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Geochemical Tracers of Arctic Ocean Processes: a Study of Gallium, Barium, and Vanadium

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Geochemical Tracers of Arctic Ocean Processes: a Study of Gallium, Barium, and Vanadium The University of Southern Mississippi The Aquila Digital Community Dissertations Spring 2020 Geochemical Tracers of Arctic Ocean Processes: A Study of Gallium, Barium, and Vanadium Laura M. Whitmore University of Southern Mississippi Follow this and additional works at: https://aquila.usm.edu/dissertations Part of the Biogeochemistry Commons, Environmental Chemistry Commons, Geochemistry Commons, and the Oceanography Commons Recommended Citation Whitmore, Laura M., "Geochemical Tracers of Arctic Ocean Processes: A Study of Gallium, Barium, and Vanadium" (2020). Dissertations. 1780. https://aquila.usm.edu/dissertations/1780 This Dissertation is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Dissertations by an authorized administrator of The Aquila Digital Community. For more information, please contact [email protected]. GEOCHEMICAL TRACERS OF ARCTIC OCEAN PROCESSES: A STUDY OF GALLIUM, BARIUM, AND VANADIUM by Laura M. Whitmore A Dissertation Submitted to the Graduate School, the College of Arts and Sciences and the School of Ocean Science and Engineering at The University of Southern Mississippi in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Approved by: Dr. Alan M. Shiller, Committee Chair Dr. Christopher T. Hayes Dr. Denis A. Wiesenburg Dr. Leila J. Hamdan Dr. Paul D. Quay ____________________ ____________________ ____________________ Dr. Alan M. Shiller Dr. Jerry D. Wiggert Dr. Karen S. Coats Committee Chair Associate Director of Dean of the Graduate School School May 2020 COPYRIGHT BY Laura M. Whitmore 2020 Published by the Graduate School ABSTRACT The Arctic Ocean is linked to the global oceans and climate through its connectivity with the North Atlantic Ocean and the regional thermohaline deep water formation sites. It’s also a region undergoing rapid environmental change. To inform the community of potential changes in geochemical and biogeochemical cycles, this dissertation addresses three dissolved geochemical tracers (gallium, barium, and vanadium) as indicators of Arctic Ocean processes. Gallium is tested as a replacement for nutrient-type tracers in an effort to deconvolve Pacific and Atlantic derived waters in the Arctic Ocean basins. These water masses carry different heat and salt content and can influence sea ice melt, buoyancy, and deep water formation; thus, the accurate assignment and quantification of these waters is critical. It is shown that use of dissolved gallium yields a more realistic separation of these water types than is provided by the nutrient tracers. In contrast to gallium, dissolved barium and vanadium distributions are substantially modified by regional margin processes. Yet, the two elements differ in their behavior on the shelf: shelf processes create a benthic source of barium and a sink for vanadium. More specifically, particle scavenging coupled with reducing shelf sediments appear to remove vanadium from the water column. The source of barium is less clear, but, in part, particulate formation associated with biological activity likely shuttles barium from surface waters to shelf bottom waters where dissolution of the particulate barium is a source. The influences of these processes are observed throughout the upper water column of the western Arctic Ocean and, to some extent, Arctic Ocean deep waters. Furthermore, this work is pertinent to questions related to the net effect of marginal basin shelves on oceanic V & Ba cycling, their isotopic balance, and how ii climate induced changes in shelf biogeochemical cycling will impact geochemical cycling. iii ACKNOWLEDGMENTS Thank you to the members of my committee and my co-authors for their guidance and contributions to the topics presented in this dissertation. Dr. Alan Shiller has my deepest gratitude for his committed mentorship throughout my Ph.D. The members, past and present, of the Shiller and Hayes Labs have been instrumental in this work. Especially Melissa Gilbert for her analytical expertise and time; Dr. Peng Ho for her breadth of trace element knowledge; and Dr. Virginie Sanial for her oceanographic knowledge and curiosity. This research was supported by the National Science Foundation (OCE-1435312). I owe many thanks to the captain and crew of the USCGC Healy (HLY1502) and to the scientific crew and team that has been working hard to understand the results. For their leadership through this effort, thank you to the cruise PIs: Bill Landing, Dave Kadko, and Greg Cutter. Additionally, many members of the School of Ocean Science and Engineering have supported my growth in academia, and they have my gratitude. Thomas Kelly, who has discussed every part of this dissertation with me and has read and reread drafts upon drafts, is the gosh-darned best. He deserves an endless supply of my appreciation. I guess I’ll marry him. iv DEDICATION This work is dedicated to my parents, Elizabeth and Paul Whitmore, who have always encouraged my education. They inspired in me a curiosity, love, and care for nature around which my life has grown. Together they fostered a team of Whitmores in our family that has supported me through this process, from grinning to griping. My siblings, Leanne and Nick, have elevated me with hours of laughter. Mom and Dad, thanks for all the love. v TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii ACKNOWLEDGMENTS ................................................................................................. iv DEDICATION .................................................................................................................... v LIST OF TABLES ............................................................................................................. xi LIST OF ILLUSTRATIONS ............................................................................................ xii LIST OF ABBREVIATIONS ............................................................................................. 1 CHAPTER I - INTRODUCTION ...................................................................................... 4 1.1 References ................................................................................................................. 8 CHAPTER II – GALLIUM: A NEW TRACER OF PACIFIC WATER IN THE ARCTIC OCEAN ............................................................................................................................. 10 2.1 Abstract ................................................................................................................... 10 2.2 Introduction ............................................................................................................. 11 2.3 Methods................................................................................................................... 16 2.3.1 Section Description .......................................................................................... 16 2.3.2 Ancillary Hydrographic Data ........................................................................... 18 18 2.3.3 δ O-H2O Analytical Methods ......................................................................... 19 2.3.4 Ga Sample Collection and Analytical Methods ............................................... 19 2.3.5 Linear Mixing Model ....................................................................................... 21 2.4 Results and Discussion ........................................................................................... 22 vi 2.4.1 Gallium Distribution ........................................................................................ 22 2.4.2 Linear Mixing Model Results .......................................................................... 26 2.4.3 Inventories........................................................................................................ 31 2.4.4 Vertical Advection-Diffusion Model ............................................................... 34 2.5 Conclusions ............................................................................................................. 37 2.6 Acknowledgements ................................................................................................. 38 2.7 References ............................................................................................................... 39 CHAPTER III – ARCTIC OCEAN BARIUM BUDGET REVEALS LARGE MARGIN INPUTS TO THE BASIN ................................................................................................ 44 3.1 Abstract ................................................................................................................... 44 3.2 Introduction ............................................................................................................. 44 3.3 2015 Arctic GEOTRACES Sections ...................................................................... 48 3.3.1 Section Hydrography ....................................................................................... 50 3.4 Methods................................................................................................................... 54 3.4.1 Sample Collection and Analysis ...................................................................... 54 3.4.1.1 Dissolved Barium Concentrations ............................................................ 54 3.4.1.2 Dissolved Ba Isotopes ..............................................................................
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