Annual to Millennial Scale Oxygen Minimum Zone Expansion on the Southern California Margin: Proxies and Drivers by Yi Wang A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Earth and Environmental Sciences) in the University of Michigan 2020 Doctoral Committee: Professor Ingrid L. Hendy, Chair Professor Brian K. Arbic Professor Julia E. Cole Associate Professor Rose M. Cory Associate Professor Gregory Dick Assistant Professor Brian R. Ellis Professor Nathan D. Sheldon Yi Wang [email protected] ORCID iD: 0000-0001-5633-3312 © Yi Wang 2020 Dedication This dissertation is dedicated to my late grandma who genuinely supported me. ii Acknowledgements Firstly, I would like to thank Ingrid for taking me as a student, providing me with an opportunity of studying paleoceanography, being patient in teaching me, and constantly pushing me to deal with new challenges (and deadlines!). Thank you for encouraging me to step out of my comfort zone, developing my own ideas, and bringing them to fruition. I would also like to thank my committee – Brian Arbic, Julie, Rose, Greg, Brian Ellis, and Nathan – for their guidance and all the encouragement during my committee meetings. I especially want to thank Rose and Julie for their help in my postdoc applications and inspiring conversations both on academics and life. I would also like to thank my co-authors: Dario Bilardello, Jen Latimer, Bob Thunell, and Jiang Zhu, who have broadened my knowledge, provided technical support, and read my drafts for many times. My thesis would never be done without many hands that help. Special thanks to Angela Dial who taught me how to run mass spec and be a meticulous analytical chemist. Without her taking care of the mass specs I would never be able to finish running through my analyses in months. I want to thank Tiffany, Allie, and Tim for teaching me how to process bulk sediments and show me how to run Fe speciation. Thanks to two undergrads, Alex and Madeline, who helped me grind and load many, many samples for organic carbon analyses. Everyone in the Hendy, Sheldon, and Smith lab has been supportive as officemates. I want to thank Allie Tessin, Tiffany Napier, Katy Rico, Xiaojing Du, Mark Robbins, Madelyn Cook, Molly Ng, Becca Dzombak, and Bekah Stein for reading my manuscripts and providing suggestions for my presentations. I’ve thrown you with many long drafts and thank you all for giving insightful advice that helped me improve them. Many thanks to my new friends at the University of Michigan for being so supportive during my PhD. Thanks to Youngjae Kim, Phoebe Aron, Jenny Bowen, Molly Ng, Sooyeon Kim, Jackie Wrage, Alice Zhou, Chrissie Nims, Li Guan, Yang Qu, and Yuan Zhang for the encouragement, discussions, and fun. Special thank you to the Chinese community in this department (Xiaofei Pu, Hong (Dora) Shen, Bian Wang, Sha Chen, Guolei Han, Yanhan Si, Meichen Liu, Xue Su, and Chengwei Zhang) who has iii organized many group activities (parties, board games, and room escapes!) and allows me to have some place to complain about life. Last but not the least, I would like to thank my family to whom this thesis is dedicated to, especially my grandma who I missed the last chance of seeing almost five years ago and grandpa who took care of me in my childhood. Thanks to my parents who always support me to chase after what I determined to. Thank you to Yi Niu, my partner, for simply staying with me and listening to me when I feel hopeless during my last year. More importantly, thanks for reading half of my thesis within two days and serving as the proofreading person for me. Acknowledgement is made to the National Science Foundation, the University of Michigan Rackham Graduate School, and the University of Michigan Earth and Environmental Sciences Department for funding that made this work possible. iv Table of Contents Dedication ii Acknowledgements iii List of Tables x List of Figures xi List of Appendices xiv Abstract xv Chapter 1 Introduction 1 1.1 Reduction-oxidation (redox) reactions and proxies 3 1.2 Santa Barbara Basin on the Southern California margin 5 1.3 Sedimentary proxies and analytical methods 8 1.4 Thesis structure 9 1.5 References 11 Chapter 2 Development of a Rapid Elemental Analysis Procedure for High-resolution Paleoceanographic Reconstructions 18 2.1 Introduction 18 2.2 Experimental 21 2.2.1 Reagents, standards, and sample matrix 21 2.2.2 Isotope dilution 21 2.2.3 Sample spiking and digestion 22 2.2.4 Column chemistry 23 2.2.5 Quadrupole ICP-MS 25 2.2.6 High-resolution ICP-MS 25 2.3 Results and Discussions 26 