Microbial signatures and quality assessment of Siberian permafrost organic matter for future biogenic greenhouse gas production

• Main Author: Stapel, Janina Gabriele
• Other Authors: Horsfield, Brian, Mangelsdorf, Kai, Technische Universität Berlin, Wagner, Dirk
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2018
• Subjects: 550 Geowissenschaften; carbon; permafrost; Siberia; biomarker; climate change; Kohlenstoff; Sibirien; Klimawandel; Arctic; Climate change
• Online Access: https://depositonce.tu-berlin.de/handle/11303/7954; https://doi.org/10.14279/depositonce-7116

The Earth´s high latitude regions, where recent warming has been amplified, are of particular concern in the light of future climate change. Annual average temperatures in the Arctic have risen by 0.6 °C per decade over the last 30 years, and this warming trend resulted into the thaw of perennially frozen ground (permafrost), which exposes substantial amounts of previously frozen organic carbon to decomposition by microorganisms. Permafrost is a widespread phenomenon in the Arctic, which constitutes a historical carbon sink of global importance storing twice as much carbon as is currently present in in the atmosphere. Despite having functioned as a carbon sink in the past, it is predicted that significant permafrost thaw will enhance microbial decomposition of the organic carbon and increase microbial greenhouse gas (GHG) emission from the soils into the atmosphere; accelerating warming and promoting further permafrost thaw via a positive feedback. Although permafrost thaw has a strong climate feedback potential, the majority of coupled climate earth system models do not currently include this carbon-climate feedback, and estimates of its size are accompanied by large uncertainties. This doctoral thesis therefore aims to evaluate the future impact of microbial GHG generation from thawing permafrost deposits of different depositional ages for the global carbon cycle. Thus, a combination of detailed bio- and geochemical analyses was conducted on permafrost deposits from two glacial-interglacial cycles (Late Saalian - Eemian and Weichselian - Holocene) on two study sites within the zone of continuous permafrost in north-eastern Siberia to address the research objectives of this doctoral thesis: (1) Characterization of the stored OM of different permafrost units of contrasting ages and regional settings to assess its substrate potential for microbial GHG production and reveal differences between the individual permafrost units. (2) Classification of the distribution of present and past microbial communities in the ...