Water and Ice Dynamics in Cook Inlet

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Water and Ice Dynamics in Cook Inlet

• Mark Johnson, UAF
• Andrey Proshutinsky, WHOI
• Stephen Okkonen, UAF
• Chi Hau Chen, UMass
• MMS(CMI)/CISPRI/CIRCAC

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Project Goals

• Improve MMS Environmental Assessment
• Improve oil spill contingency planning
• Better understanding of Cook Inlet circulation,
• Improving Cook Inlet modeling,
• Validating oil spill trajectory modeling.

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We use a high resolution numerical model,
satellite tracked drifting buoys, and winter time
satellite imagery. Our focus is to use a
validated model and observations to identify the
temporal and spatial variability of the tide
rips.
Thanks to Buzz Rome (CISPRI), Steve Okkonen,
Scott Pegau, Carl Schoch, Bob Foy, the Silver
Salmon Creek Lodge, and others for buoy recovery
and deployment!
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Cook Inlet Tidal Current Schematics
Burbank, 1977 and USDOC, NOAA, NOS, 1990, 1975
Burbank, 1977
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Cook Inlet
Cook Inlet Tidal Current Schematics
Burbank, 1977 and USDOC, NOAA, NOS, 1990, 1975
Burbank, 1977
Burbank, 1977
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• FVCOM numerical model
• Tidal forcing with M2, K1, S2, O1
• Assessment with observations
• Agreement with observations

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• Finite Volume Community Model (FVCOM)
• Horizontal resolution
• 160m along coastline
• 13km along open boundary.
• Bathymetry contours in color

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Fragment of grid showing high resolution
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Modeled M2 principal lunar semidiurnal (12.4 h)
tide. Solid lines are magnitudes (m) and dashed
lines are phases.
M2 residual tidal currents
M2 amplitude and phase.
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Modeled M2 principal lunar semidiurnal (12.4 h)
tide. Solid lines are magnitudes (m) and dashed
lines are phases.
M2 residual tidal currents
M2 amplitude and phase.
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Drift River
Kalgin Island
M2 tidal residual currents, upper Cook Inlet.
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Correlation between observed and computed M2
tidal velocities (cm/s).
Correlation between observed and computed M2
directions (degrees) of major tidal axis.
Data from approximately 60 stations are compared
with the model output. M2 (principal lunar
semi-diurnal) and K1 (luni-solar diurnal) account
for half the tidal amplitude. The other
constituents (S2, O1) give the remainder. M2,
S2, O1 and K1 show good agreement with
observations.
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• Satellite tracked buoys
• Mean flow is south
• Highest kinetic energy mid-channel and west rips

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• Data return
• 45 buoys
• drogued at 7 m (track 510 m)
• GPS for hourly positions
• ARGOS data transmission
• redundant
• checksum error detection
• emailed daily
• velocity from central difference
• two (2) failures
• one damaged by ice
• one manufacture (replaced)

Buoy ID Number
Jan 06
Jan 03
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Raw data passing checksum transmission test
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processed data
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lt----------------------------------------------Tid
al harmonics -------------------------------------
--gt
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Buoys north of of 58N
mean
1 std

• Velocity histograms
• u is east
• v is north
• Umean is west, 2 cm s-1
• Vmean is south, 3-4 cm s-1

2 std
3 std
west
east
south
north
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Kinetic Energy 0.5(u2 v2)0.5 cm2 sec-2
mean
--- gt3std ----------------------
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April 2003 through March 2005
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• SAR imagery
• Front locations evident in wintertime ice
• Evidence of west and central rips

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SAR counts
bathymetry gradient
bathymetry
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Timeline
Contours of KE gt 100 cm2 s-2
24-hour averaged V2 energy of surface currents
from vessel drift at 60 29N
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Conclusions

• rips characterized by strong convergence and
  shear
• rips are oriented along strong bathymetric
  gradients
• highest kinetic energy east of Kalgin Island
• finite volume (3D) and finite element (2D) models
  
• agree with observations
• 3D model is
• computationally efficient.
• irregular grid has 1/10 the grid points of the 2D
  rectangular, 1 km grid.
• simulates a stratified fluid
• Model errors could be reduced with better
• bathymetry, and
• wet/dry mapping in upper Cook Inlet, especially
  Turnagain Arm.
• FVCOM is coded for wetting and drying.
• SAR imagery suggests winter ice co-located with
  rip lines

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Recommendations

• Observations of sea level variability are needed
  for at least one summer month and one winter
  month across Cook Inlet entrance
• Instrument spacing of 10-15 km.
• Wetting and drying mechanisms could improve
  agreement between observations and model. More
  observations are needed.
• Assemble a Cook Inlet T-S climatology

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• Thank you
• Mark Johnson
• 907.474.6933

johnson_at_ims.uaf.edu
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Whitney, 1994
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(Whitney, 1994)
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(Whitney, 1994)
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Tidal map for N2 semidiurnal wave from FVCOM
model. Solid lines depict magnitudes (m) and
dashed lines show phase of wave propagation.
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Residual tidal currents generated by N2 tidal
wave.
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Residual tidal currents generated by M2 tidal
wave.
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Tidal map for S2 semidiurnal wave from FVCOM
model. Solid lines depict magnitudes (m) and
dashed lines show phase of wave propagation. S2
is the principal solar tide with a period of 12
hours.
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Left Correlation between observed and computed
S2 tidal velocities representing major axis of
tidal ellipse (cm/s). Right Correlation between
observed and computed directions (degrees) of
major axis of S2 tidal ellipses.
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Tidal map for K1 diurnal wave from FVCOM
model. Solid lines depict magnitudes (m) and
dashed lines show phase of wave propagation. K1
is the luni-solar diurnal tide with a period of
23.9 hours.
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Left Correlation between observed and computed
K1 tidal velocities representing major axis of
tidal ellipse (cm/s). Right Correlation between
observed and computed directions (degrees) of
major axis of K1 tidal ellipses.
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Tidal map for O1 diurnal wave from FVCOM
model. Solid lines depict magnitudes (m) and
dashed lines show phase of wave propagation. O1
is the principal lunar diurnal tide with a period
of 25.8 hours.
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Left Correlation between observed and computed
O1 tidal velocities representing major axis of
tidal ellipse (cm/s). Right Correlation between
observed and computed directions (degrees) of
major axis of O1 tidal ellipses
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1983
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Tide Rip Schematic
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Observational Data for Model Assessment

• Current meters
• Salinity, temperature, depth profiles
• Tide gauges

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Whitney, 1994
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raw hourly positions
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Trajectory from hourly positions
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Trajectory from hourly positions
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Trajectory from hourly positions
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Runs aground on Amlia Island
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Cook Inlet through Amutka Pass into Bering Sea
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Cook Inlet to Shelikof Strait to Kodiak
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Cook Inlet to Shelikof Strait to Kodiak
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MMS 10th Information Transfer Meeting March
2005 Cook Inlet Water and Ice Dynamics
Burbank, 1977
?
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• April 2003 through March 2005

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Southward flow
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Northward flow