Fate of organic matter mobilized from eroding permafrost coasts

• Main Author: Tanski, George
• Format: Thesis
• Language: unknown
• Published: Universität Potsdam 2018
• Subjects: Arctic; Arctic Ocean; Yukon; Herschel Island; Herschel; Ice; permafrost; Thermokarst
• Online Access: https://epic.awi.de/id/eprint/49131/; https://hdl.handle.net/10013/epic.5df7f8c3-b7a0-4c56-88ef-79b0117716f7

Permafrost, defined as ground that remains frozen for at least two consecutive years, is a prominent feature of polar regions. In the Northern Hemisphere, approximately 23 million km2 of the ground are affected by permafrost. Climatic warming, which has a greater effect on the Arctic than on any other region on Earth, leads to permafrost thaw, caused by gradual deepening of the seasonal unfrozen layer (active layer), thermokarst formation (i.e. land subsidence due to ground ice loss) and thermo-erosion. In the course of thaw, formerly freeze-locked organic carbon (OC) is mobilized and mineralized into greenhouse gases (GHGs), fostering further climate warming – a process known as permafrost carbon feedback. Current climate models focus on GHG release from gradual deepening of the active layer and neglect the OC turnover during lateral transport induced by thermokarst and abrupt thermo-erosion. As such, the accelerated erosion of Arctic permafrost coasts, which make up ~34 % of the global coasts, deliver vast amounts of OC into the Arctic Ocean. However, little is known about the amounts of labile and fast bioavailable dissolved OC (DOC), the impact of thermokarst on mobilized organic matter (OM) characteristics, and the release of GHGs from eroding permafrost coasts. To fill that knowledge gap, the main objectives of the thesis are to investigate (i) how much DOC is mobilized from coastal erosion, (ii) how thermokarst and -erosion alters OM characteristics upon thaw on transit to the ocean, and (iii) how much GHGs are emitted from the nearshore zones of eroding permafrost coasts. Field work and sampling took place along the Yukon coast and on Qikiqtaruk (Herschel Island) in the western Canadian Arctic. An interdisciplinary approach was used to quantify OM (OC and nitrogen) as well as to identify degradation processes. The methods used included sedimentology, geo- and hydrochemistry, remote sensing, statistical analyses, and gas chromatography. The thesis shows that considerable amounts of DOC are released from ...