This textbook provides an introduction to turbulent motion occurring naturally in the ocean on scales ranging from millimetres to hundreds of kilometres. It describes turbulence in the mixed boundary layers at the sea surface and seabed, turbulent motion in the density-stratified water between, and the energy sources that support and sustain ocean mixing. Little prior knowledge of physical oceanography is assumed. The text is supported by numerous figures, extensive further reading lists, and more than 50 exercises that are graded in difficulty. Detailed solutions to the exercises are available to instructors online at www.cambridge.org/9780521859486. This textbook is intended for undergraduate courses in physical oceanography, and all students interested in multidisciplinary aspects of how the ocean works, from the shoreline to the deep abyssal plains. It also forms a useful lead-in to the author's more advanced graduate textbook, The Turbulent Ocean (Cambridge University Press, 2005). This textbook is a dynamic introduction to turbulent motion occurring naturally in the ocean for undergraduate courses in physical oceanography, and a useful lead-in to the author's more advanced graduate textbook, The Turbulent Ocean. It is supported by more than 50 exercises, with solutions available to instructors online. It Preface ix Notes on the text xi Acknowledgements xiii Abbreviations xv Standard parameters and symbols xvi Units and their symbols xviii SI prefixes xix Approximate values of commonly used measures xx Turbulence, heat and waves 1(36) Introduction 1(2) Reynolds' experiment 3(2) Joule's experiment 5(3) The surf zone: waves and turbulence 8(5) The nature of turbulent flow 13(5) Stirring + diffusion = mixing 13(2) Entrainment and detrainment 15(3) Shear, convergence and strain 18(1) Ocean stratification and buoyancy 19(6) Density 19(3) Buoyancy, and the buoyancy frequency, N 22(1) The oceanic density profile 23(2) Consequences of stratification 25(12) Internal waves and turbulent motion 25(3) Isopycnal and diapycnal mixing 28(4) Suggested further reading 32(1) Further study 32(1) Problems for Chapter 1 33(4) Measurement of ocean turbulence 37(40) Characteristics of turbulence 37(2) Structure 37(2) Stress and flux 39(1) Dissipation 39(1) Transport by eddies 39(4) Reynolds stress 39(3) Heat and buoyancy flux 42(1) Energetics 43(11) Turbulent dissipation, ?, and isotropy 43(2) The range and observed variation of ? 45(2) The rate of loss of temperature variance, XT 47(1) The Kolmogorov length scale, lK 48(1) The turbulence cascade and the structure of turbulence 49(2) The Taylor hypothesis and the spectrum of turbulent energy 51(3) The terms in the energy balance equation 54(5) The rate of production of turbulent kinetic energy by the mean flow 56(1) The turbulent potential energy 56(3) The rate of dissipation 59(1) Measurement techniques and instruments 59(18) The first measurements of turbulence: spectra 60(1) The air-foil probe: the measurement of ? 60(7) First measurements of Reynolds stress, and the related dissipation per unit area 67(4) Estimates of Reynolds stress and ? using an ADCP 71(2) Suggested further reading 73(1) Further study 74(1) Problems for Chapter 2 75(2) Turbulence in oceanic boundary layers 77(39) Introduction: processes, and types of boundary layers 77(4) Convection in the absence of shear 81(4) Convection below a cooled surface or over a heated seabed 81(2) Buoyant plumes and entrainment 83(2) Stress and no convection; the law of the wall 85(2) Stress and buoyancy flux 87(29) The Monin-Obukov length scale 87(2) Diurnal and seasonal heat cycling of the mixed layer 89(6) Other mixing processes in the upper ocean 95(5) The benthic (or bottom) boundary layer 100(2) Tidal mixing and straining in shallow seas 102(4) Suggested further reading 106(1) Further study 107(3) Problems for Chapter 3 110(6) Turbulence in the ocean pycnocline 116(42) Introduction 116(3) Processes of turbulence generation 116(1) The first observations of turbulence in the thermocline 117(2) Shear-flow instability and the transition to turbulence 119(6) The Richardson number in the ocean 125(4) Further turbulence parameters derived from microstructure measurements 129(6) Estimation of ? 129(2) Estimation of eddy diffusion coefficients 131(2) Rf and the ratio of the eddy coefficients of mass and momentum 133(2) Entrainment into the surface mixed layer 135(1) Observations of mid-water mixing processes 135(4) The rate of diapycnal mixing 139(5) Double diffusive convection 144(14) Suggested further reading 149(1) Further study 150(2) Problems for Chapter 4 152(6) Turbulent dispersion 158(39) Introduction 158(10) The properties of dispersants 158(5) Appropriate measures 163(1) Effects of relative eddy and patch sizes 164(4) The dispersion of particles 168(6) Autocorrelation and integral scales 168(2) Richardson's four-thirds power law 170(1) Dispersion of pairs of particles 171(1) Effects of closed vertical circulations on buoyant particles 171(3) Observations of the dispersion of floats 174(6) Surface floats 174(5) Subsurface floats 179(1) The dispersion of solutes: methods and observations 180(17) Dispersion (or horizontal diffusion) of a solute 180(1) Dye releases in the surface boundary layer 180(2) Tracer releases in the pycnocline 182(5) Natural and anthropogenic tracers 187(2) Suggested further reading 189(1) Further study 190(2) Problems for Chapter 5 192(5) The energetics of ocean mixing 197(28) Introduction 197(2) How much energy is required to mix the abyssal ocean? 199(1) The tides 200(4) The surface or barotropic tides 200(1) The internal or baroclinic tides 201(3) The atmospheric input of energy through the sea surface 204(4) The wind stress 204(1) Surface waves 205(2) Buoyancy flux 207(1) The mean circulation and mesoscale eddies 208(1) Internal waves 209(1) Dissipation produced by bottom stress 210(1) Flow through and around abyssal topography 210(6) Geothermal heat flux 216(1) Discussion 217(8) Suggested further reading 218(1) Further study 219(1) Problems for Chapter 6 220(5) References 225(10) Index 235