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Expeditions show: The Arctic is as warm as never before in the last 7500 years

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25.08.2022 | Majken Grimm | News WSL



In the past 7500 years, it has never been as warm in the Arctic as it is now. A unique collection of tree ring samples that were gathered in more than 20 expeditions shows that. The new study with participation of the Swiss Federal Institute for Forest, Snow and Landscape Research WSL has been published in “Nature Communications”.


In the Yamal peninsula in the Arctic, erosion uncovers ancient trees that are witnesses of another time. Thanks to the tree rings, they can be dated and the climate of past millennia reconstructed. Researchers have now managed to create a continuous chronology that goes back to the year 5618 BC. This makes it the longest tree ring chronology from the Arctic region.

The study shows the extent of climate change: In the entire period covered, it has never been as warm in the Arctic as in the last 30 years. Until 1850, the climate was cooling steadily. The warming since the industrial revolution exceeds any natural variation.


The result of many expeditions

The approach allows an accurate reconstruction of the climate because the tree rings are directly related to the temperatures of the summer, which severely limit the annual growth of the trees in Yamal peninsula.

It took more than 20 expeditions over a period of 40 years to gather enough wood samples. Since there are no roads in Yamal peninsula, the researchers moved around by boat on the rivers. From the river sediments, they dug out trees and sawed them up to take samples. These were examined in the laboratory and compiled into a continuous series of data.

The rivers on Yamal peninsula are continuously in motion and transport sediment and rocks with them, which can cause trees on the banks to fall into the river. If these are then covered by sediment, the permafrost can preserve them for a long time.


Tree rings testify to global warming

"Our surveys provide a unique basis to assess with annual resolution how unusually fast Yamal peninsula has warmed since 1850. The warming has reached temperature levels that are unprecedented during the last 7500 years," says Patrick Fonti from WSL. "These data help us to see the extent of current warming with a large time horizon."

In addition to the Swiss Federal Research Institute WSL, participants of the study were the Institute of Plant and Animal Ecology of the Ural Division of the Russian Academy of Sciences, the University of Geneva as well as the Climatic Research Unit of the University of East Anglia.