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University of Groningen Aluminium and manganese in the West Atlantic Ocean van Hulten, Marco IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2014 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): van Hulten, M. (2014). Aluminium and manganese in the West Atlantic Ocean: A model study [S.l.]: [S.n.] Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 14-06-2017 Aluminium en Mangaan in de West-Atlantische Oceaan een modelstudie Marco van Hulten Colofon Auteurs- en gebruikersrecht: © 2014 door Marco van Hulten Dit werk is gelicentieerd onder een Creative Commons Naamsvermelding-GelijkDelen 3.0 Unported. Bezoek http://creativecommons.org/licenses/by-sa/3.0/ om een kopie te zien van de licentie of stuur een brief naar Creative Commons, 444 Castro Street, Suite 900, Mountain View, California, 94041, USA. Voorzijde: De afbeelding op de kaft van het boekje is een artistieke doorsnede van West-Atlantische Oceaan langs het pad van de Nederlandse Geotraces-cruises. De concentraties opgelost aluminium zijn gemeten door Dr. Rob Middag; de kleurenschaal is dezelfde als in de respectievelijke figuren in Hoofdstukken 3 en 4. Financiëring en projectnummer: Dit werk is gefinancieerd door de Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), beursnummer 839.08.414, deel van het ZKO-programma (Zee- en Kustonderzoek). Gedrukt door: Ipskamp Drukkers, Enschede (www.ipskampdrukkers.nl) Gezet met LATEX2e ISBN-13 978-90-367-7370-6 paperback ISBN-13 978-90-367-7369-0 e-boek Aluminium and Manganese in the West Atlantic Ocean A model study Proefschrift ter verkrijging van de graad van doctor aan de Rijksuniversiteit Groningen op gezag van de rector magnificus prof. dr. E. Sterken, en volgens besluit van het College voor Promoties. De openbare verdediging zal plaatsvinden op vrijdag 28 november 2014 om 14.30 uur en gevoerd worden door Marco Marinus Peter van Hulten geboren op 23 april 1980 te Elshout Promotores: Prof. dr. ir. H.J.W. de Baar Prof. dr. ir. W. Hazeleger Copromotores: Dr. A. Sterl Dr. A. Tagliabue Beoordelingscommissie: Prof. dr. M. Roy-Barman Prof. dr. A.G.J. Buma Prof. dr. G.J. Reichart v For my beautiful wife Jasmijn vi “Unfortunately, however, many, and for the most part those not directly concerned with modelling activity, see in equations facts rather than ideas.” – Joel W. Hedgpeth (1977) “Nothing is impossible. Not if you can imagine it. That’s what being a scientist is all about.” – Hubert J. Farnsworth (3001) from the Futurama sf animation series Contents Nomenclature xi 1 Introduction 1.1 Rationale . . . . . . . . . . 1.2 Oceans and climate . . . . . 1.2.1 Solubility pump . . . 1.2.2 Biological pump . . 1.2.3 Ocean carbon cycle . 1.3 Nutrients and trace metals . 1.3.1 Silicon . . . . . . . . 1.3.2 Aluminium . . . . . 1.3.3 Manganese . . . . . 1.4 Research questions . . . . . 1.4.1 Aluminium . . . . . 1.4.2 Manganese . . . . . . . . . . . . . . . . . 1 1 1 5 8 9 13 13 14 17 20 20 22 . . . . . . . . . . . 25 25 26 28 32 33 34 36 41 49 52 52 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Methodology 2.1 Philosophical introduction . . . . . . . . 2.1.1 Definition of a model . . . . . . . 2.1.2 Examples of models . . . . . . . 2.1.3 The need for models . . . . . . . 2.2 The model NEMO . . . . . . . . . . . . 2.2.1 Configuration: ORCA2 . . . . . 2.2.2 Dynamical model: OPA . . . . . 2.2.3 Biogeochemical model: PISCES . 2.3 Observational data . . . . . . . . . . . . 2.4 Model-data comparison . . . . . . . . . 2.4.1 Predictive uncertainty and error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii Contents 2.5 2.6 2.4.2 Goodness of fit . . . . . . . . . . . . . . . . Epilogue . . . . . . . . . . . . . . . . . . . . . . . . Appendix: Shipboard methods by Dr. Rob Middag 2.6.1 Sample collection . . . . . . . . . . . . . . . 2.6.2 Analysis of dissolved Al . . . . . . . . . . . 2.6.3 Analysis of dissolved Mn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 57 58 58 58 61 3 Aluminium in an ocean model compared with observations 65 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 3.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 3.2.1 Model description . . . . . . . . . . . . . . . . . . . 