Arctic tundra ecosystems in Alaska are releasing carbon dioxide (CO2) due to thawing permafrost, which can contribute to climate change. Recent studies show that these ecosystems are currently losing CO2, especially during warm autumns. The amount of CO2 lost is related to the timing of soil freeze-up in the fall. This loss of carbon translates to about 4.1% in wet sedge tundra and 1.4% in heath tundra from 2008 to 2015. Rising air and soil temperatures may lead to even more CO2 release, which could worsen global warming if it happens in other Arctic areas.