| Summary: | The Arctic is warming at a rate twice that of other global ecosystems and changing climate conditions in the Arctic are mobilizing long frozen permafrost stores of organic carbon. In regions of extensive ground ice, thawing permafrost can cause land subsidence, and the creation of thermokarst features. The Peel Plateau, Northwest Territories, Canada has extensive thermokarst features exposing early Holocene age paleo-thaw layers and Pleistocene age glaciogenic material deposited by the Laurentide Ice Sheet. This study aimed to see if unique permafrost thermokarst inputs could be readily observed in streams across six diverse thermokarst features via optical and ultrahigh-resolution mass spectrometry. Samples from within thermokarst slump features, and downstream of thermokarst inputs exhibited higher dissolved organic carbon concentrations and lower aromaticity as evidenced by optical parameters (e.g. declining SUVA254, increasing S275-295) and FT-ICR MS metrics (e.g. lower AImod and nominal oxidation state of carbon) versus upstream of thermokarst inputs. Increases in the relative abundances of assigned heteroatomic molecular formulae (e.g. CHON, CHOS, CHONS) were also greater within and downstream of thermokarst features. The unique molecular formulae present in permafrost thermokarst inputs were determined (n=1,844) and subsequently tracked downstream. These permafrost marker formulae were enriched in aliphatics and H/C as well as heteroatoms and exhibited low aromaticity. A portion of the unique molecular signatures persisted downstream, highlighting the potential to not only assess thermokarst inputs but also to follow these inputs and their fate downstream throughout the aquatic network. A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. March 29, 2023. Carbon, Permafrost, Thermokarst Includes bibliographical references. Robert G. M. Spencer, Professor Directing Thesis; Alyssa Atwood, ...
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