Scientists Discovered Late Antique Ice Age Was Not Global

Map of the study areas and examples of three anomalous anatomical structures.
Photo Credit: Monika Grabkowska

The international group of scientists, which includes Ural dendrochronologists, found that between 536 and 550 years the temperature decreased only in the Northern Hemisphere. Scientists obtained data on trees in Eurasia, the Western and Southern Hemispheres. The results were published in Science Bulletin. The work was supported by the Russian Science Foundation (project No. 21-14-00330).

"We estimated the spatial scale of the events of the 536-540s using tree rings. We used "abnormal" rings as markers. One advantage of the approach is that the width of the annual rings responds to temperature changes mainly only in the polar regions and highlands, but abnormal rings form during extreme cold spells in trees in many regions of the Earth. Therefore, the work included data on 23 different points, including the Southern Hemisphere, that is much more than when using the width of the rings," says Rashit Khantemirov, co-author of the work, Leading Researcher of the Laboratory of Dendrochronology of the Institute of Plant and Animal Ecology, Ural Branch of the Russian Academy of Sciences, and Head Specialist of the Laboratory of Natural Science Methods in Humanities at Ural Federal University.

Scientists analyzed three types of anomalies: frost rings - rings with a layer of cells deformed due to freezing; light rings - with thin cell walls of late wood; blue rings - with reduced lignin content in the cell walls. All three types of anomalies form when the temperature drops rapidly and, as a rule, briefly (from several hours to several days) during the summer period. As a result, scientists found that not a single tree in the Southern Hemisphere had formed anomalies between 530 and 550.

"In the Northern Hemisphere, however, trees responded synchronously by forming anomalies of tree rings to the event of 536. Moreover, the peak of cooling, according to the annual rings, was at the end of July and the beginning of August. In some areas, anomalies were formed the next year as well. The cooling after the eruption of 540 was not synchronous. The duration was not the same in different regions. For example, in Mongolia, as well as the Yamal region, the extremum peak was in 543, in the USA in 541-543 and in Fennoscandia in 541-542", Rashit Khantemirov adds.

Scientists have long been discussing the causes of climatic cataclysms in the years 530-550. The most credible cause is considered a large volcanic eruption. However, for a long time in the ice cores of Greenland and Antarctica no traces of the eruption were found. This was probably due to the sparse data on the content of sulfates, which are markers of volcanic eruptions, and shortcomings in the dating of ice layers. But in 2008, an international team of researchers, including Danish researchers of glaciers and dendrochronologists from Europe and Russia, including Ekaterinburg, published data based on the width of the annual rings of trees. Dendrochronologists have established: the cooling, which began in 536, covered all of Eurasia and lasted about 15 years. Which is quite unusual, since even very large volcanic eruptions reduce the temperature for only 3-5 years. Scientists later found out that a few years later there was another eruption, which was one of the most powerful in the last two millennia.

"A very powerful eruption occurred four years later, in 540, and caused a climatic response due to the formation of a film of aerosol in the stratosphere. Therefore, its effects began to be felt in different areas of the Earth with a delay of 1-4 years. Further studies showed that the most likely source of the 540 eruption was the Ilopango volcano in central America. Such double volcanic impact led to an unusually long period of cold temperature", explains Rashit Khantemirov.

Reference:

Climatic and social cataclysms that began in 536 have long attracted the attention of volcanologists, climatologists and historians. Byzantine sources describe a mystical fog that covered a vast territory in 536-537. Cold and drought caused crop failures in Italy and Mesopotamia, causing famines and other disasters in the years that followed. The Justinian plague, the first historically known pandemic, claimed millions of victims at this time. Unusual phenomena have also been recorded in Chinese sources. In many provinces of China in July and August of 536, frost and snow were observed that killed crops and caused famine among the population, which lasted until 538. In the northern part of China, about 80% of the population died at that time. UrFU historians have shown: these events caused the Turks neighboring China to strengthen their position and subjugate their neighbors, which led to the formation of the Turkic Kaganate.

Source/Credit: Ural Federal University

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