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Indicators of Volcanism in Ice Cores

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Indicators of Volcanism in Ice Cores Indicators of volcanism in ice cores Master thesis Kasper Holst Lund mjb639 July, 2018 [14] Center for Ice and Climate Niels Bohr Institute University of Copenhagen Supervisors: Paul Travis Vallelonga Helle Astrid Kjær Abstract The work done in this project has been to optimize existing continuous flow analysis 2− + (CFA) techniques used for measurements of sulphate (SO4 ) and acidity (H ). The optimized techniques have been tested on six short firn cores drilled during a 456 km long traverse from the NEEM drilling site to the EGRIP drilling site and on the first 350 metres of the EGRIP ice core. The measured records have been used to determine spatial variability between the cores and to investigate the volcanic signals found in the ice cores. The sulphate technique developed by Röthlisberger et al. (2000) was optimized by exchanging the cation exchange column (CEC) to another type of CEC. This was done to try and reduce the flow problems created by the CEC. The chosen CEC was Bio-Rads Bio-ScaleTM Mini UNOsphere S Cartridge, this had no flow problems in conditions with low dust concentrations while it did show a slight drift with high dust concentrations. The acidity technique developed by Kjær et al. (2016) was optimized by exchange the absorption cell from a 2 cm z-cell to a 1 cm cuvette, this was done to lower the risk of air bubbles getting stuck in the cell. The cuvette handled air bubble a lot better and no problems with air bubbles getting stuck was encountered. The cuvette also improved the response time from 45 seconds to 36 seconds but the sensitivity of the technique was halved due to the lower path length. The sulphate technique was tested on three of the traverse cores but failed to produce any data due to a too high detection limit. The high detection limit is suspected to be due to old chemistry and parts in the setup. No other sulphate measurements were carried out. The acidity and conductivity measurements of the six traverse cores was able to clearly determine volcanic eruption across all of the core but only some of the eruptions showed up in multiple cores. The correlations found between the cores were low and no sig- nificant correlations were found in neither acidity or conductivity. Thus the spatial variation between the cores were quite high even in the big volcanic events. The low correlations are suspected to be due to post depositional effects and to errors in the dating of the cores. The acidity and conductivity measurements of the EastGRIP core also clearly deter- mined big events such as volcanic eruptions and wildfires. A comparison with the NEGIS core drilled very close to the EastGRIP core showed comparable peaks for most of the large events seen while the smaller features had quite some variation most likely due to post depositional effect and errors in the depth assignment. Two conductivity records were measured during the EastGRIP campaign a Bern and a Copenhagen record. A comparison shows that the correlation between the two records gets lower with time. This is most likely due to contamination from build up of par- ticles in the line going from the Bern to the Copenhagen system. This could lead to problems with aligning the records from the different parts of the system. Acknowledgments I would like to thank my supervisor Paul Vallelonga and unofficial co-supervisor Helle Astrid Kjær for thier advice and expert guidance throughout the work on my thesis. Both of them have offered a great amount of help with practical problems in the lab- oratory, by answering all my questions and by correcting my thesis. I would also like to thank Anders Svensson for taking time between being on field work and going on vacation to correct my thesis. This leads me to thank the entire CFA group for all the great discussions on our Monday meetings and the enjoyable environment during the melting campaigns. Thanks to Sam Black and Patrick Zens for good discussions, being good working part- ners and to Patrick for letting me use some of his work for my thesis. This leads to thanking all the people and institutions being part of the EGRIP melting campaign in Bern. They provided an enjoyable and professional environment in the laboratory and a lot of great discussion. Especially a big thanks to Tobias Erhardt and Camilla Maria Jensen for hosting and planning the campaign in Bern. Lastly I would like to thank the Center for Ice and Climate for having me making me feel as a part of the group immediately. I have enjoyed my stay at the center immensely and hope to meet all of the great people here again. The research leading to these results has received