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High Arctic wetting reduces permafrost carbon feedbacks to climate warming


The carbon (C) balance of permafrost regions is predicted to be extremely sensitive to climatic changes. Major uncertainties exist in the rate of permafrost thaw and associated C emissions (33-508 Pg C or 0.04-1.69 °C by 2100; refs,) and plant C uptake. In the High Arctic, semi-deserts retain unique soil-plant-permafrost interactions and heterogeneous soil C pools (>12 Pg C; ref.). Owing to its coastal proximity, marked changes are expected for High Arctic tundra. With declining summer sea-ice cover, these systems are simultaneously exposed to rising temperatures, increases in precipitation and permafrost degradation. Here we show, using measurements of tundra-atmosphere C fluxes and soil C sources (14C) at a long-term climate change experiment in northwest Greenland, that warming decreased the summer CO 2 sink strength of semi-deserts by up to 55%. In contrast, warming combined with wetting increased the CO2 sink strength by an order of magnitude. Further, wetting while relocating recently assimilated plant C into the deep soil decreased old C loss compared with the warming-only treatment. Consequently, the High Arctic has the potential to remain a strong C sink even as the rest of the permafrost region transitions to a net C source as a result of future global warming. © 2014 Macmillan Publishers Limited. All rights reserved.

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