian Federal University managed to recover data on magnetic storms from thousands of years ago, the Russian Ministry of Science and Higher Education’s press service reported. The study was published in the Nature Communications journal.

“An international group of researchers, with the participation of the Krasnoyarsk Research Center of the Russian Academy of Sciences’ Siberian Branch and the Siberian Federal University have managed to pinpoint an increased concentration of stable carbon isotopes in tree rings from several samples of trees located on five continents, from 774 and 993 AD. These dates coincide with historical evidence indicating unusually bright northern lights (aurora borealis). This discovery not only proves the accuracy of the tree rings’ date patterns, but also, in the long run, it will help detect the frequency of abnormal magnetic storms of the past,” the message reads.

Earlier, Japanese scientists discovered that solar flares causing magnetic storms leave traces on tree rings. Heavy charged particles called protons enter the atmosphere and “enrich” the chemical elements forming part of it. Radiocarbon (a “heavy” carbon isotope 14C) is one of the products of this “enrichment”, which then becomes part of the carbon cycle on our planet: namely, it accumulates in trees. The researchers suggested that tree rings from the years with higher solar activity would include higher amounts of heavy carbon.

The Krasnoyarsk scientists, along with their foreign colleagues, decided to check this hypothesis. During the course of the research dubbed COSMIC, they analyzed tree samples from five continents, including trees from the Russian regions of Yamal, Taymyr, Yakutia and Tuva. The study found a significant increase of heavy carbon in all collected samples of tree rings from the summer of 774 and the spring of 993.

“We identified the recorded response in trees growing on five continents, in different ecologic zones, in the mountains and on the plains. We can say that this is a universal planetary response. Several historical sources confirm unusually bright lights in the sky during these years. Without a doubt, the scientists managed to discover traces of magnetic storms from the past,” the message states.

A senior researcher at the Siberian Federal University Alexander Kirdyanov explained that the exact dating of tree rings is necessary for climate reconstruction, as well as historical and environmental research. “As a result of this work, we have confirmed once again that by using tree rings, we can describe the past, the last several thousand years, within the precision of a year,” the researcher said.