2.3.1 Column calibration 26 v 2.3.2 Sensitivity and sensitivity to blank (S/B) ratios 27 2.3.3 Accuracy and reproducibility 28 2.3.4 Comparison with ALS methodology 33 2.4 Conclusions 37 2.5 References 38 Chapter 3 Diagenesis and Iron Paleo-redox Proxies: New Perspectives from Magnetic and Iron Speciation Analyses in the Santa Barbara Basin 40 3.1 Abstract 40 3.2 Introduction 41 3.3 Background 42 3.3.1 Site description 42 3.3.2 Paleo-redox proxies 43 3.4 Methods 46 3.4.1 Magnetic measurements 47 3.4.2 Iron speciation 48 3.5 Results 50 3.5.1 Magnetic measurements 50 3.5.2 Geochemical Fe speciation 54 3.6 Discussion 57 3.6.1 Iron mineral identification from magnetic measurements 57 3.6.2 Iron mineral preservation in rapidly-accumulated reducing sediments 59 3.6.3 The impact of water-column and porewater redox conditions on Fe speciation 61 3.6.4 Instantaneous depositional events and post-depositional diagenesis — an internal “iron shuttle” process 63 3.6.5 Trace metal enrichments in the Santa Barbara Basin 66 3.7 Conclusions and implications 69 3.8 Acknowledgements 71 3.9 References 71 Chapter 4 Climate and Anthropogenic Controls of Coastal Deoxygenation on Interannual to Centennial Timescales 84 vi 4.1 Abstract 84 4.2 Introduction 84 4.3 Materials and Methods 87 4.4 Sedimentary oxygen reconstruction since the Industrial Revolution 89 4.5 Water column observations and the sedimentary redox record 93 4.6 Interannual dissolved oxygen concentrations and ENSO variability 94 4.7 Conclusions 95 4.8 Acknowledgments 96 4.9 References 96 Chapter 5 Local and Remote Forcing of Denitrification in the Northeast Pacific for the Last 2000 Years 101 5.1 Abstract 101 5.2 Introduction 102 5.3 Background 104 5.4 Methods 107 5.5 Results 108 5.6 Discussions 111 5.6.1 Export productivity proxies and upwelling 111 5.6.2 Santa Barbara Basin δ15N history over the past 2000 years 114 5.6.3 Teleconnections to tropical and high-latitude forcing 116 5.7 Conclusions 121 5.8 Acknowledgments 122 5.9 References 122 Chapter 6 Large Natural Variability of the Southern California Oxygen Minimum Zone Revealed During the Common Era 132 6.1 Abstract 132 6.2 Introduction 133 6.3 Background 136 6.4 Methods 138 6.4.1 Geochemical measurements and enrichment factors 138 6.4.2 Last Millennium Reanalysis (LMR) 139 vii 6.5 Results 140 6.5.1 Geochemical measurements 140 6.5.2 LMR results 142 6.6 Discussions 144 6.6.1 Redox control on sedimentary Ba preservation 144 6.6.2 Common Era variability of Southern California oxygenation in the Holocene context 145 6.6.3 Controlling mechanism of Southern California OMZ 147 6.6.4 Impacts of atmospheric forcing on intermediate water ventilation 151 6.7 Conclusions 153 6.8 Acknowledgements 154 6.9 References 154 Chapter 7 Expansion of the Southern California Oxygen Minimum Zone During the Early- to Mid-holocene Due to Reduced Ventilation of the Northeast Pacific 164 7.1 Abstract 164 7.2 Introduction 165 7.3 Background 167 7.3.1 North Pacific Intermediate Water (NPIW) 168 7.3.2 Equatorial Pacific Intermediate Water (EqPIW) 169 7.4 Methods 170 7.4.1 Age Model 170 7.4.2 Redox-sensitive metal fluxes and enrichment factors 170 7.4.3 Model and experiments 173 7.5 Results 173 7.5.1 Geochemical measurements 173 7.5.2 Reduced MH surface density flux and NPIW ventilation in the model 176 7.6 Discussion 177 7.6.1 Dilution and sedimentation rate effects on trace metal accumulation 177 7.6.2 The Early to Mid-Holocene Southern California Benthic Environment 179 7.6.3 Holocene Northeast Pacific Ocean ventilation variability at intermediate water depths 182 7.6.4 Basin-wide oceanic responses to atmospheric forcing in Holocene 186 viii 7.7 Conclusions 188 7.8 Acknowledgments 190 7.9 References 190 Chapter 8 Conclusions 201 8.1 Summary of results and overall conclusions 201 8.2 Synthesis 204 8.3 Future work 205 8.4 References 208 Appendices 210 ix List of Tables Table 2-1 Monitored isotopes, interferences and element calibration ranges 19 Table 2-2 Sensitivity, sensitivity to blank ratios (S/B), and limit of detection (LoD) 28 Table 2-3 Elemental concentrations measured for MESS-3 30 Table 2-4 Elemental concentrations measured for PACS-2 31 Table 2-5 Elemental concentrations measured for HISS-1 32 Table 2-6 Data comparison between ALS method and the MEAL method 34 Table 3-1 Iron speciation procedure and intended target phases 49 Table 3-2 Magnetic properties for iron minerals (following Hunt et al. (1995)) 50 Table 7-1 Core locations for the Southern California depth transect 167 Table A-1 Comparison of Fedith with Raven et al.