Carbon storage, Carbon degradation and sediment transport mechanisms in a changing coastal thermokarst landscape - Case study for a land - near shore transect in the Teshekpuk Lake Region, Alaska, USA

• Main Author: Giest, Frieda
• Other Authors: Strauss, Jens, Grosse, Guido
• Format: Thesis
• Language: unknown
• Published: 2023
• Subjects: Climate change; permafrost; Thermokarst; Alaska
• Online Access: https://epic.awi.de/id/eprint/58908/; https://epic.awi.de/id/eprint/58908/1/Master-Thesis_Giest.pdf; https://hdl.handle.net/10013/epic.c4585654-5e3a-4ea2-97bc-41d894aeff8a

One impact of climate change is the rapid warming of the Arctic, resulting in the thawing of permafrost and associated processes like thermokarst. This leads to the development of thermokarst features, like thermokarst lakes, thermokarst lagoons, and drained thermokarst lake basins. Since permafrost is one of the largest climate sensitive carbon reservoirs of the world, its thaw can possibly lead to the release of substantial amounts of greenhouse gases, thus further exacerbating climate warming. To predict future impacts of permafrost thaw it is of interest to understand how the characteristics of the soils change with a changing permafrost landscape. The aim of this master thesis is the comparison of different landscape features in a dynamic coastal thermokarst landscape, focusing on three main objectives: (1) the quantification and characterization of organic carbon, (2) the sedimentological and depositional characterization, and (3) the quantification of the mercury content in the profiles. The analysis involves six cores, ranging from 12 to 219 cm in length, from six different landscape units within a land-sea transect in Alaska. A multi-proxy approach, including a hydrochemical, a geochronological, a sedimentological, a biogeochemical, and a bio-marker analysis was used to analyse the samples in the laboratory. The results show variations in the total organic carbon (TOC) content within the profiles and across the different landforms. The highest TOC contents were measured in the sediments of the drained thermokarst lake basin and the thermokarst lake. Sites influenced by saltwater have significantly lower TOC contents than the sites not influenced by saltwater, with the semi-drained lagoon and the marine deposits showing the lowest TOC contents. The biomarker analysis indicates a higher level of organic matter degradation in saltwater influenced soil profiles and fresh undegraded organic matter in the thermokarst lake and drained thermokarst lake basin deposits. Moreover, it shows a varying degree of ...