Thaw-induced release of carbon from permafrost in Eastern Siberia during the last deglaciation

Gesine.Mollenhauer [ at ]


Permafrost covers large areas of the northern high latitude. The ongoing climate warming causes large-scale thawing of permafrost and mobilization of old dormant carbon introducing a positive feedback to climate warming. In concert with the retreat of permafrost the Arctic landscape and vegetation changes tremendously. This study attempts to trace permafrost dynamics and corresponding vegetation changes in subarctic East Siberia during the last deglaciation to investigate the timing of thaw and elucidate associated climate feedback processes. A piston core retrieved from the western Sea of Okhotsk was investigated. The Sea of Okhotsk is a marginal located at the western rim of Pacific, which is largely influenced by terrigenous material delivered from the Siberian continent. Terrestrial biomarker investigations and compound-specific radiocarbon analyses were performed to examine sources and pathways of permafrost carbon. Plant specific biomarkers were used to investigate vegetation changes in the Amur catchment area. Riverine input of the Amur River and sea level induced remobilization of shelf deposits are the main sources of terrestrial organic matter in the western Sea of Okhotsk. The transport signal shows a strong connection to Northern hemisphere climate variability most likely caused by the coupling to the East Asian monsoon system. The Heinrich stadial 1 is characterized by stable permafrost conditions and widespread tundra vegetation in the Amur catchment. Nevertheless, compound-specific radiocarbon results show a high proportion of permafrost carbon most likely originating from the northern shelf region. Permafrost thaw in the hinterland initiated around 16 ka. Contemporaneously, tundra vegetation was replaced by wetland vegetation and birch forests. Enhanced input of permafrost carbon was found during the Bølling-Allerød and Preboreal warm phases controlled by high riverine input and rapid sea level changes during MWP 1a and MWP 1b. More stable permafrost conditions prevailed during the Younger Dryas. The Holocene is characterized by a gradual decrease of permafrost carbon export and persistent wetland vegetation. The correlation to atmopsheric records implies a release of methane from expanding wetlands and a contribution of permafrost derived carbon to the atmospheric CO2 reservoir.

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Dummann, W. (2015): Thaw-induced release of carbon from permafrost in Eastern Siberia during the last deglaciation , Master thesis, Universität Bremen.

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