Characterizing thermo-erosional landforms in Siberian ice-rich permafrost. Morphometric investigations in the Lena Delta using high-resolution satellite imagery and digital elevation models

• Main Author: Stettner, Samuel / SS
• Format: Thesis
• Language: unknown
• Published: 2015
• Subjects: Arctic; Laptev Sea; Ice; laptev; lena delta; permafrost; Thermokarst; Tundra
• Online Access: https://epic.awi.de/id/eprint/36929/; https://epic.awi.de/id/eprint/36929/1/Master_thesis_Stettner_November2014.pdf; https://hdl.handle.net/10013/epic.45183; https://hdl.handle.net/10013/epic.45183.d001

Rapid warming of the Arctic promotes widespread degradation of permafrost and affects the stability of arctic ecosystems. Thermokarst and thermal erosion are two major processes of permafrost degradation. The spatial extent of thermo-erosional processes and related landforms (e.g. gullies and valleys) and their impact on the widespread degradation of permafrost remains not well quantified. Addressing this research gap, this study is using a combination of field data, high-resolution satellite data and photogrammetically derived digital elevation models (DEMs) to conduct a detailed inventory and spatial analysis of thermo-erosional landforms in order to understand their dynamics as well as their relevance for permafrost degradation. The study area in the central Lena Delta is mainly composed of ice- and organic-rich and syngenetically frozen deposits of Late Pleistocene age called Ice Complex. Besides polygonal tundra, thermokarst lakes, wide thermokarst depressions and undisturbed Ice Complex surfaces the study area features a broad variety of thermo-erosional valleys. During an expedition in summer 2013 RTK GPS measurements of 11 ground control points and 28 transversal and 4 longitudinal profiles were conducted in three key sites. Geometric data fusion of GeoEye-1, RapidEye and ALOS PRISM datasets was performed and several high-resolution DEMs were generated. The DEMs were evaluated for absolute height and slope against the field dataset and the thermo-erosional stream network was mapped and morphometric analysis of the identified features was performed. The highest DEM accuracy was achieved when using a combination of six stereopairs from the years 2006 and 2009. The DEM derived transversal and longitudinal profiles reflect the actual shape and morphometry of the valleys. The identified stream network shows levels of high organization within thermokarst depressions and is poorly developed on the Ice Complex surface. The stream orientation tends to follow the height gradient of the study area towards north¬west, while streams outside of thermokarst depression show two main directions that could reflect the polygonal network in the ground. Accompanying permafrost warming thermokarst and thermo-erosional activity will further promote permafrost degradation. In this context thermo-erosional stream networks will expand within the Ice Complex and act as a major agent for the transport of remobilized fossil organic carbon to the Laptev Sea system.