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The nitrogen stock of the ice-rich yedoma domain

Abstract

Recent studies on permafrost organic matter (OM) suggest that a portion of previously frozen carbon will enter the active carbon cycle as high latitudes warm. Less is known about the fate of other OM components, including nutrients such as nitrogen (N). The abundance and availability of N following permafrost thaw will regulate the ability of plants to offset carbon losses. Additionally, lateral N losses could alter aquatic food webs. There is growing evidence that some N is lost vertically as N2O, a greenhouse gas 300 times stronger than CO2 over 100 years. Despite broad recognition of its role regulating both carbon and non-carbon aspects of the permafrost climate feedback, estimates of permafrost N remain uncertain. To address this knowledge gap, we quantified N content for different stratigraphic units, including yedoma, Holocene cover deposits, refrozen thermokarst deposits, taberal sediments, and active layer soils. The resulting N estimates from this one permafrost region were similar in magnitude to previous estimates for the entire permafrost zone. We conclude that the permafrost N pool is much larger than currently appreciated and a substantial pool of permafrost N could be mobilized after thaw, with continental-scale consequences for biogeochemical budgets and global-scale consequences

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