Amid an unusually warm and dry stretch in the Arctic this summer, wildfires have raged across Alaska, Greenland and Siberia, posing a threat to sea ice. Climate scientists aren’t concerned about the presence of wildfires, but rather with their length and intensity.

The Copernicus Atmosphere Monitoring Service, a European forecasting organization, noted more than 100 “intense and long-lived wildfires” above the Arctic Circle since June. These fires emitted as much carbon dioxide as the country of Sweden does in an entire year. That matches the emissions from all June Arctic wildfires between 2010 and 2018, combined.

A major concern for longer and stronger wildfires is the smoke that drifts over the Arctic sea and land ice, hastening its melt. The U.S. National Oceanic and Atmospheric Administration announced that sea ice cover in the Arctic has dropped to the second-lowest level on record for the month of June. With the melt season continuing until September, it may be headed for a record low.

Darker ocean water is exposed when sea ice melts, which absorbing sunlight and causing water temperatures to rise. That exposure has led the Arctic to warm at more than twice the rate of the rest of the world.