Climate-carbon feedback tradeoff between Arctic and alpine permafrost under warming

Whether greenhouse gas (GHG) emissions from permafrost will trigger positive climate feedbacks under warming remains unknown. Here, we synthesized the response of growing season carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) emissions to experimentally manipulated warming of ~2°C for permafrost in alpine and Arctic regions. Warming weakened the GHG sink of alpine permafrost, thereby increasing (13%) its global warming potential, but strengthened the GHG sink of Arctic permafrost and decreased (-10%) its global warming potential. When warming caused drying of alpine permafrost soils, the CO₂ sink weakened but the CH₄ sink increased. In contrast, warming of relatively wet Arctic permafrost increased the CO₂ sink and CH₄ source. Warming led to much stronger increases of the N₂O source in alpine than Arctic permafrost. Although keeping additional warming below 2°C in permafrost regions can avoid the positive permafrost-climate feedback, measures are needed to maintain fragile carbon sink of alpine permafrost ecosystems.