The Oceans and Rapid Climate Change

Title Page
......Page 3
Copyright
......Page 4
CONTENTS......Page 5
Preface
......Page 7
Ocean Currents of Change: Introduction......Page 9
REFERENCES......Page 12
Rapidity of Global Climate Change......Page 14
Modes of Climate Change......Page 15
I.A. TIMING.......Page 16
I.b. Possible Causes of the Onset of Northern Hemisphere Glaciation.......Page 17
II.a. Feedback Mechanisms: the Conventional View.......Page 22
II.b. Feedback Mechanisms: Possible New View?......Page 23
III.a. A Switch to Non-linear Global Climate System?......Page 26
IV. a. Heinrich Events and Dansgaard-Oeschger Cycles......Page 27
IV. b. Possible Causes of the Heinrich Events and Dansgaard-Oeschger Cycles......Page 29
IV. c. Bipolar Climate Seesaw and Deep Water Circulation......Page 31
IV. d. Synthesis......Page 33
V.a. The Nature of the Last Glacial-interglacial TransitionLGIT......Page 35
V.b. Possible Causes of Abrupt Climate Oscillations During the LGIT......Page 36
VI. b. Controversy Over the Timing of the Last Interglacial.......Page 38
VI.c. Evidence of Climate Instability During the Eemian......Page 39
Vl.d. Holocene......Page 41
VI. e. Little Ice Age LIA......Page 42
Future Dramatic Decadal Time-scale Climate Transitions?......Page 43
Precession Figure 24......Page 45
REFERENCES......Page 47
The Big Climate Amplifier Ocean Circulation-Sea Ice-Storminess-Dustiness-Albedo......Page 58
REFERENCES......Page 61
INTRODUCTION......Page 62
METHODS......Page 64
Greenland Calcium Concentrations......Page 66
North Atlantic Marine Records......Page 68
DISCUSSION......Page 69
REFERENCES......Page 71
INTRODUCTION......Page 74
PRESENT OCEANOGRAPHY AND BATHYMETRY OF THE NORTH ICELAND SHELF......Page 76
Sediment Accumulation and Mass Accumulation Rates......Page 78
Trends......Page 79
Correlations and Periodicities......Page 81
CONCLUSIONS......Page 83
REFERENCES......Page 84
Changes of Potential Density Gradients in the Northwestern North Atlantic During the Last Climatic Cycle Based on a Multiproxy Approach......Page 87
1. INTRODUCTION......Page 88
2.1. Core Stratigraphy......Page 89
2.2. Sea-surface Estimates of Temperature and Salinity......Page 91
2.3. Reconstruction of Thermohaline Gradients in the Subsurfaceto Mesopelagic Layers......Page 92
3.1. Basic Equations Used......Page 93
3.3. Estimating crO From ̿18 O in Foraminifera! Calcite:the Dinocyst Transfer Function Pathway......Page 94
4. THE LATE HOLOCENE-MODERN SITUATION: VALIDATION OF THE APPROACH......Page 96
5. THE EXTREME SITUATION OF THE LGM......Page 98
7.1. Changes in the Thermohaline Structure of the Water Column......Page 99
7.2. Constraints on the age and Amplitude of Maximum Cooling in the Deep Water Layer......Page 100
8. SUMMARY AND CONCLUSIONS......Page 101
REFERENCES......Page 102
INTRODUCTION......Page 105
Antarctic Bottom Water AABW and Lower Circumpolar Deep Water LCDW......Page 106
REGIONAL SETTING......Page 107
Core and Core-top Material......Page 108
Diatom Analysis......Page 109
Stable Oxygen Isotopes......Page 110
RESULTS AND DISCUSSION......Page 111
Core-Tops......Page 112
Late Quaternary Fluctuations......Page 113
Diatom Production vs Lower LCDW Flow......Page 114
Variations in AABW Source......Page 116
REFERENCES......Page 117
1. INTRODUCTION......Page 121
2. MODEL DESCRIPTION......Page 122
4. PRE-INDUSTRIAL EQUILIBRIUM......Page 123
5. THE GLACIAL CLIMATE......Page 125
6.1. Experimental Setup......Page 128
6.2. Freshwater Input in Pre-industrial Climate......Page 129
6.3. Freshwater Input in Glacial Climate......Page 131
6.4. Sensitivity to FI Duration......Page 132
7.2. The Simulated Transient Response......Page 133
7.3. Implications......Page 134
