Modeling Puget Sound

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Modeling Puget Sounds Circulation and its
VariabilityOcean 520 SeminarDecember 11, 2002

• Mitsuhiro Kawase
• School of Oceanography, University of Washington

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• A Modeling Partnership for Puget Sound
• Puget Sound Circulation Model Status
• Tidal Currents and Mixing
• Exchange Circulation
• Seasonal Cycle
• Interannual Variability in Puget Sound

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Modeling Efforts in Puget Sound
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A Partnership for Modeling the Marine Environment
of Puget Sound
FY 2002-2007, 4,454,000
University of Washington School of
Oceanography University of Washington College of
Education King County Department of Natural
Resources Ocean Inquiry Project U.S. Naval
Shipyard, Bremerton Washington State Department
of Ecology
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Partnership Objectives

• Develop, maintain and operate a system of
  simulation models of Puget Sounds circulation
  and ecosystem, a data management system for
  oceanographic data and model results, and an
  effective delivery interface for the model
  results and observational data for research,
  education and policy formulation.
• Develop fundamental understanding of the Sounds
  working, and address questions raised by the
  regional community concerning management of the
  Sound and its resources.

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Inlet-Scale Integrated Modeling System for
Sinclair and Dyes Inlet Watershed (Puget Sound
Naval Shipyard, Bremerton)
Watershed Model (HSPF)
Receiving Water Model (CH3D/WASP)
Demonstration of fecal coliform transport in
Sinclair and Dyes Inlets using CH3D-FC
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South Puget Sound Model Nutrient Study
(SPASM) (Washington Department of Ecology)

• Three-dimensional circulation model coupled to a
  water quality/sediment model (EFDC)
• Modeling of circulation, T, S, biologican oxygen
  demand

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Hydrodynamic and Fate and Transport Numerical
Model for the Duwamish River and Elliott
Bay (King County DNR)

• EFDC model
• Circulation, temperature, salinity, sediments,
  contaminant transport (metals, organics)
• For assessing impact of combined sewage outflow
  (CSO) into Duwamish River estuary

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UW-PRISM Puget Sound Circulation Model

• Based on Princeton Ocean Model (POM, Blumberg and
  Mellor, 1987)
• Circulation, temperature, salinity, turbulent
  mixing (aquatic biogeochemistry and sediment in
  the future)
• Fine (360mx540m) and coarse (600mx900m)
  resolution versions
• One-year integration for 2000
• Tidal forcing at external boundaries in Strait of
  Juan de Fuca
• River input from USGS gauge data
• Atmospheric forcing Observations at UW
  Atmospheric Sciences Building (single point
  applied to the whole basin)
• T and S external boundary condition from JEMS
  data set (quasi-monthly sampling of three
  stations along N-S section from San Juan Island
  to Sequim)

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Tidal Currents

• Admiralty Inlet
• Triple Junction
• Tacoma Narrows

Animations by Christian Sarason, OIP
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Strong currents at the sills generate vigorous
turbulent mixing

• High mixing rates in Admiralty Inlet, Tacoma
  Narrows and Hood Canal sill region
• Elevated mixing along boundaries and heads of
  inlets
• Weak mixing in basin interiors

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Exchange Circulation

• Point Edwards
• Possession Sound

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Average Along-channel Flow at Point Edwards, June
28- July 27, 2000
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Average Along-channel Flow in Possession Sound,
November 25 - December 24, 2000
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Seasonal Cycle
Saratoga Passage (WA-DOE SAR 003)
Point Jefferson (KC-DNR KSBP01)
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Temperature and Salinity at 100m, off Point
Jefferson
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2000 Temperature at Point Jefferson, Model-Data
Comparison
Temperature (C)
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2000 Salinity at Point Jefferson, Model-Data
Comparison
Salinity (PSU)
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2000 Temperature in Saratoga Passage, Model -
Data Comparison
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2000 Salinity in Saratoga Passage, Model - Data
Comparison
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Summary Puget Sound Circulation Model Status

• Successes
• Tidal levels and currents
• Exchange circulation in the Main Basin
• Recirculation around Vashon Island
• Seasonal T and S in Whidbey Basin
• Problems
• Too vigorous an exchange circulation in
  Possession Sound
• Failure to capture 2000 spring-summer fresh event
  at Point Jefferson
• Uncertainties
• Boundary currents in Whidbey Basin
• Turbulent mixing, dissipation
• Outside boundary conditions in Strait of Juan de
  Fuca

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Interannual Variability
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Salinity Anomaly, Puget Sound Main Basin at 100m
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R0.6 (36 of variance)
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Salinity and Potential Density in Central Puget
Sound, 1990 - 1998(Blue 100m Red 200m)
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Temperature Anomaly in Puget Sound and Pacific
Decadal Oscillation
R0.57 (33 of variance)
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• How sensitive is the Sounds water masses to
  changes in forcing conditions, e.g. fresh water
  input, oceanographic conditions along the Pacific
  coast?
• Do changes in water mass characteristics imply
  changes in circulation?

Three-dimensional models are costly to run (one
day five hours on a top-end Athlon MP
workstation)
Simple toy model to explore sensitivity of
circulation
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A Simple Box Model of Seasonal and Interannual
Variability in Puget Sound CirculaitonAmanda
Babson, M.S. Thesis 2002

• Twelve-box model based on an efflux-reflux model
  of Cokelet et al. (1990) and the dynamics of a
  simple box model of Georgia Basin - Strait of
  Juan de Fuca by Li et al. (1999)
• Conserves volume and salinity
• Forcing from river discharge and external (SJDF)
  salinity
• Deep inflow proportional to density difference
  between basins (Stommel, 1961)
• Mixing with a stratification-dependent cutoff
• Model calibrated to mean annual
  forcing/conditions using WA-DOE data, then run in
  a prognostic mode with climatological seasonal
  cycle/interannual forcing for 1992-1999

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Model Schematic
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The Model has significant hindcast skills at
interannual timescales
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Observed and Simulated Surface and Deep Salinity
in Three Basins, 1992-1999
Salinity (PSU)
Year
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River Inflow into Whidbey Basin and Inflow into
Three Deep Boxes, 1992-1999
Volume Transport (cubic meters per second)
Year
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Sensitivity of Deep Inflow to Variations in River
Discharge and External Salinity
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November freshet enters from Whidbey Basin to
Admiralty Inlet
Density contrast between Admiralty Inlet and Main
Basin reduced/reversed
Inflow from Admiralty Inlet to Main Basin is
reduced/reversed
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Summary

• A simple predictive box model of Puget Sound
  circulation with river and external salinity
  forcing has been constructed. The model can
  reproduce seasonal cycle of salinity variation,
  and is demonstrated to have hindcast skills at
  interannual timescales.
• Variability in river inflow modulates the
  exchange circulation significantly at
  intraseasonal timescales. Interannual variability
  of salinity appears to result from year-to-year
  variability of high discharge events.
• Increased discharge from the Skagit River in late
  Fall enters the Admiralty Inlet relatively
  undiluted, where it encounters strong mixing. The
  resultant freshening of the inflow layer causes
  the deep inflow into the Main Basin to halt
  temporarily and even reverse. The inflow however
  recovers within two months.