Modeling and Satellite Observations of TidallyDriven Currents and MudFlats Flooding in Cook Inlet, A

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Modeling and Satellite Observations of
Tidally-Driven Currents and Mud-Flats Flooding in
Cook Inlet, Alaska T. Ezer and L.-Y. Oey
Princeton University (supported by MMS)
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WAD applications Tsunami, Storm surge, large
tides, etc.
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The goal is to build a Wetting And Drying (WAD)
scheme that works with 3D OGCM such as the
Princeton Ocean Model (POM)
Side view
Top view
Method Solve full 3-D PE and impose blocking
conditions based on DH? 1. WETMASK 0
for D ? Hdry,
1 otherwise. 2. Uij0 if (DijDi-1,j)/2 ?
Hdry 3. uijkUij
if WETMASKijWETMASKi-1,j 0
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The WAD scheme has been tested for 1D and 2D
idealized cases such as Tsunami Waves (for
details see Oey, OM, 2005, 2006).
At landfall ? 10 m u 15 m/s
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Testing WAD in 3D
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(No Transcript)
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Strong and variable winds
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Strong seasonal river flows from melting snow
2,4
1
5,6
3
7
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Very large tides
10m
2m
Tidal resonant length scale (M2
P12.42h) L(P/4)(gH)1/2 250 km
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Large tidal mud flats in the upper inlet
Tidal Bores in Turnagain Arm 2m high, 3-5 m/s
prop. speed
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• POM-WAD Model
• Curvilinear grid (0.5-1 km)
• Topography of mud-flat areas
• Temp./Sal. stratification
• Winds from local NOAA stations
• Rivers runoff from USGS
• Tidal forcing in south boundary
• Sensitivity Studies
• with/without WAD
• with/without rivers
• with/without stratification

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The amplification of the tides in the inlet are
simulated quite well
Anchorage
Nikiski
Seldovia
mod
Kodiak Island
obs
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Upper Inlet Processes Mud flats
wetting/drying Tidal bores
Knik Arm
Turnagain Arm
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Surface salinity and tidal flows (1h intervals)
Ebb Begins
Ebb 1 hr
Ebb 3 hrs
Ebb 2hrs
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Ebb 5 hrs
Ebb 4 hrs
Flood Begins
Flood 1 hr
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Flood 2 hrs
Flood 3 hrs
Flood 5 hrs
Flood 4 hrs
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Salinity sections in upper CI at low high tide
A
C
Knik Arm
B
A
Turnagain Arm
B
C
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flood
m/s
Velocity and tide level in Turnagain Arm
ebb
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Effect of WAD on tidal amplitude and phase 20
increase in amplitude, 10 lag in phase
with WAD without WAD
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However, it is difficult to validate the models
wetting and drying capability because of lack of
direct observations over the mud flat regions.
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Knik Arm Flooding
Ebbing Time 2h
Ebbing Time 2h 1sec
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Ice drift speed 1-3 m/s ?
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Satellite data may provide a way to evaluate the
wetting and drying in the model
MODIS data during low tide (Inst. Remote Sensing,
USF)
Model at low tide
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Low tide High
tide
Salty waters from the Gulf of Alaska
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Anchorage
Anchorage
15 km
(a) (b)
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Central Cook Inlet Strong tidal velocities over
narrow channels cause Rip-Tides (drifter
data from Mark Johnson, UAF)
EKE
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Flood brings salty water from the Gulf of Alaska,
ebb brings fresh water from the rivers in the
upper inlet- the fronts created cause rip tides
in the central inlet.
I180
I140
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Vertical Velocity
Sensitivity tests show that river discharge is
essential for the development of the Rip Tides
? With Rivers Discharge

• No Rivers (only weak vertical stratification
  from climatology data)

? Homogeneous Water
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• Summary
• A three-dimensional model with dynamic (movable)
  land-sea boundaries has been developed and tested
  for idealized and realistic conditions.
• Simulations of Cook Inlet (Alaska) demonstrate
  the importance of various forcing mechanisms such
  as tides, winds and rivers and their interaction
  with wetting and drying (WAD).
• More quantitative evaluations against
  observations (local and satellite) are needed.
• Further testing of WAD are planned for
  hurricane-induced storm surge and tsunamis.

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Thank You