REFERENCES......Page 135
1. INTRODUCTION......Page 139
2. THE MODEL......Page 140
3. MODEL DIAGNOSTICS OF MOMENTUM FLUXES......Page 141
3.2. LGM Fluxes......Page 143
3.3. Vertical Velocities, Easterly Trades, and the Tropical Thermocline......Page 144
4. DISCUSSION AND CONCLUSIONS......Page 145
REFERENCES......Page 147
INTRODUCTION......Page 149
1. MELTWATER EVENTS AND THC......Page 150
2. SCENARIOS OF MELTWATER EVENTS......Page 153
3. NUMERICAL EXPERIMENTS......Page 155
3.1 Present-day Experiments......Page 156
3.2 LGM Experiments......Page 161
4. DISCUSSION AND CONCLUSIONS......Page 164
REFERENCES......Page 166
INTRODUCTION......Page 170
MODEL DESCRIPTIONS......Page 171
INPUT DATA AND SETUP OF NUMERICAL EXPERIMENTS......Page 173
The Effect of the Mixing Scheme on the Thermohaline Circulation......Page 176
The Effect of the Mixing Scheme on the Sedimentation Pattern......Page 181
The Effect of Climate Variability on Deep-Sea Sedimentation......Page 182
Sensitivity of global sedimentation to high-latitudinal surface density variations......Page 189
SUMMARY AND CONCLUSIONS......Page 193
REFERENCES......Page 195
1. INTRODUCTION......Page 199
2. THE OCEAN MODEL AND THE EXPERIMENTS......Page 201
3.1 The Transient Adjustment Process......Page 203
3.2. Meridional Heat Flux and Overturning Circulation......Page 206
3.3 Spatial Changes......Page 208
3.4 Changes in Near-Bottom Flows and Deep Water Formation......Page 210
4. DISCUSSION AND CONCLUSIONS......Page 212
REFERENCES......Page 214
1. INTRODUCTION.......Page 216
2. NUMERICAL RESULTS.......Page 217
3.1 The Transport and Thickness of the NADW Cell.......Page 218
3.2 The Thickness and Ttransport of the AABW Cell.......Page 221
4. SUMMARY AND CONCLUSIONS.......Page 223
REFERENCES.......Page 225
1. INTRODUCTION......Page 226
2. OCEAN GENERAL CIRCULATION MODEL AND DESIGN OF THE NUMERICAL EXPERIMENTS......Page 229
3.1. The Influence of the Horizontal Diffusion Coefficients......Page 232
8.2. The Influence of the Vertical Diffusion Coefficients......Page 235
3 . 3 . The Impact of Varying the Restoring Time Constant for SST......Page 236
3.4. The Impact of Lowering the Surface Temperature to Ice-Age Conditions......Page 238
REFERENCES......Page 240
1. INTRODUCTION......Page 242
2. THE WATER PLANET MODEL......Page 243
3. THE EFFECTS OF OPENING UP DRAKE PASSAGE......Page 245
4. THE EFFECTS OF WINDS IN DRAKE PASSAGE LATITUDES......Page 250
4.1. The Density Structure of the Ocean and the Wind Strength in the Gap......Page 252
5.1. Drake Passage and Paleoclimate......Page 254
5.2. Multiple Equilibria and Climate Variability......Page 255
5.4. Fully Coupled Models and Models with Intermediate Levels of Coupling......Page 256
REFERENCES......Page 257
1. INTRODUCTION......Page 259
2.1 Model......Page 260
2.2 Experimental Design and Background Climates......Page 261
3. ANALYSIS OF STABILITY OF THE OCEAN THERMOHALINE CIRCULATION FOR DIFFERENT CLIMATE......Page 262
4.1 Dansgaard-Oeschger Events......Page 265
4.2 Heinrich Events and Bond-cycle......Page 267
5. CENTENIAL TIME-SCALE RESPONSE OF THERMOHALINE CIRCULATION TO THE GLOBAL WARMING......Page 269
REFERENCES......Page 271
1. INTRODUCTION......Page 274
2. THERMOHALINE CIRCULATION AND THEIR REPRESENTATION IN MODELS......Page 275
3. THE PALEO-THERMOHALINE CIRCULATION AND ITS CHANGES......Page 276
4. THRESHOLDS IN THE OCEAN ATMOSPHERESYSTEM......Page 278
5.1. Short-term Evolution of the Atlantic THC......Page 280
5.2. Long-term Evolution of the Atlantic THC......Page 281
6. STABILIZING AND DESTABILIZING FEED BACK MECHANISMS......Page 283
7. A POSSIBLE RUNAWAY GREENHOUSE EFFECT?......Page 285
8. CONCLUSIONS......Page 286
REFERENCES......Page 287