Nature Communications, 23 March 2022
Extreme summer rainfall can increase the depth of permafrost thaw by over 30% in the northeastern Siberian tundra, an Arctic region characterized by its thick, frozen ground. Periods of intense rainfall allow warm water to seep downward and transport heat into frozen soils, accelerating permafrost thaw. The effects of extreme rainfall and intense thaw can persist over multiple years, because it destabilizes the top layer of permafrost and delays seasonal refreezing of these soils. Under a high-emissions scenario, precipitation in the Arctic is projected to increase by up to 60% by 2100; and increasingly shift from snow to rain due to rising air temperatures. Thawing permafrost can release huge amounts of stored carbon dioxide and methane into the atmosphere, further intensifying climate warming. These findings emphasize the urgency of curbing global temperature rise to 1.5°C to preserve as much frozen permafrost as possible; and mitigate long-term committed carbon emissions from thawed permafrost.