funding from the European Re- search Council under the European Community’s Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement 610055 as part of the ice2ice project. EGRIP is directed and organized by the Center of Ice and Climate at the Niels Bohr Institute. It is supported by funding agencies and institutions in Denmark (A. P. Møller Foundation, University of Copenhagen), USA (US National Science Founda- tion, Office of Polar Programs), Germany (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research), Japan (National Institute of Polar Research and Ar- tic Challenge for Sustainability), Norway (University of Bergen and Bergen Research Foundation), Switzerland (Swiss National Science Foundation), France (French Polar Institute Paul-Emile Victor, Institute for Geosciences and Environmental research) and China (Chinese Academy of Sciences and Beijing Normal University). Contents Acknowledgments i Contents ii List of Figures iv List of Tables v 1 Introduction 1 1.1 Ice cores . .1 1.2 Continuous flow analysis (CFA) . .5 2 Acidity in ice cores 12 2.1 Ionic balance . 12 2.2 Volcanic eruptions and their impact on climate . 12 2.3 Determination of pH . 15 2.3.1 Dielectric profiling . 15 2.3.2 Electrical conductivity measurements . 16 2.4 Continuous determination of acidity using optical dye method . 16 2.5 Continuous determination of sulphate . 18 3 Optimizing the CFA techniques for acidity and sulphate 21 3.1 Continuous detection of acidity . 21 3.1.1 Response time . 23 3.1.2 Sensitivity . 24 3.1.3 Acidity spectrum . 26 3.2 Continuous detection of sulphate . 26 3.2.1 Coasol . 28 3.2.2 Cation exchange column . 29 4 Ice core measurements: Traverse cores 33 4.1 Measurements . 33 4.1.1 Standard calibrations . 36 4.1.2 Spatial variation . 38 4.1.3 Volcanic eruptions . 42 5 Ice core measurements: EastGRIP 45 5.1 Measurements . 45 5.1.1 Standard calibrations . 46 5.1.2 Bern and Copenhagen conductivity comparison . 50 5.1.3 Volcanic eruptions . 53 5.1.4 Comparison with NEGIS shallow core . 58 CONTENTS iii 6 Discussion 61 6.1 Sulphate optimization . 61 6.2 Acidity optimization . 62 6.3 Spatial variability . 65 7 Conclusion 67 References 69 Appendix 74 iii LIST OF FIGURES iv List of Figures 1 Flow of an ice sheet . .2 2 Map of drilling locations . .4 3 CFA schematic . .5 4 Melt head . .7 5 Debubbler . .8 6 Abakus . 10 7 Absorption and Fluorence . 11 8 Climatic impact of volcanic eruptions . 13 9 Schematic of pH setup . 16 10 Indicator dyes . 17 11 Schematic of Röthlisberger SO4 setup . 18 12 Schematic of Bigler SO4 setup . 19 13 Absorption cuvette . 22 14 Example of pH standard series . 23 15 Calibration curves of different absorption cells . 25 16 pH absorption as a function of wavelength . 27 17 Coasol test . 28 18 Test of CECs Ca removal . 30 19 Test of CEC flow . 31 20 Schematic of pH setup in Copenhagen . 33 21 Conductivity measurements from the traverse cores . 34 22 Acidity measurements from the traverse cores . 35 23 Calibration curves from the traverse cores . 37 24 Boxplots of the acidity and conductivity . 38 25 Modelled correlation pattern between the traverse cores . 41 26 Acidity events above 3 standard deviations in the traverse cores . 42 27 Conductivity events above 3 standard deviations in the traverse cores . 43 28 Schematic of pH setup in Bern for EastGRIP melting . 46 29 Conductivity and acidity measurement from the EastGRIP core . 47 30 Calibration curves from EastGRIP . 48 31 Histograms of calibration curves from EastGRIP . 49 32 Conductivity from Bern and Copenhagen system . 51 33 Correlation between the Bern and Copenhagen system . 51 34 Boxplot of the Bern and Copenhagen conductivity . 52 35 Diffusion in the conductivity signal . 53 36 Conductivity and acidity events above 3 standard deviations in the EastGRIP core . 54 37 Wildfire at 63.8 meters depth . 57 38 Wildfire at 89.5 meters depth . 57 39 NEGIS and EastGRIP . 58 40 NEGIS and EastGRIP comparison . 60 iv LIST OF TABLES v 41 Absorption cuvette . 64 List of Tables 1 Traverse cores . .4 2 Climatic impact of volcanic eruptions . 14 3 pH reagent . 17 4 Sulphate reagents . 19 5 Response times of the three different absorption cells . 24 6 Calibration parameters of pH standards with different absorption cells . 26 7 Ca standards with Coasol . 28 8 Bio-Rad cation exchange columns . 29 9 Mean of acidity in traverse cores A4, A5 and A6 . 36 10 Correlation of conductivity in traverse cores . 39 11 Correlation of acidity in traverse cores . 40 12 Acidity events above 3 σ in traverse cores . 44 13 Volcanic eruptions in each traverse core . 45 14 Correlation of conductivity between Bern and Copenhagen . 50 15 Biggest acidity events above 5 σ in the EastGRIP core . 56 16 Comparison of volcanoes in NEGIS and EastGRIP . 59 v 1.
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