Netherlands Polar Data Center

Extreme climatic events are increasing in frequency and intensity in the Sub-arctic, a rapidly warming region crucial to global carbon-climate feedbacks. Ecosystem carbon dioxide (CO₂) fluxes are profoundly impacted by extremes through both immediate and long-term legacy effects. As event intervals shorten, new extremes may coincide with incomplete recovery from previous ones; yet the consequences of multiple events remain poorly understood. We examined the recovery of tundra CO₂ fluxes relative to untreated controls following extreme drought, winter freezing and their combination. Mesocosms from two major sub-arctic ecosystem types, Sphagnum peatland and tundra heath, were subjected to a seven-week summer precipitation exclusion (2022) and subsequent winter freezing (- 20 °C for two weeks). Overall, our results reveal substantial and persistent legacy effects of (multiple) extreme events, potentially amplifying carbon-climate feedbacks.