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Difference in soil parameters between disturbed and undisturbed permafrost soil in Northwest Territories, Canada A thesis presented for the degree of Bachelor of Science at Institute of Environmental Science and Geography University of Potsdam Germany Frieder Tautz Pr¨asidentenstr. 73 16816 Neuruppin Matrikel-Nr.: 780602 [email protected] Potsdam, October 12, 2020 1st supervisor Prof. Dr. Guido Grosse Alfred-Wegener-Institut, Polar- und Meeresforschung Telegrafenberg A45-N, 14473 Potsdam 2nd supervisor Prof. Dr. Julia Boike Alfred-Wegener-Institut, Polar- und Meeresforschung Telegrafenberg A6, 14473 Potsdam Contents List of Figures iv List of Tablesv Acronyms vi 1 Introduction1 1.1 Scientific background........................2 1.1.1 Permafrost distribution and properties..........2 1.1.2 Permafrost carbon climate feedback............3 1.1.3 Thermokarst.........................5 1.1.4 Soil Properties.......................8 1.2 Site description........................... 10 1.3 Disturbance categories....................... 12 2 Methods 14 2.1 Sample extraction in-situ...................... 14 2.2 Acitve layer and permafrost subsampling............. 16 2.3 Laboratory Analyses........................ 18 2.3.1 Biochemistry........................ 18 2.3.2 Grain size analysis..................... 19 2.3.3 Ice content.......................... 21 2.3.4 Soil Organic Carbon Content............... 22 2.3.5 Radiocarbon dating..................... 22 2.4 Statistical approach......................... 23 3 Results 25 3.1 General properties......................... 25 3.2 Biochemistry in active layer and permafrost........... 28 3.3 Grain size distribution....................... 28 3.4 Disturbance categories....................... 29 ii 4 Discussion 33 4.1 General Properties......................... 34 4.2 Biochemistry in active layer and permafrost........... 35 4.3 Grain size distribution....................... 37 4.4 Disturbance categories....................... 37 4.5 Limitations and errors....................... 39 5 Conclusion 41 6 Acknowledgment 42 7 Eidesstattliche Erkl¨arung 43 8 Appendix 55 iii List of Figures 1 Permafrost carbon cycle (Schuur et al. 2015)...........4 2 Schematic of retrogressive thaw slumps (Lantuit and Pollard 2005).................................7 3 Schematic of a non-sorted soil profile (Margesin 2009)......9 4 Physiographic subdivision and overview map of study sites... 11 5 Examples of sites categorised as disturbed at Lake 6....... 13 6 High vegetation at disturbed sites at Lake 6........... 14 7 Examples of sites defined as undisturbed............. 14 8 First pit after drilling the first core at Lake 1........... 15 9 Coring equipment.......................... 16 10 Sampling setup in-situ....................... 17 11 Cylinder and AL soil samples taken at TVC and Lake 11 re- spectively.............................. 17 12 Core obtained at Lake 1 in cooling chamber, AWI........ 18 13 Subsampling for different analyses in cooling chamber...... 19 14 Setup of Rhizon soil moisture sampling, AWI Potsdam..... 21 15 Cryotic processes visible in soil profiles.............. 25 16 Comparison between AL and permafrost of biochemical values and CN-ratio............................ 29 17 Grain size differentiation over the three depth categories of AL measurements............................ 30 18 ALT measurements of disturbed and undisturbed sites..... 31 19 Difference between disturbed and undisturbed sites of biochem- ical parameters........................... 32 20 Grain size distribution....................... 33 21 Weight percentage of grains larger than 1 mm not included in the grain size analysis........................ 41 A1 General temperature regime of permafrost (French 2013).... 55 A2 Map of sampling setup at Lake 1 regarding the main data set. 62 A3 Map of sampling setup at Lake 6 regarding the main data set. 62 A4 Map of sampling setup at Lake 11 regarding the main data set. 63 iv A5 Map of sampling setup at TVC and 1sub3 regarding the main data set............................... 63 A6 Map of sampling setup at Lake 12 regarding the main data set. 64 A7 Map of sampling setup at Lake 1 regarding the extended data set with ALT measurements.................... 64 A8 Map of sampling setup at Lake 6 regarding the extended data set with ALT measurements.................... 65 A9 Map of sampling setup at Lake 11 regarding the extended data set with ALT measurements.................... 65 A10 Map of sampling setup at Lake 12 regarding the extended data set with ALT measurements.................... 66 A11 Map of sampling setup of vegetation sites regarding the ex- tended data set with ALT measurements............. 66 List of Tables 1 Rate of mineralisation in regard to TOC/TN-ratio (Walthert et al. 2004).............................5 2 Radiocarbon age at different sites................. 