GEOCHEMICAL CHARACTERIZATION OF SHALLOW SEDIMENTS FROM THE GROUNDING ZONE OF THE WHILLANS ICE STREAM by Kimberly Anne Roush A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Land Resources and Environmental Sciences MONTANA STATE UNIVERSITY Bozeman, Montana April 2019 ©COPYRIGHT by Kimberly Anne Roush 2019 All Rights Reserved ii ACKNOWLEDGEMENTS This work has been the result of a collaboration including multiple people. To start, I want to thank my advisor, John Priscu, for taking me on, a geologist, as a student, entertaining many days of editing, and reminding me to wear deodorant; Mark Skidmore for his enthusiasm and shared story over many a field season; and John Dore for entertaining my wandering questions with respect to the fascinating field of oceanography. Thank you to Alex Michaud and Tristy Vick-Majors for all that you taught me at the bench, sharing your intrigue for polar science and entertaining my never ending stream of recently coded figures. Thank you to Carrie, Wei, Gus and Amy for their enduring inspiration, support in communicating with R, working with the IC, and creating more organization, structure and logical flow to my presentation abilities. Thank you to my family for seeding my curiosity in science and supporting me in this endeavor. iii TABLE OF CONTENTS 1. AN INTRODUCTION TO THE WHILLANS GROUNDING ZONE ................. 1 Structure of the Thesis ......................................................................................... 3 Hypothesis and Objectives ................................................................................... 4 Significance of My Research ............................................................................... 6 Background: Glacio- and Antarctic Marine Environments ................................. 10 Ice Shelves and Ice Shelf Basal Melt ................................................................. 10 Grounding Zones ......................................................................................... 13 Historic Importance and Significance........................................................... 15 Grounding Line ........................................................................................... 16 Grounding Zone Wedge ............................................................................... 17 Identification of SLW and the WGZ ............................................................ 18 Importance of the Siple Coast ...................................................................... 20 Physical Controls on Marine Sedimentation....................................................... 24 Subglacial Fluvial Inputs ............................................................................ 26 Ross Sea Circulation, Advection and Ross Ice Shelf Cavity ......................... 27 Basal Fallout ................................................................................................ 32 Bioturbation ................................................................................................. 32 Synthesis ........................................................................................................... 33 BIBLIOGRAPHY ............................................................................................. 34 2. SEDIMENT POREWATER GEOCHEMISTRY AT THE GZ .......................... 51 Contribution of Authors and Co-authors ............................................................ 51 Introduction ....................................................................................................... 53 Background ....................................................................................................... 55 Physical Characteristics of the Sediment Core ............................................. 55 Water Isotopes ............................................................................................. 56 Dissolved Ions ............................................................................................. 62 Methods ............................................................................................................ 62 Sample Collection and Core Processing ....................................................... 62 Water Column ............................................................................................. 64 Sediment Porewater Extraction .................................................................... 65 Porosity and Particle Density ....................................................................... 68 Porewater Conductivity and Salinity ............................................................ 69 Grain Size .................................................................................................... 70 Grain Composition ...................................................................................... 70 iv TABLE OF CONTENTS CONTINUED Geochemistry............................................................................................... 71 Water Column........................................................................................ 71 Sediment Porewater ............................................................................... 71 Diffusion................................................................................................ 72 Dropstones ............................................................................................. 73 Isotopes ............................................................................................................. 74 Water Column........................................................................................ 74 Sediment Porewater ............................................................................... 75 Results............................................................................................................... 76 Porosity and Particle Density ....................................................................... 76 Porewater Conductivity and Salinity ............................................................ 77 Grain Size .................................................................................................... 78 Grain Composition ...................................................................................... 78 Geochemistry............................................................................................... 79 Water Column........................................................................................ 79 Sediment Porewater ............................................................................... 83 Diffusion................................................................................................ 84 Dropstones ............................................................................................. 84 Isotopes ....................................................................................................... 86 Water Column........................................................................................ 86 Sediment Porewater ............................................................................... 87 Discussion ......................................................................................................... 90 Porosity and Particle Bulk Density ............................................................... 90 Porewater Salinity and Conductivity ............................................................ 90 Grain Size .................................................................................................... 92 Grain Composition ...................................................................................... 93 Geochemistry............................................................................................... 94 Water Column........................................................................................ 94 Sediment Porewater ............................................................................... 96 Diffusion................................................................................................ 99 Isotopes ....................................................................................................... 99 Water Column........................................................................................ 99 Sediment Porewater ............................................................................. 100 Conclusion ...................................................................................................... 103 BIBLIOGRAPHY ........................................................................................... 104 v TABLE OF CONTENTS CONTINUED 3. SEDIMENT POREWATER ORGANIC MATTER ................................................ 110 Contribution of Authors and Co-authors .......................................................... 110 Introduction ..................................................................................................... 112 Methods .......................................................................................................... 116 Sediment Particulate Organic Carbon and Particulate Organic Nitrogen ..... 116 Porewater Dissolved Organic Carbon and Total Dissolved Nitrogen .......... 117 Results............................................................................................................. 118 Sediment Particulate Organic Carbon and Particulate Organic Nitrogen ..... 118 Porewater Dissolved Organic Carbon and