Title Page
Abstract
Contents
1. General Introduction 16
1.1. Background 16
1.2. Study area 19
1.3. Observations 23
2. Enhanced exchange flow during spring tide in the lower estuary 27
2.1. Introduction 27
2.2. Results 31
2.2.1. Exchange flow during spring and neap tides 31
2.2.2. Horizontal salinity gradients during spring and neap tides 36
2.2.3. Contribution of the horizontal salinity gradient to the exchange flow during spring and neap tides 42
2.3. Discussion 48
2.4. Conclusion 52
3. Fortnightly variability of horizontal salinity gradient and exchange flow in the entire estuary 54
3.1. Introduction 54
3.2. Materials and Methods 58
3.2.1. Model description 58
3.2.2. Comparison of salinity and current between observations and models 63
3.2.3. Decomposition of salt flux 68
3.3. Results and Discussion 71
3.3.1. Periodic propagation of the horizontal salinity gradient 71
3.3.2. Fortnightly variation in exchange flow and its cause 79
3.3.3. Restriction of salt intrusion by vertical mixing 85
3.3.4. Model application to realistic topography in the Sumjin River estuary 89
3.4. Summary and Conclusion 92
4. Effect of river discharge on horizontal salinity gradient and exchange flow during fortnightly tidal cycle 95
4.1. Introduction 95
4.2. Materials and Methods 99
4.2.1. Model description 99
4.3. Results 102
4.3.1. Fortnightly variation of horizontal salinity gradient according to river discharge 102
4.3.2. Exchange flow according to river discharge 107
4.3.3. Physical process of salt flux 110
4.4. Discussion 114
4.4.1. Difference between salt inflow and outflow according to river discharge 114
4.4.2. Advance of salt flux conversion time according to river discharge rate 118
4.4.3. Change of determinant of fortnightly variation of exchange flow 120
4.5. Summary and Conclusion 123
5. Summary and Conclusions 125
References 129
Abstract (in Korean) 138
Table 1.1. River discharge and tidal range during the CTD observations 26
Table 2.2. Variables for the tidal Froude number during spring tide (November 5, 2013) and neap tide (October 30, 2013). 47
Figure 1.1. Study area: (a) Overview map of Korea; (b) Southern coastal area of Korea; (c) Sumjin River estuary study area, including... 22
Figure 2.1. (a)Time series of river discharge (blue line) and surface elevation (green line) and (b)the along-channel velocity profiles.... 33
Figure 2.2. (a)Time series of the depth-normalized along-channel velocity profiles and (b) 36-h low-pass-filtered residual flow... 34
Figure 2.3. Hourly mean velocity profiles (gray lines-1-h mean), tidal mean velocity profiles (black dashed lines-24-h mean), and residual... 35
Figure 2.4. Vertical section of the salinity (g kg-1) along the Sumjin River estuary from stations 1-12 during (a) flood and (b) ebb during...[이미지참조] 39
Figure 2.5. Stratification parameter for the Sumjin River estuary taken during both spring and neap tide. A value above 0.32 indicates a... 40
Figure 2.6. (a) Longitudinal distribution of the depth-averaged salinity during the spring tide (red circles and line) on November 5,... 41
Figure 2.7. Comparison of the velocity profile at the current mooring station between analytical model results (UT: gray lines) and...[이미지참조] 46
Figure 3.1. Idealized model domain information. (a) Idealized estuary model domain and the along-channel variations of (b) depth and (c)... 62
Figure 3.2. Comparisons of salinity among observations, an idealized model, and a realistic model. Vertical sections of the along-channel... 66
Figure 3.3. Comparison of flow rates between observations and the idealized model. (a) Time series of the depth-averaged velocity in... 67
Figure 3.4. (a) Time series of sea-level height at the mouth of the idealized estuary and the N and S stand for neap tide and spring tide,... 76
Figure 3.5. Hovmöller diagrams of the (a) total horizontal salt flux (F), (b) landward salt flux (color shading: steady shear dispersion salt... 77
Figure 3.6. Hovmöller diagram of (a) horizontal salinity gradient along the channel (unit: g kg-1 km-1) and (b) time series of salinity...[이미지참조] 78
Figure 3.7. (a) Hovmöller diagram of the depth-averaged absolute value of the exchange flow and (b) timeseries of the intensity of the... 83
Figure 3.8. Hovmöller diagram of the (a) baroclinic forcing (unit: ㎡ s-2), (b) bottom stress (unit: ㎡ s-2), and (c) nondimensional...[이미지참조] 84
Figure 3.9. (a) Time series of sea-surface height (unit: m) and (b) scatter plot of intrusion length (unit: km) of the isohaline 5 versus... 88
Figure 3.10. (a) Time series of sea-level height at the mouth of the real case and the N and S stand for neap tide and spring tide,... 91
Figure 4.1. (A) Time series of sea-level height at the mouth of the idealized estuary and the N and S stand for neap tide and spring tide,... 105
Figure 4.2. Along channel salinity gradient (unit: km-1) during (a) spring and (b) neap tides based on the river discharge rate. The...[이미지참조] 106
Figure 4.3. Hovmöller diagrams of the intensity of exchange flow (unit: ms-1) during low, mean, and high discharge conditions. S and...[이미지참조] 109
Figure 4.4. Hovmöller diagrams of (a, b, c) advective salt flux (FR), (d, e, f) steady shear dispersion salt flux (FE), and (g, h, i) total salt...[이미지참조] 113
Figure 4.5. Hovmöller diagrams of the (a, b, c) baroclinic forcing (unit: m2 s-2), (d, e, f) bottom stress (unit: m2 s-2), and (g, h, i)... 116
Figure 4.6. Vertical section of along-channel exchange flow (unit: m s-1) during (a, b, c) spring and (d, e, f) neap tide during (a, d) low...[이미지참조] 117