For millennia, the tundra regions of the Arctic drew in carbon from the atmosphere and locked it in permafrost. That is the case no more, according to an annual report issued on Tuesday by the National Oceanic and Atmospheric Administration.

Increasingly frequent and severe wildfires have become a yearly concern for many Arctic communities, and a chapter of a new U.S. report involving one Canadian university—Université de Montréal—suggests that they are also having a significant impact on carbon emissions in the region.