Mobilization of terrestrial organic matter from thawing Arctic permafrost regions: Insights from lignin-derived phenols and their compound-specific radiocarbon ages

• Main Author: Cao, Mengli
• Other Authors: Tesi, Tommaso, Mollenhauer, Gesine
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2023
• Subjects: Permafrost; Organic carbon; Arctic; Climate warming; Lignin; 550; 550 Earth sciences and geology; ddc:550; Arctic Ocean; Yukon; Bering Sea; Okhotsk; Climate change; Ice; okhotsk sea; permafrost; Sea ice
• Online Access: https://media.suub.uni-bremen.de/handle/elib/7462; https://doi.org/10.26092/elib/2686; https://nbn-resolving.org/urn:nbn:de:gbv:46-elib74629

Global climate change is expected to have a huge impact on Arctic warming, leading to an increased remobilization of permafrost organic carbon. More than twice as much carbon as in the atmosphere is contained in permafrost soils, and may upon destabilization expose large amounts of organic matter to microbial degradation and release climate-forcing greenhouse gases. As an important link in the land-ocean continuum, rivers are important pathways for permafrost OC remobilization. Arctic ocean sediments are thus receptors of terrestrial OC remobilization for a large part of the circum-Arctic drainage basin and offer an archive to study past terrestrial OC remobilization as during the last deglaciation. This thesis studies terrestrial OC in sub-Arctic ocean sediments to study OC remobilization from permafrost regions across temporal and spatial scales. A detailed study of two sediment cores from the Bering Sea and Okhotsk Sea, allowed the reconstruction of vegetation development, permafrost OC mobilization, and transport pathways of permafrost OC remobilization during the last deglaciation. Vegetation development and permafrost OC remobilization have been investigated by analyses of the mass accumulation rate of terrestrial biomarkers (lignin phenols and lipids). To study the influence of climatic conditions on the stability of inland permafrost soils, the sea surface temperature of the Bering Sea was investigated (TEXL86). For the study of terrestrial OC remobilization from different carbon pools, compound-specific radiocarbon analysis (CSRA) was applied to terrestrial compounds (lignin-derived phenols). A modified method for the purification of lignin-derived phenols was used for CSRA. Downcore records of lignin flux from the Yukon and Amur basins covering the early deglaciation to the Holocene are discussed in the first study. It was found that vegetation change and permafrost remobilization occurred earlier in the Yukon than in the Amur basin. The retreat of sea ice coupled with increased sea surface ...