70 3.2.2 Observations . . . . . . . . . . . . . . . . . . . . . . 79 3.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 3.3.1 Reference simulation . . . . . . . . . . . . . . . . . . 82 3.3.2 Sensitivity simulations . . . . . . . . . . . . . . . . . 88 3.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 3.4.1 Comparison with Gehlen et al. (2003) . . . . . . . . 97 3.4.2 Advection versus scavenging . . . . . . . . . . . . . . 98 3.4.3 Ocean sediments source . . . . . . . . . . . . . . . . 103 3.4.4 Internal coefficients . . . . . . . . . . . . . . . . . . . 104 3.4.5 Al versus Si in NADW . . . . . . . . . . . . . . . . . 107 3.5 Conclusions and outlook . . . . . . . . . . . . . . . . . . . . 109 3.6 Appendix: Observational data quality . . . . . . . . . . . . 111 4 Circulation, resuspension and incorporation of Al 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 4.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Model description . . . . . . . . . . . . . . . 4.2.2 Observational datasets . . . . . . . . . . . . . 4.2.3 Data-model comparison . . . . . . . . . . . . 4.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Reference simulation . . . . . . . . . . . . . . 4.3.2 Improved dynamics . . . . . . . . . . . . . . . 4.3.3 Sediment resuspension . . . . . . . . . . . . . 4.3.4 Biological incorporation . . . . . . . . . . . . 4.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 General biogeochemistry . . . . . . . . . . . . 4.4.2 Sediment source . . . . . . . . . . . . . . . . 4.4.3 Incorporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 118 125 125 132 133 135 135 138 139 142 145 145 147 149 Contents 4.5 4.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Appendix: Sediment resuspension model . . . . . . . . . . . 153 5 Al as a unique mirror image of the biological cycle? 157 6 Manganese in an ocean general circulation model 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Manganese model . . . . . . . . . . . . . . . . . . . 6.2.2 Simulations . . . . . . . . . . . . . . . . . . . . . . . 6.2.3 Observations . . . . . . . . . . . . . . . . . . . . . . 6.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.1 Reference simulation . . . . . . . . . . . . . . . . . . 6.3.2 Other dust deposition field . . . . . . . . . . . . . . 6.3.3 With biological Mn cycle . . . . . . . . . . . . . . . 6.3.4 Low hydrothermal input and small settling velocity . 6.3.5 Unconstrained settling . . . . . . . . . . . . . . . . . 6.3.6 No aggregation threshold . . . . . . . . . . . . . . . 6.3.7 No oxidation threshold . . . . . . . . . . . . . . . . . 6.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 Manganese sources . . . . . . . . . . . . . . . . . . . 6.4.2 Manganese sinks . . . . . . . . . . . . . . . . . . . . 6.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 167 168 168 177 178 180 180 181 183 185 186 187 188 191 191 194 199 7 Synthesis and recommendations 7.1 This study . . . . . . . . . . . . . 7.1.1 Aluminium . . . . . . . . 7.1.2 Manganese . . . . . . . . 7.2 Recommendations . . . . . . . . 7.2.1 Aluminium . . . . . . . . 7.2.2 Manganese . . . . . . . . 7.2.3 Trace metals and particles 7.2.4 Modelling in general . . . . . . . . . . . 201 201 202 202 203 203 204 205 206 . . . . 207 211 214 214 215 . . . . . . . . . . . . . . . . A Sensitivity analysis of the aluminium A.0 Reference simulation . . . . . . . . . A.1 Dynamics . . . . . . . . . . . . . . . A.1.1 Different dynamics . . . . . . A.1.2 No advection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix x Contents A.2 Dust deposition . . . . . . . . . . . . . . . A.2.1 Other dust deposition field . . . . A.2.2 Solubility of Al . . . . . . . . . . . A.2.3 Water column dissolution . . . . . A.3 Sediment sources . . . . . . . . . . . . . . A.3.1 Shallow margin sediments . . . . . A.3.2 Sediment resuspension . . . . . . . A.3.3 Source from the Arctic Ocean . . . A.4 Scavenging . . . . . . . . . . . . . . . . . A.4.1 Partition coefficient . . . . . . . . A.4.2 First-order rate constant . . . . . . A.4.3 Settling velocity . . . . . . . . . . A.4.4 Scavenging by calcium carbonate . A.5 Biological incorporation . . . . . . . . . . A.5.1 Simple incorporation . . . . . . . . A.5.2 Decreased partition coefficient . . . A.5.3 Decreased first-order rate constant A.5.4 Increased dust dissolution . . . . . A.5.5 Moderated incorporation . . . . . A.5.6 Upper limit of incorporation . . . A.6 Reduced opal dissolution . . . . . . . . . . A.6.1 Inhibition by incorporated Al . . . A.6.2 Inhibition by adsorbed Al . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 217 218 220 221 221 222 227 229 229 230 231 234 236 237 237 238 238 241 241 242 243 245 Bibliography 249 Samenvatting 277 Acknowledgements 285 Biography 289 Index 291 Nomenclature Symbols ,→ ˙ := [Tr] {Tr} A··· A B αTr βTr C··· cin δ D Dl d ∆V ∆zi e γ Γ F··· FT “Also see...”; only used in this Nomenclature; look under “Symbols” for operators, quantities and units; look under “Abbreviations and terminology” for acronyms, initialisms and technical terms Time derivative; ẋ := ∂x/∂t Definition Concentration of a ,→tracer ,→Tr (mol dm−3 ) Activity of a tracer Tr (mol dm−3 ) Diameter of a ,→particle Mathematical notation for ,→Al concentrations (M); subscript denotes phase Horizontal ,→eddy diffusion coefficient (m2 s−1 ) Vertical ,→eddy diffusion coefficient (m2 s−1 ) Dissolution fraction of ,→Tr from deposited ,→dust Dissolution fraction of ,→Tr from sediment source Mathematical notation for ,→C concentrations (M); subscript denotes phase Weight factor for the Al/Si incorporation ratio Excretion fraction of ,→DOC Root Mean Square Deviation Root Mean Square Deviation, vertical distribution homogenised Day Gridbox volume (m3 ) Thickness of ,→model layer i Unit vector Activity coefficient, the factor accounting for mixture effects; {Tr} = γ [Tr] ‘Dynamical operator’; this is the full derivative plus eddy diffusion Mathematical notation for ,→Fe concentrations (M); subscript denotes phase ,→Forcing field of dynamical or biogeochemical tracers at one of the ocean interfaces (amount time−1 per length, area or volume) xii Nomenclature fT f fTr fT1:T2 Φ g gzoo G Gmol I K L log µ µphyt mphyt mi mTr mol Mmol M··· M µM nM O P p p pM r rmax RT1:T2 R rl ρ S S··· Sv T T Factor to convert forcing FT to a concentration change Coriolis parameter (rad s−1 ) Mass fraction of an element Tr Molar ratio T1/T2 of a source term Flux of a tracer into the ocean (amount surface−2 time−1 ) Gravity of the Earth, approximately 9.8 m s−2 Grazing rate (s−1 ) Gravitational constant (G ≈ 6.673 × 10−11 N m2 kg−2 ) Gigamole, 109 mol Flow of a tracer (mol s−1 ) Half-saturation constant; at this concentration the concerning process occurs at half the rate Limitation term for phytoplankton growth Natural logarithm Viscosity (Pa s = kg m−1 s−1 ) Rate of photosynthesis (s−1 ) Phytoplankton mortality rate (s−1 ) Mass of body i (kg) Atomic mass of Tr (g mol−1 ) Mole, about 6.022 · 1023 elementary entities of a substance Megamole, 106 mol Mathematical notation for ,→Mn concentrations (M); subscript denotes phase Molar, mol dm−3 Micromolar, 10−6 M Nanomolar, 10−9 M Measured value of a ,→tracer (Observation) Modelled value of a tracer (Prediction) Pressure (Pa = kg m−1 s−2 ) Classical momentum (kg m s−1 ), p = mv Picomolar, 10−12 M Radius of a ,→particle (m) Maximum Al/Si incorporated into living ,→diatom ,→frustules Reaction stoichiometry between reactants ,→T1 and T2 Distance between two bodies (m) Correlation coefficient, vertically adjusted Density (kg m−3 ) Salinity (‰) Mathematical notation for ,→Si concentrations (M); subscript denotes phase Sverdrup, 106 m3 s−1 Temperature (◦ C) (Chapter 1) True value of a tracer (in practice its reference value) (Section 2.4) Nomenclature T Tmol Tr,T1,T2 U, V , W v VP waggr ws x̄ x Mathematical notation for (the concentration of) an arbitrary tracer Teramole, 1012 mol Any ocean tracer, e.g. Al, Mn, Si, C; only used in this Nomenclature Zonal, meridional and vertical component of the ,→velocity (m s−1 ) ,→Velocity (m s−1 ) Phytoplankton growth rate (M d−1 ) Phytoplankton aggregation rate (M−1 d−1 ) ,→Settling ,→speed (often referred to as ‘velocity’) of ,→particles (m s−1 ); −ws ẑ is the ,→settling ,→velocity Average value of a quantity x Vectorial location, (x, y, z) Abbreviations and terminology 1-D 3-D AABW AAIW ADP adsorption Al Alads Albiog Aldiat Aldiss Alpart aluminosilicate AMOC aphotic