An Introduction to Ocean Turbulence

S. A. Thorpe0521859484, 9780521859486

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).

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Table of contents :
Cover……Page 1
Half-title……Page 3
Title……Page 5
Copyright……Page 6
Contents……Page 7
Preface……Page 11
Notes on the text……Page 13
Acknowledgements……Page 15
Abbreviations……Page 17
Standard parameters and symbols……Page 18
Units and their symbols……Page 20
SI prefixes……Page 21
Approximate values of commonly used measures……Page 22
1.1 Introduction……Page 27
1.2 Reynolds’ experiment……Page 29
1.3 Joule’s experiment……Page 31
1.4 The surf zone: waves and turbulence……Page 34
1.5.1 Stirring + diffusion = mixing……Page 39
1.5.2 Entrainment and detrainment……Page 41
1.6 Shear, convergence and strain……Page 44
1.7.1 Density……Page 45
1.7.2 Buoyancy, and the buoyancy frequency, N……Page 48
1.7.3 The oceanic density profile……Page 49
1.8.1 Internal waves and turbulent motion……Page 51
1.8.2 Isopycnal and diapycnal mixing……Page 54
Further study……Page 58
Problems for Chapter 1……Page 59
2.1.1 Structure……Page 63
2.2.1 Reynolds stress……Page 65
2.2.2 Heat and buoyancy flux……Page 68
2.3.1 Turbulent dissipation, Epsilon, and isotropy……Page 69
2.3.2 The range and observed variation of Epsilon……Page 71
2.3.3 The rate of loss of temperature variance, χT……Page 73
2.3.4 The Kolmogorov length scale, lK……Page 74
2.3.5 The turbulence cascade and the structure of turbulence……Page 75
2.3.6 The Taylor hypothesis and the spectrum of turbulent energy……Page 77
2.4 The terms in the energy balance equation……Page 80
2.4.2 The turbulent potential energy……Page 82
2.5 Measurement techniques and instruments……Page 85
2.5.2 The air-foil probe: the measurement of Epsilon……Page 86
2.5.3 First measurements of Reynolds stress, and the related dissipation per unit area……Page 93
2.5.4 Estimates of Reynolds stress and ε using an ADCP……Page 97
Suggested further reading……Page 99
Further study……Page 100
Problems for Chapter 2……Page 101
3.1 Introduction: processes, and types of boundary layers……Page 103
3.2.1 Convection below a cooled surface or over a heated seabed……Page 107
3.2.2 Buoyant plumes and entrainment……Page 109
3.3 Stress and no convection; the law of the wall……Page 111
3.4.1 The Monin–Obukov length scale……Page 113
3.4.2 Diurnal and seasonal heat cycling of the mixed layer……Page 115
3.4.3 Other mixing processes in the upper ocean……Page 121
3.4.4 The benthic (or bottom) boundary layer……Page 126
3.4.5 Tidal mixing and straining in shallow seas……Page 128
Suggested further reading……Page 132
Further study……Page 133
Problems for Chapter 3……Page 136
4.1.1 Processes of turbulence generation……Page 142
4.1.2 The first observations of turbulence in the thermocline……Page 143
4.2 Shear-flow instability and the transition to turbulence……Page 145
4.3 The Richardson number in the ocean……Page 151
4.4.1 Estimation of Epsilon……Page 155
4.4.2 Estimation of eddy diffusion coefficients……Page 157
4.4.3 Rf and the ratio of the eddy coefficients of mass and momentum……Page 159
4.6 Observations of mid-water mixing processes……Page 161
4.7 The rate of diapycnal mixing……Page 165
4.8 Double diffusive convection……Page 170
Suggested further reading……Page 175
Further study……Page 176
Problems for Chapter 4……Page 178
5.1.1 The properties of dispersants……Page 184
5.1.2 Appropriate measures……Page 189
5.1.3 Effects of relative eddy and patch sizes……Page 190
5.2.1 Autocorrelation and integral scales……Page 194
5.2.2 Richardson’s four-thirds power law……Page 196
5.2.4 Effects of closed vertical circulations on buoyant particles……Page 197
5.3.1 Surface floats……Page 200
5.3.2 Subsurface floats……Page 205
5.4.2 Dye releases in the surface boundary layer……Page 206
5.4.3 Tracer releases in the pycnocline……Page 208
5.4.4 Natural and anthropogenic tracers……Page 213
Suggested further reading……Page 215
Further study……Page 216
Problems for Chapter 5……Page 218
6.1 Introduction……Page 223
6.2 How much energy is required to mix the abyssal ocean?……Page 225
6.3.1 The surface or barotropic tides……Page 226
6.3.2 The internal or baroclinic tides……Page 227
6.4.1 The wind stress……Page 230
6.4.2 Surface waves……Page 231
6.4.3 Buoyancy flux……Page 233
6.5 The mean circulation and mesoscale eddies……Page 234
6.6 Internal waves……Page 235
6.8 Flow through and around abyssal topography……Page 236
6.9 Geothermal heat flux……Page 242
6.10 Discussion……Page 243
Suggested further reading……Page 244
Further study……Page 245
Problems for Chapter 6……Page 246
References……Page 251
Index……Page 261