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Coastal Oceanography (Subject) / Jacob (Lesson)
- Estuary classification on freshwater Pritchard: a) Positive: River + precipit. > evaporation = Low sallinity b) negative: River + precipit. < evaporation = high sallinity - even higher than in sea c) neutral: River + precipit. = evaporation =
- classification estuaries by tides a) Micro tidal: < 2m b) Meso tidal : 2-4m c) macrotidal: 4-6m d) hypertidal: >6m
- Classification estuary by geomorphology a-d a) drowned river valleys = formed during last glacial , triangular shaped, ~40m depth , formed by erosion, tidal power and sedimentation b) Fiordes: = u shaped, formed by glaciers pressure, excavation river vallies, 300-400m deep or 800m >>at mouth shallow sill that inhibits circulation c) bar built estuaries = shallow, large area. Submarine sill thru sediment budget related to coastal transport (transprot thru steady ind regime) d) tectonic origin: drowned by movements of faults
- classified by mixing process estuary a) Wind = in shallow estuaries with large area > wind can homogenize stuary and can induce drift currents »»wind is very variable - not good for classification b)River discharge :ratio fresh:saltwater density.. froud number (but i dont understand what it really means...) c) Salt sructures with respect to »tides »river discharge during tidal cycle (saltwedge highly stratified; partially mixed; vertically mixed; inverse; intermitten estuaey
- Estuary classification on mixing - salt structures respect to tides: depend on area of estuary and cross section of mouth. Looking at Reynolds number : ratio intertial force:friction force respect to river discharge during tides: 1) salt wedge estuary (highly stratified R=P): seawater enters as a wedge under river water >friction between leayers leads to breaking of internal waves and mixing 2) higly stratified but R<P : more oceanic inflow leading to mor saline values on the surface closer to the mouth of the estuary 3) partially mixed (slighlty stratified)R = 0.25 of P: stronger tidal effect of tides and water oscillate back and forth so high volume of water »using estuarine richards number: force is mixing between both flows : small Ri than instable 4)vertically mixed R = 0.1 of P: no 2 llayer flow but if wide estuary: coriolis force reuslts in horizontal seperartion of lows (lateral gradient) only when narrow its mixed lateral 5)inverse estuary where R+PP<E = higher evaporation than freshwater inflow thus salinity on all surface »inward movement on surface and downward movement towards ocean on bottom due to sinking of water at inner estuary density) 6) untermitten esturies: completly drie up of river so estuary becomes oceanic basin
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