zone ATP BATS BEC biogenic Boussinesq approximation C CaCO3 clay One-dimensional Three-dimensional AntArctic Bottom Water AntArctic Intermediate Water Adenosine diphosphate The adhesion of a substance onto a surface of a ,→particle Aluminium, member of the boron group with atomic number 13, 3rd most abundant element in the Earth’s crust ,→Adsorbed ,→Al Incorporated biogenic Al Incorporated diatom Al Dissolved Al: Al3+ , Al OH2+ and ,→colloids with < 0.2 µM ,→Particulate Al: either Alads or Albiog , lithogenic Al not included Lithogenic minerals mostly composed of aluminium, silicon, and oxygen Atlantic Meridional Overturning Circulation The deep ocean where there is no light; includes the ,→disphotic zone in this thesis Adenosine triphosphate Bermuda Atlantic Time-series Study (1988–) Biogeochemical Elemental Cycling (ocean biogeochemistry model; previously: biogeochemistry/ecosystem/circulation) Created by organisms The assumption that density differences are sufficiently small to be neglected, except for ,→ g-dependent terms Elemental carbon Calcium carbonate: calcite and aragonite ,→Aluminosilicates with < 2 µm xiii xiv Nomenclature CLIVAR CO2 conceptual model colloid desorption diagenesis diatom DFS3 DIC disphotic zone DOC DSOW dust ECMWF eddy diffusion eddy viscosity empiricism ERA-40 ERS euphotic zone ENSO Fe Fediss fluid forcing frustule GCM Climate Variability and Predictability (2010–), project of the World Climate Programme Carbon dioxide Composition of concepts to clarify the working of certain phenomena, usually presented as a schematic diagram ,→Particle with 1 nm < < 1 µm; however, in observational oceanography particles with < 0.2 µm are often considered ‘dissolved’ The release of a substance from a surface of a particle The change of sediments after ,→sedimentation Functional type of phytoplankton with a silica frustule Third version of the Drakkar Forcing Set (Brodeau et al. 2010) Dissolved Inorganic Carbon The layer of the ocean below the ,→euphotic zone where there is still some light but not enough for net photosynthesis Dissolved Organic Carbon Denmark Strait Overflow Water Atmospheric ,→particles, mainly coming from desserts; deposited again on land and in the ocean European Centre for Medium Range Weather Forecasting Parameterisation for subgrid advection Parameterisation for subgrid transport and dissipation of energy The view that regards observations and experiments as the main source and test of knowledge ,→ECMWF Re-Analysis of 40 yr (sic), a 45-year re-analysis of the atmosphere and surface conditions from September 1957 to August 2002 European Remote Sensing; refers to the ERS-1 and ERS-2 satellites The surface layer of the ocean that is well-lit, i.e. more than 1% of sunlight penetration El Niño–Southern Oscillation, a 2–7 year internal climate oscillation at the Pacific Ocean Iron, a metal with atomic number 26, 4th most abundant element in the Earth’s crust Dissolved Fe: Fe3+ , ligands and colloids with < 0.2 µm Liquid or gas; in case of geophysical fluids the ocean and atmosphere, respectively An external source of a tracer, typically located at the boundary of the model domain Cell wall made of ,→biogenic ,→silica General Circulation Model, a model of general circulation based on the primitive equations Nomenclature GEOSECS Geotraces HAMOCC HOT hydrothermal vent IMAU INCA instrumentalism IPY isopycnal JGOFS light reactions lithogenic LMDzT LSCE LSG mixed layer Mn Mnads Mndiss Mnox MOC MOW model N NADP+ NADPH NADW Navier-Stokes equations NEMO GEochemical Ocean SECtions Study (1972–1978) Programme aiming to improve our understanding of ocean biogeochemical cycles and large-scale distribution of trace elements and their isotopes in the marine environment (www.geotraces. org) (2006–) HAmburg Model for the Ocean Carbon Cycle Hawaii Ocean Time-series (1988–) A fissure in the Earth’s crust, typically found at spreading regions like the Mid-Atlantic Ridge Institute for Marine and Atmospheric research Utrecht INteraction with Chemistry and Aerosols (atmospheric dust model) The view that a scientific theory is a useful instrument in understanding the world (agnostic about realism) 3rd International Polar Year (2007–2009) A surface of constant