Five of the ten largest forest fires in the modern history of California raged in 2020. And also in 2021, huge fire called Caldor, Dixie or River Complex, who charred tens of thousands of quadractilometers for forest and bush and caused economic damage of several billion dollars. These fire were favored by persistent drought in the western United States, which was only alleviated by extensive rainfall in parts of California in mid -October. The frequent occurrence of strong drought and extreme fire weather locations in the region could in turn related to the ice loss in the Arctic, Youfei Zou from the Pacific Northwest National Laboratory and his team in "Nature Communications".
For their study, the scientists had combined data on forest fires, the sea ice cover in the Arctic and weather conditions over the west of North America and calculated models that combined all three factors in an interplay. The simulations showed a strong correlation between the dwindling sea ice in the period from July to October and an increased risk of extensive forest fires between September and December: the smaller the ice cover, the greater the fire risk.
When dark sea water spreads to the disadvantage of light ice surfaces, this influences large -scale circulation patterns in the atmosphere: in western North America, strong and persistent high -pressure areas can spread that bring hot and above all dry weather. For example, such a heating bell was set up again in the summer of 2021 and parts of Canada's record temperatures and intensive forest fires.
Zou and Co conclude that this effect has a similarly strong effect on the risk of forest fires as the already known consequences of El Niño, which influences the weather globally: While it can rain abundantly on the otherwise dry South American Pacific coast, drought prevails in Indonesia, Australia or California. "Extreme fire weather and increased risk of large wildfires are part of the new normal in regions like California," the scientists write. And conditions could get worse by 2050 due to the predicted further loss of ice in the Arctic.
