Mid- to late-Holocene carbon balance in Arctic Alaska and its implications for future global warming

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Abstract
In the event of global warming, there is considerable uncertainty whether northern ecosystems will act as an atmospheric CO2 sink or source. This study examines Holocene rates of soil carbon accumulation along a latitudinal transect in northern Alaska as an analogue for future change in the Arctic. Rates of carbon accumulation during the colder late-Holocene (4800-400 BP) varied from 1.2 to 3.5 g C m-2 yr-1. During the warmer mid-Holocene (6900-4800 BP), the rate of carbon accumulation at Prudhoe Bay was significantly higher (6.7 g C m-2 yr-1) than during the colder late-Holocene (1.2 g C m-2 yc-1). Both paleoclimatic and latitudinal trends support the argument that long-term carbon storage in far-northern ecosystems (arctic and subarctic) increases with increasing temperature. This suggests that far-northern ecosystems will, over the long term (centuries to millenia), continue to act as a small sink (0.034-0.070 Gt yr-1) for atmospheric CO2 following global warming, which will provide a small negative feedback on global warming. However, recent studies also suggest the possibility that over the short term (decades to centuries), overall carbon loss from the Arctic might also provide a strong positive feedback on global warming.