Call number:
AWI G3-19-92383
Description / Table of Contents:
In ice-rich permafrost regions, changes in the permafrost thermal regime cause surface disturbances. These changes are amplified by the increase in air temperatures recorded in the Arctic in the past decades. Thermokarst is a process that leads to surface subsidence and formation of characteristic landforms following thawing of ice-rich permafrost or melting of massive ice. Thermokarst is widespread on hillslopes and the number of associated landforms is increasing in the Arctic. Through this process large amounts of material are eroded and transported to the sea or accumulate along hillslopes. While hillslope thermokarst modifies terrestrial and aquatic ecosystems, there is limited understanding of its environmental impact at a regional scale. In this thesis we quantify the environmental impacts of hillslope thermokarst on the valley and nearshore ecosystems along the Yukon Coast, Canada. Using supervised machine learning, we identified geomorphic factors that favour the development of coastal retrogressive thaw slump (RTS), one of the most dynamic hillslope thermokarst landform. Coastal geomorphology and ground ice type and content play a major role in RTS occurrence. Using aerial photographs and satellite imagery, we traced the evolution of RTSs between 1952 and 2011. During this time, the number and areal coverage of RTSs increased by 73%. RTSs eroded and partly released to the nearshore zone organic carbon contained in millions of cubic meters of material. Our results show that 56% of the RTSs identified along the coast in 2011 have eroded 16.6 × 10^6 m3 of material; a large part (45%) was transported alongshore due to coastal processes. Moreover, we show that RTSs are a major contributor to the carbon budget in the nearshore ecosystem: 17% of the coastal RTSs identified in 2011 contributed annually up to 0.6% of the organic carbon released by coastal retreat along the Yukon Coast. To assess the impact of hillslope thermokarst on the terrestrial ecosystem, we measured the spatial distribution of soil organic carbon (SOC) and total nitrogen (TN) along hillslopes in three Arctic valleys. We highlight the high spatial variability in the distribution of SOC and TN in the valleys. This distribution is caused by complex soil processes occurring along the hillslopes. Hillslope thermokarst impacts the degradation of organic matter and affects the storage of SOC and TN.
Type of Medium:
Dissertations
Pages:
xvii, 103 Seiten
,
Illustrationen
URL:
https://doi.org/10.25932/publishup-42186
Language:
English
Note:
Dissertation, Universität Potsdam, 2018
,
Contents
Acknowledgements
Abstract (English/Deutsch/Français)
List of figures
List of tables
1 Introduction
1.1 Scientic background
1.1.1 The Arctic coast, permafrost and climate change
1.1.2 Organic carbon in permafrost soils
1.1.3 Hillslope thermokarst processes
1.2 Aims
1.3 Study region
1.4 Methods
1.4.1 Mapping
1.4.2 Spline interpolation and volumes estimations
1.4.3 Fieldwork
1.4.4 Geochemical analyses
1.4.5 Statistical analyses
1.5 Thesis outline
1.6 Authors’ contributions
2 Synthesis
2.1 Retrogressive thaw slumps are widely spread in ice-rich permafrost areas
2.2 Retrogressive thaw slumps contribute signicantly to the nearshore or-ganic carbon
2.3 Thermokarst impacts the distribution of soil organic carbon along hill-slopes
2.4 Outlook .
3 Terrain Controls on the Occurrence of Coastal RTSs
3.1 Abstract
3.2 Introduction
3.3 Study area
3.4 Methods
3.4.1 Mapping of retrogressive thaw slumps and landform classication
3.4.2 Environmental variables
3.4.3 Univariate regression trees
3.5 Results
3.5.1 Characteristics of retrogressive thaw slumps
3.5.2 Density and areal coverage of retrogressive thaw slumps
3.6 Discussion
3.6.1 Characteristics and distribution of retrogressive thaw slumps
3.6.2 Terrain factors explaining retrogressive thaw slump occurrence
3.6.3 Coastal Processes
3.7 Conclusion
4 RTSs release sediments and organic carbon into the Arctic Ocean
4.1 Abstract
4.2 Introduction
4.3 Study Area
4.4 Methods
4.4.1 Evolution of retrogressive thaw slumps
4.4.2 Volume Estimations
4.4.3 Estimates of soil and dissolved organic carbon values
4.5 Results
4.5.1 Evolution of retrogressive thaw slumps between 1952 and 2011
4.5.2 Eroded material and estimated amount of mobilized SOC and DOC
4.6 Discussion
4.6.1 Increase in slump activity
4.6.2 Eroded material from retrogressive thaw slumps and organic car-bon uxes
4.6.3 Impact of retrogressive thaw slumps on the coastal ecosystem
4.7 Conclusion
5 Snapshot of carbon and nitrogen distribution in Arctic valleys
5.1 Abstract
5.2 Introduction
5.3 Study Area
5.4 Methods
5.4.1 Spatial analyses
5.4.2 Sampling Scheme
5.4.3 Geochemical analyses
5.4.4 Environmental variables and statistical analyses
5.5 Results
5.5.1 Geomorphology of the valleys
5.5.2 Spatial distribution of carbon and nitrogen
5.5.3 Correlations between soil characteristics and geochemical variables
5.6 Discussion
5.6.1 Variability in soil and geochemical properties in Arctic valleys
5.6.2 Hillslope Processes
5.7 Conclusion
6 Eidessttatliche Erklärung
A Appendix
A.1 Chapter 3
A.2 Chapter 4
A.3 Chapter 5
Bibliography
Location:
AWI Reading room
Branch Library:
AWI Library
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