Modeling Puget Sound’s Circulation and its Variability Ocean 520 Seminar December 11, 2002

1. Modeling Puget Sound’s Circulation and its VariabilityOcean 520 SeminarDecember 11, 2002 Mitsuhiro Kawase School of Oceanography, University of Washington

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

3. 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

4. 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

5. 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.

6. 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

7. 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

8. 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

9. 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)

10. Tidal Currents Admiralty Inlet Triple Junction Tacoma Narrows Animations by Christian Sarason, OIP

11. 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

12. Exchange Circulation • Point Edwards • Possession Sound

13. 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

14. 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

15. Seasonal Cycle Saratoga Passage (WA-DOE SAR 003) Point Jefferson (KC-DNR KSBP01)

16. Temperature and Salinity at 100m, off Point Jefferson

17. 2000 Temperature at Point Jefferson, Model-Data Comparison Temperature (C)

18. Model missed a fresh event! Initialization problem 2000 Salinity at Point Jefferson, Model-Data Comparison Salinity (PSU)

19. 2000 Temperature in Saratoga Passage, Model - Data Comparison

20. 2000 Salinity in Saratoga Passage, Model - Data Comparison

21. 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

22. Interannual Variability

23. Salinity 1999 32 32 32 30 30 30 June 28 28 28 Dalco Passage Admiralty Inlet Sills Main Basin SJDF December

24. Salinity 2000 32 32 30 30 June 28 28 Dalco Passage Admiralty Inlet Sills Main Basin SJDF December

25. Salinity Anomaly, Puget Sound Main Basin at 100m

26. R=0.6 (36% of variance)

27. 1997 (ENSO): Year of no density intrusion Salinity and Potential Density in Central Puget Sound, 1990 - 1998(Blue: 100m Red: 200m)

28. Temperature Anomaly in Puget Sound and Pacific Decadal Oscillation R=0.57 (33% of variance)

29. 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

30. 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

31. Strait of Juan de Fuca Rivers Whidbey Advection Admiralty Inlet Main Basin N. Hood Canal South Sound Vertical Mixing S. Hood Canal Model Schematic

32. The Model has significant hindcast skills at interannual timescales

33. Observed and Simulated Surface and Deep Salinity in Three Basins, 1992-1999 Salinity (PSU) Year

34. River Inflow into Whidbey Basin and Inflow into Three Deep Boxes, 1992-1999 Volume Transport (cubic meters per second) Year

35. Sensitivity of Deep Inflow to Variations in River Discharge and External Salinity

36. 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

37. 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.