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Modeling Puget Sound’s Circulation and its Variability Ocean 520 Seminar December 11, 2002. Mitsuhiro Kawase School of Oceanography, University of Washington. A Modeling Partnership for Puget Sound Puget Sound Circulation Model: Status Tidal Currents and Mixing Exchange Circulation

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modeling puget sound s circulation and its variability ocean 520 seminar december 11 2002

Modeling Puget Sound’s Circulation and its VariabilityOcean 520 SeminarDecember 11, 2002

Mitsuhiro Kawase

School of Oceanography, University of Washington

slide2
A Modeling Partnership for Puget Sound
  • Puget Sound Circulation Model: Status
    • Tidal Currents and Mixing
    • Exchange Circulation
    • Seasonal Cycle
  • Interannual Variability in Puget Sound
slide3

Whole Sound

(UW-PRISM/KC-DNR)

Duwamish Estuary/

Elliott Bay

(KC-DNR)

Dyes/Sinclair Inlet

(PSNS)

South Sound (WA-DOE)

Modeling Efforts in Puget Sound

slide4

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

slide5

Partnership Objectives

  • Develop, maintain and operate a system of simulation models of Puget Sound’s 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 Sound’s working, and address questions raised by the regional community concerning management of the Sound and its resources.
slide6
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

slide7

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
slide8

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
uw prism puget sound circulation model
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)
tidal currents

Tidal Currents

Admiralty Inlet

Triple Junction

Tacoma Narrows

Animations by Christian Sarason, OIP

strong currents at the sills generate vigorous turbulent mixing
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
exchange circulation
Exchange Circulation
  • Point Edwards
  • Possession Sound
average along channel flow at point edwards june 28 july 27 2000

Outflow core on the east side

(cm/s)

Slanted level of

No motion

(cm/s)

Observed

Model

Inflow intensified on the Kitsap side

Inflow core at the bottom

Average Along-channel Flow at Point Edwards, June 28- July 27, 2000
average along channel flow in possession sound november 25 december 24 2000

Outflow intensified on Whidbey side

Three layer flow

(cm/s)

(cm/s)

Observed

Model

Inflow intensified on Snohomish side

Average Along-channel Flow in Possession Sound, November 25 - December 24, 2000
seasonal cycle

Seasonal Cycle

Saratoga Passage

(WA-DOE SAR 003)

Point Jefferson

(KC-DNR KSBP01)

summary puget sound circulation model status
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
slide23

Salinity 1999

32

32

32

30

30

30

June

28

28

28

Dalco Passage

Admiralty Inlet Sills

Main Basin

SJDF

December

slide24

Salinity 2000

32

32

30

30

June

28

28

Dalco Passage

Admiralty Inlet Sills

Main Basin

SJDF

December

slide28

Temperature Anomaly in Puget Sound and Pacific Decadal Oscillation

R=0.57 (33% of variance)

slide29

How sensitive is the Sound’s 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

slide30
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
slide31

Strait of

Juan de Fuca

Rivers

Whidbey

Advection

Admiralty

Inlet

Main

Basin

N. Hood

Canal

South

Sound

Vertical

Mixing

S. Hood

Canal

Model Schematic

slide34

River Inflow into Whidbey Basin and Inflow into Three Deep Boxes, 1992-1999

Volume Transport (cubic meters per second)

Year

slide36

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

summary
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.