Volcano-Climate Interactions in the Holocene Claire Louise Cooper Submitted in accordance with the requirements for the degree of Doctor of Philosophy The University of Leeds School of Geography School of Earth and Environment February 2020 i | V o l c a n o - climate interactions in the Holocene ii | V o l c a n o - climate interactions in the Holocene The candidate confirms that the work submitted is his/her/their own, except where work which has formed part of jointly authored publications has been included. The contribution of the candidate and the other authors to this work has been explicitly indicated below. The candidate confirms that appropriate credit has been given within the thesis where reference has been made to the work of others. The following chapters contain jointly authored manuscripts where C.L.C. is the lead author: Chapter 2: Evaluating the relationship between climate change and volcanism. Cooper, C.L., Swindles, G.T., Savov, I.P., Schmidt, A. and Bacon, K.L., 2018. Evaluating the relationship between climate change and volcanism. Earth-Science Reviews, 177, pp.238-247. Contributions: C.L.C. conducted the research on existing literature, wrote the paper, and prepared all Figures. G.T.S. provided data included in Figure 3. G.T.S, I.P.S., A.S., and K.L.B. provided commentary and edits to the manuscript. Chapter 3: Evaluating tephrochronology in the permafrost peatlands of Northern Sweden Cooper, C.L., Swindles, G.T., Watson, E.J., Savov, I.P., Gałka, M., Gallego-Sala, A. and Borken, W., 2019. Evaluating tephrochronology in the permafrost peatlands of northern Sweden. Quaternary Geochronology, 50, pp.16-28. Contributions: C.L.C. conducted tephra extraction and geochemical data analysis, performed assignment of tephra to source eruption, wrote the paper including discussion of preservation factors, and prepared Figures 2, 3, 4, 5, and 6, in addition to editing Figure 1. E.J.W, I.P.S. and G.T.S. performed sample collection, and E.J.W. conducted geochemical analysis on Marooned and Stordalen cores. G.M. and W.B. provided radiocarbon data, and A.G-S. provided 210Pb data. G.T.S. and I.P.S. provided supervision of both C.L.C. and E.J.W. and contributed expertise. All authors reviewed the final manuscript. iii | V o l c a n o - climate interactions in the Holocene Chapter 4: Standard chemical-based tephra extraction methods significantly alter the geochemistry of volcanic glass shards Cooper, C.L., Savov, I.P. and Swindles, G.T., 2019. Standard chemical‐based tephra extraction methods significantly alter the geochemistry of volcanic glass shards. Journal of Quaternary Science, 34, pp.697-707 Contributions: C.L.C. designed the experiment, conducted chemical extractions of tephra and conducted geochemical analysis, performed statistical analysis of results, wrote the paper, and produced all Figures. I.P.S. contributed to the experiment design, and assisted with the interpretation of results. G.T.S. assisted with statistical analysis and provided laboratory training and supervision. G.T.S. and I.P.S. provided commentary and edits to the final manuscript and Figures. Chapter 5: Is there a climatic control on Icelandic volcanism? Cooper, C.L., Savov, I.P., Patton, H., Hubbard, A., Ivanovic, R.F., Carrivick, J.L. and Swindles, G.T., 2019. Is there a climatic control on Icelandic volcanism? Contributions: C.L.C. designed the study, compiled the Holocene database, produced all Figures, and wrote the paper. I.P.S. assisted in the design of the study and provided expertise on volcanic mechanics. H.P. and A.H. contributed the palaeoglacial modelling, with assistance and input from J.L.C. R.F.I. contributed the atmospheric modelling, with input from C.L.C. and G.T.S. G.T.S. provided an early version of the Holocene tephra database. All authors provided commentary and edits to the final manuscript and figures. iv | V o l c a n o - climate interactions in the Holocene This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. The right of Claire Louise Cooper to be identified as Author of this work has been asserted by her in accordance with the Copyright, Designs and Patents Act 1988. © 2020 The University of Leeds and Claire Louise Cooper v | V o l c a n o - climate interactions in the Holocene vi | V o l c a n o - climate interactions in the Holocene Acknowledgements The road to the submission of this thesis has been far from direct, and there are many people I must thank for their unwavering support, and without whom I doubt this point could have been reached. First and foremost I give thanks to my primary supervisor Graeme Swindles, who introduced me to tephrochronology, Thai food, and the uniquely frustrating and rewarding world of academic publication. His optimism, encouragement, and