![Page 1: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/1.jpg)
Tides and the salt balance in a sinuous coastal plain estuary
H. Seim, UNC-CH
J. Blanton, SkIO
Tides
Residual circulation
Salt balance
![Page 2: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/2.jpg)
•Finite Element •Nonlinear•2D (ADCIRC)•Western North Atl.•Crossshelf Amplification•Equatorward phase propagation •Latest phase along GA/FL border
•Shelf response sensitive
NC
SC
FL
GA
Modeled M2 elevation without estuaries – tide experiences two-fold amplitude
increase and notable phase change in SAB
m
(B. Blanton)
![Page 3: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/3.jpg)
In the SAB large sections of the coastline are backed by extensive estuaries
(K. Smith, D. Lynch)
depth (m
)
![Page 4: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/4.jpg)
M2 Solution Elevation Difference
Amplitude Ratio Est sol’n Amp-------------------------- > 1 NoEst sol’n Amp
Phase Diff (in red) Est Phase - NoEst Phase>0
(B. Blanton)
![Page 5: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/5.jpg)
Change in solution associatedwith energy flux into estuaries.
Estuaries must be a sink of energy(high dissipation)
![Page 6: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/6.jpg)
Including estuaries increases dissipation >25%...
Strange result – inclusion of highly dissipative estuaries leads to 10% increase in tidal range.
Log10W/m2
Longitude Latitude
(B. Blanton)
![Page 7: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/7.jpg)
Satilla River 1 m tide2-4 m mean depth50 m3/s avg riverflow0.5-1 m/s tidal currentsPristine, multiple channels in lower estuary5 km MHHW width, 1km MLW width
![Page 8: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/8.jpg)
Bottom topography – not well known (last full survey in 1920s), not maintained
![Page 9: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/9.jpg)
Field program in1999 – mooringsand surveying
Two deployment periods,spring and fall
![Page 10: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/10.jpg)
![Page 11: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/11.jpg)
Rapid survey tracks
![Page 12: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/12.jpg)
Tidal analysis
• Derived tidal constituents (using t-tide) from 2 month-long records at mooring locations
• Compared to shelf observations in Blanton et al. 2004
![Page 13: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/13.jpg)
M2 tide – maximum in estuary…
*
*
shore
shelf
![Page 14: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/14.jpg)
M2 currents – increasing landward, big phase change
shelf
shore
![Page 15: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/15.jpg)
Tide increasingly ‘progressive’ moving inshore
Weirdexception
shelf
shore
![Page 16: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/16.jpg)
Hypersynchonous estuary
• Strongly convergent geometry (Lb<<λ)
• No reflected tidal wave
• Wave speed close to √(gH)
• Phase difference typically like standing wave but sensitive to geometry, friction
![Page 17: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/17.jpg)
Energy flux and dissipation
• Big energy flux at mooring sites (7000-21000 W/m)
• Infer large dissipation rates (0.5-1.5 W/m2)
• Equivalent to 10-4 W/kg, 10,000-100,000 open ocean values.
![Page 18: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/18.jpg)
Roving survey analysis
• Performed least-squares fits to zero, semi-diurnal and quatra-diurnal frequencies
• Q: is there cross-channel structure to the flow?
![Page 19: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/19.jpg)
![Page 20: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/20.jpg)
![Page 21: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/21.jpg)
![Page 22: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/22.jpg)
![Page 23: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/23.jpg)
Depth-scaling accounts for ~25% of variance – rest due to bends andnon-linearities?
![Page 24: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/24.jpg)
Flow around bends in rivers – big influence, but simple
topography, trickier in the estuary
![Page 25: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/25.jpg)
Tidal energy – can be dissipated or transferred to other frequencies…..generate STRONG depth-averaged mean circulation, amazing pattern associated with bends
![Page 26: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/26.jpg)
inland
seaward
Subtidal flow – nearly all moorings show seaward flow – in deep channel
![Page 27: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/27.jpg)
Example axial velocity map
Spr
Np
Landward
Seaward
![Page 28: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/28.jpg)
![Page 29: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/29.jpg)
Salinity regime
SAT 1
SAT 2
![Page 30: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/30.jpg)
Alongchannel salinity field response – rapid adjust to discharge pulses, slow recovery
![Page 31: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/31.jpg)
![Page 32: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/32.jpg)
Salinity response to discharge
![Page 33: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/33.jpg)
![Page 34: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/34.jpg)
Alongchannel salinity
• Obvious maximum gradient, often in region of the bends
• Asymmetric temporal response to discharge changes – fast seaward, slow landward
![Page 35: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/35.jpg)
Mean surface salinity – show strong cross-channel structure
![Page 36: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/36.jpg)
Mean salinity profilesshow x-channel structure extends to depth
![Page 37: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/37.jpg)
Stratification weakerat spring tides butx-channel structurepersists
![Page 38: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/38.jpg)
Axial velocity around Station 4
Spr
NpSpr
Np
![Page 39: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/39.jpg)
![Page 40: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/40.jpg)
1D longitudinal dispersion fit requires salt flux of 0.1 PSU*m/s…
![Page 41: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/41.jpg)
Speculation on lateral exchange in salt balance
Spring
• Exchange system is part of system of tidal eddies
• Flow in deep channels carries salt seaward
• Landward flux is result of tidal asymmetry in favor of flood
• Seaward salt flux is exchanged by landward flow upstream from cross-over flow
Circulation at bendstrap the salinity gradient, slows upstreammovement of salt intrusion
Natural buffer to variationin salinity intrusion?
![Page 42: Tides and the salt balance in a sinuous coastal plain estuary](https://reader035.vdocument.in/reader035/viewer/2022062518/56814b6c550346895db85a18/html5/thumbnails/42.jpg)
Average axial velocity profiles
Ebb > 0
Riv
er v
eloc
it y • Subtracting ur from profile still leaves no evidence for vertical exchange
• Provides strong suggestion for lateral exchange
intertidal