THE IMPACT OF PERMAFROST THAWING ON THE CARBON DYNAMICS OF TUNDRA

There is debate on the potential release of the tundra's immense carbo n stocks into the atmosphere in response to global warming. We present here results obtained with a model of CO2 exchanges, coupled to a mod el of the soil thermal and hydrological regime in the tundra. We show that, because of the partial thawing of permafrost and subsequent incr ease in nutrient availability, the ecosystem's response to warming may be a long-lasting increase in C accumulation, following a temporary i ncrease in CO2 emissions. Our study also provides a consistent picture of CO2 exchanges in tundra ecosystems, reconciling the short-term exp erimental response to warming, recent field measurements, and Holocene C accumulation estimates.