density Joint Global Ocean Flux Study (1989–2005) The first of two parts of photosynthesis where light energy is stored in ,→ATP and ,→NADPH Originating from the lithosphere; not ,→biogenic Laboratoire de Météorologie Dynamique (atmospheric model) Laboratoire des Sciences du Climat et l’Environnement Hamburg Large-Scale Geostrophic ,→OGCM Ocean layer where properties are mixed by turbulence; between the air-sea interface and the ,→thermocline Manganese, transition metal with atomic number 25, 12th most abundant element in the Earth’s crust ,→Adsorbed Mn Dissolved Mn: Mn2+ and ,→colloids with < 0.2 µm Oxidised Mn: MnOx or colloids thereof with ≥ 0.2 µm Meridional Overturning Circulation Mediterranean Overflow Water Structure for which at least some sentences of a theory, hypotheses or observations are satisfied; ,→conceptual, ,→numerical model Elemental nitrogen Nicotinamide adenine dinucleotide phosphate Reduced form of ,→NADP+ North Atlantic Deep Water Main equations for the description of the motion of fluids: basically conservation of momentum (based on Newton’s second law) for a viscous flow Nucleus for European Modelling of the Ocean xv xvi Nomenclature numerical model O OGCM OPA opal ORCA ORCA2 OSF P particle Pisces plankter plankton POC POM primary production PS I PS II rationalism RMSD ROS SAAMW SAFe sand scavenging sedimentation settling Mathematical model for which no analytical solution exists and hence is typically solved, by approximation, on a computer Elemental oxygen, a highly reactive non-metal with atomic number 8, 1st most abundant element in the Earth’s crust Ocean General Circulation Model Océan PArallélisé, ocean dynamics component of NEMO Biogenic Si (dead ,→diatoms) Any of five meshes based on the conformal mapping of Madec and Imbard (1996) Model configuration based on the 2◦ resolution ,→ORCA mesh, used in ,→NEMO Overturning Stream Function, measure for the ,→MOC in ,→Sv Phosphorus, a non-metallic essential nutrient with atomic number 15 A localised object, typically larger and heavier than ,→colloids Biogeochemical model developed by ,→LSCE and community, component of ,→NEMO-TOP Single member of ,→plankton: a floater Organisms in the water column that cannot swim but move with the currents Particulate Organic Carbon Particulate Organic Matter The storage of chemical energy in organic compounds by living organisms Photosystem I, a protein complex used in the ,→light-dependent reactions Photosystem II, the first protein complex used in the ,→lightdependent reactions The view that regards reason as the chief source and test of knowledge Root Mean Square Deviation Reactive Oxygen Species, chemically reactive molecules among which oxygen ions and peroxides SubAntArctic Mode Water Sampling and Analysis of Fe (an international standard for sampling and cross-validation) ,→Aluminosilicates with > 63 µm The combination of adsorption onto the solid surface of a particle, followed by ,→settling due to insufficient buoyancy of the ,→particle in seawater The last step of particle ,→settling where ,→particles in seawater become part of the sediment The process of sinking of heavy particles through the seawater Nomenclature Si silica Sibiog Sidiss Sidiat silt speed SOD structural realism thermocline TOP tracer velocity WOCE Silicon, a metalloid with atomic number 14, 2nd most abundant element in the Earth’s crust Hydrated silicon dioxide: SiO2 · nH2 O Biogenic Si (dead ,→diatoms) Dissolved Si or silicic acid: Si(OH)4 Si incorporated into the ,→frustules of living diatoms ,→Aluminosilicates with 2 µm < < 63 µm The magnitude of the ,→velocity, ||v||; in the context of sinking of particles through the water column usually named the ,→settling velocity ,→ ws SuperOxide Dismutase The view that regards only structures or relationships as real (as opposed to concrete objects) Layer with a large vertical temperature gradient; between upper ,→mixed layer and deep ocean Tracer in the Ocean Paradigm, biogeochemistry and transport components of NEMO Any property of seawater, e.g. temperature, salinity, iron concentration The rate of change of the position, denoted by the vector v (m s−1 ) World Ocean Circulation Experiment (1990–2002) xvii xviii Nomenclature