This paper discusses radiocarbon in CO₂ and soil organic carbon from Arctic Alaska. From soil chamber measurements, we observed strong seasonal and spatial patterns in 14C of ecosystem respiration, which declined throughout the summer and differed among permafrost features. Radiocarbon in pore-space CO₂ indicated decomposition of carbon as old as 3000 years near the permafrost table. Together, these data reveal different rates of old carbon decomposition from distinct permafrost features.