Organic carbon in ice-rich permafrost

• Main Author: Strauß, Jens
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2015
• Subjects: ddc:550; Institut für Umweltwissenschaften und Geographie; Arctic; Ice; permafrost; Thermokarst; Alaska; Siberia
• Online Access: https://publishup.uni-potsdam.de/frontdoor/index/index/docId/7523; https://nbn-resolving.org/urn:nbn:de:kobv:517-opus4-75236; https://doi.org/10.25932/publishup-7523; https://publishup.uni-potsdam.de/files/7523/strauss_diss.pdf

Permafrost, defined as ground that is frozen for at least two consecutive years, is a distinct feature of the terrestrial unglaciated Arctic. It covers approximately one quarter of the land area of the Northern Hemisphere (23,000,000 km²). Arctic landscapes, especially those underlain by permafrost, are threatened by climate warming and may degrade in different ways, including active layer deepening, thermal erosion, and development of rapid thaw features. In Siberian and Alaskan late Pleistocene ice-rich Yedoma permafrost, rapid and deep thaw processes (called thermokarst) can mobilize deep organic carbon (below 3 m depth) by surface subsidence due to loss of ground ice. Increased permafrost thaw could cause a feedback loop of global significance if its stored frozen organic carbon is reintroduced into the active carbon cycle as greenhouse gases, which accelerate warming and inducing more permafrost thaw and carbon release. To assess this concern, the major objective of the thesis was to enhance the understanding of the origin of Yedoma as well as to assess the associated organic carbon pool size and carbon quality (concerning degradability). The key research questions were: - How did Yedoma deposits accumulate? - How much organic carbon is stored in the Yedoma region? - What is the susceptibility of the Yedoma region's carbon for future decomposition? To address these three research questions, an interdisciplinary approach, including detailed field studies and sampling in Siberia and Alaska as well as methods of sedimentology, organic biogeochemistry, remote sensing, statistical analyses, and computational modeling were applied. To provide a panarctic context, this thesis additionally includes results both from a newly compiled northern circumpolar carbon database and from a model assessment of carbon fluxes in a warming Arctic. The Yedoma samples show a homogeneous grain-size composition. All samples were poorly sorted with a multi-modal grain-size distribution, indicating various (re-) transport processes. ...