26 3 Summary of additional measurements - gravimetric and volu- metric ice content, wet and dry bulk densities.......... 27 4 SOCC values at each sample site................. 32 A1 Biochemical parameters of permafrost core and active layer sam- ples.................................. 55 A1 Grain size distribution....................... 57 A1 Excluded grain fraction >1mm.................. 59 A1 Extended data set with ALT measurements........... 60 v Acronyms CH3COOH Acetic acid is a colourless organic acid with the formular CH3COOH. CH4 Methane is an organic gas with the formula CH4. It is utilised as a fuel and forms naturally below ground and under the seafloor by biological and geological processes. In the atmo- sphere, it plays an important role as a Greenhouse Gas. CO2 Carbon dioxide is a colourless gas with the formula CO2, nat- urally occurring in the atmosphere and hydrosphere. It plays a major role as a Greenhouse Gas in the atmosphere where it stores thermal energy and enhances global warming. H2O2 Hydrogen peroxide is a chemical compound used as an oxidiser, bleaching agent and antiseptic. N2O Nitrous oxide, also known as laughing gas, is a chemical molecule with the formula N2O. It is commonly used as an anaesthetic in health system. In the atmosphere, it acts as a Greenhouse Gas 12C The carbon-12 isotope is the most abundant isotope of carbon and makes roughly 98% of the carbon on earth. Its amount in organics is used to determine its age with the Radiocarbon dating method. 13C The carbon-13 isotope is one of the three carbon isotope, is quite stable and makes roughly 1 % of the naturally occurring carbon on earth. 14C The carbon-14 isotope is quite unstable and the rarest of all three carbon isotopes. Its occurrence and decay in organic ma- terials is the basis of the Radiocarbon dating method utilised to determine the age of organics. 14N The nitrogen-14 isotope is the major isotope of nitrogen. m3 1 cubic metre = 1m ∗ 1m ∗ 1m. °C Degree Celsius is a common unit to describe temperature. Zero degree celsius are 32 Fahreneinheit or 273,15 Kelvin. 14C Radiocarbon dating is method utilising the decay of the 14C isotope to determine the age of organic materials for example in soils. a years AL The Active layer is the top soil layer in permafrost areas. It freezes in winter and thaws in summer due to seasonal changes. ALT The Active Layer Thickness is the average annual thaw depth of the acitve layer. AMS The Accelerator Mass Spectrometer is a sensitive device mea- suring the amount and type of isotopes in a probe. Its major use is to determine Radiocarbon date by measuring the amount of the according isotopes. vi AWI Alfred-Wegener-Institut, Helmholtz-Zentrum for Polar and Marine Research C Carbon is a chemical element and the main component of all organics on earth. C/N ratio The Total Organic Carbon to Total Nitrogen ration describes the proportion between those two soil components and is of- ten utilised to indicate the rate of mineralisation in the soil (Walthert et al. 2004). cal. a BP Calibrated radiocarbon years before present refer to the cor- rected age calculation of organic material with the Radiocarbon dating method. Due to different concentrations in the past, the age calculations requires adjustment according to the historic isotope concentrations in the atmosphere. cm 1 centimetre = 1 ∗ 10{2 m DZAA The Depth of Zero Annual Amplitude describes the depth in permafrost soils where there is no annual fluctuations by sea- sonal changes (<0.1 degree celsius (°C)). It is utilised to deter- mine long-term changes of the permafrost temperature. g Gram is the SI-unit for weight. GHG Greenhouse Gases are radioactive gases in the thermal infrared spectrum rising global temperatures with rising concentrations in the atmosphere. This process is termed Greenhouse Effect. GSD The Grain Size Distribution describes the size and relative amount of grains in a probe by mass or volume. It determines the soil class, the soils composition and movement of water. ka Thousand years kg 1 kilogram = 10 g kg/m² kilograms per square metre km 1 kilometre = 1000 m km2 1 square kilometre = 1km ∗ 1km m metre (SI-unit of length) m2 1 square metre = 1m ∗ 1m m/a metre per year mg 1 Milligram = 10{3 metre mineralisation Mineralisation is the process of complete decomposition of or- ganic material to inorganic components - mainly by microor- ganisms activity. It releases primarily photosynthetically se- questered carbon as carbon dioxide as well as other components of the cycle of matter such as nitrogen, phosphor or sulphur. ml 1 millilitre = 10{3 litre. mm 1 Millimetre = 10{3 metre N Nitrogen is a chemical element with the formula N. In soils it
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