Behind the Cover: January 2023

Each month, Physics Today editors explore the research and design choices that inspired the latest cover of the magazine.

Wildfires burn even across the snow- and ice-covered Arctic. Two papers on the topic, published in a November issue of Science, attracted the attention of our editorial team and are the subject of a story in this month’s issue . The high-latitude blazes are fueled by carbon-rich permafrost and are adding more carbon dioxide to the atmosphere, accelerating the region’s warming.

The cover image, first acquired by the European Space Agency, shows peatlands that are usually permanently frozen burning across a 3-km-wide stretch of Arctic tundra on 18 June 2020. Adrià Descals, of the Centre for Ecological Research and Forestry Applications in Spain, overlaid the true-color image with an IR filter to indicate the locations of individual fires.

Descals and his colleagues found that Arctic wildfires were especially pervasive recently. The total area of the Siberian Arctic is some 286 million hectares, and 9.2 million hectares of it burned between 1982 and 2020. Wildfires occurring in 2019–21 alone were responsible for almost half of the area burned over the past 40 years. Descals and his colleagues discovered that average summer air temperatures in 2019–21 exceeded 10 °C, a full 2 °C warmer than the historical average.

Another research team, led by Rebecca Scholten of Free University of Amsterdam, analyzed the timing of snowmelt in the Arctic spring and learned that snow melted an average of four to eight days earlier in 2020, relative to the data set’s average over 2001–21. The researchers suspect the earlier snowmelt occurred, in part, because of an increase in the frequency of an atmospheric circulation pattern that causes drier conditions more favorable to wildfire.