ability to see manuscript potential in dozens upon dozens of tephra-devoid microscope slides were an unending source of inspiration and confidence. Likewise to my co-supervisor, Ivan Savov, whose support and enthusiasm for the volcanic side of things helped to keep me on track, and whose geochemical guidance was invaluable for my laboratory work. Additionally, I received a great deal of help from Chris Hayward at the University of Edinburgh, both in the form of EPMA advice and in suggestions for so-bad- they’re-good sci-fi films to watch while running the probe into the late hours of the night. I am also grateful to Matthew Percival and the histology laboratory team at St James’ University Hospital for their help in unsticking several samples when it became clear that those slides contained the only useful tephra to be found in certain Swedish peat cores. For support outside the university, I extend thanks to the entire Leeds Griffins Quidditch team. Through writing-related stress, slotting tournaments around lab work, and coping with several broken bones (only some of them mine), the joy, friendships, and constant undercurrent of fond exasperation were defining parts of my time at Leeds. For knitting circles where we discussed academic plans, for late night coding advice in Hyde Park, for evenings spent partly writing but mostly watching Doctor Who and Buffy the Vampire Slayer, I am grateful. Thank you also to my family. For listening to my rants, both of excitement and frustration. For giving me advice and usually being right. For letting me know when I’m getting ahead of myself, and loving me anyway. It should go without saying, but this would not have been possible without you. Last but not least, to my D&D group. I’m sorry I killed you all that one time. vii | V o l c a n o - climate interactions in the Holocene viii | V o l c a n o - climate interactions in the Holocene Abstract Efforts to understand the complex interactions between distinct earth systems are a vital part of the future of Earth Science. Recent advances in glaciology, atmospheric sciences, and natural hazard modelling have highlighted how variations in separate components on both a local and global scale can affect adjacent systems. Volcanic hazards have been demonstrated to be susceptible to external hydrological and cryospheric influences. It has previously been hypothesised that regional-scale changes to pressure regimes, such as might occur following rapid deglaciation leading to isostatic uplift, might be sufficient to cause widespread changes in eruption frequency in volcanic areas. This theory is often referred to as the ‘unloading effect’. Icelandic volcanic ash can be found in sites across western mainland Europe and the UK, preserved as tephra layers in terrestrial, lacustrine, and marine sediments. These layers provide temporal and geochemical information on the source eruption, and may also be used as a measure of the frequency of explosive eruptions (the most likely to disperse ash over a wide geographic area). However, as tephrochronology is a relatively new discipline, the methodologies and related applications are still in the process of development. This thesis addresses concerns related to the preservation potential and the impacts of commonly used chemical extraction methods of volcanic tephra. This is achieved through laboratory experimentation, EPMA analysis, and statistical evaluation performed on volcanic glasses of various compositions. Additionally, this thesis presents an updated and expanded database of Holocene and Late Glacial tephra in Europe. The final chapter builds on this database in addition to incorporating palaeo-atmospheric and -glacial modelling to evaluate the potential of the unloading effect in Iceland within the last 12,500 years, finding that, while evidence for this effect occurring within the Holocene does exist, it is likely to be a secondary factor in determining eruption frequency. ix | V o l c a n o - climate interactions in the Holocene x | V o l c a n o - climate interactions in the Holocene Contents Chapter 1: Introduction ............................................................................................ 1 1.1 Preface ...................................................................................................... 1 1.2 Context of research & rationale ................................................................ 1 1.3 Primary research aim ................................................................................ 4 1.4 Objectives.................................................................................................. 4 1.5 Thesis structure ........................................................................................