1. Deep-water Intrusions in the Puget Sound Sally Warner Coastal & Estuarine Fluid Dynamics class Friday Harbor Labs Summer 2006

2. Project goals - Was an intrusion of dense ocean-water occurring during our 36-hour cruise? - What processes were working to allow or prevent this intrusion?

3. Estuary dynamics

4. Fjord dynamics

5. Why are intrusions essential to fjords? What happens in the Puget Sound? What controls the onset of intrusions? Intrusions

6. Puget Sound and Admiralty Inlet depth

7. 30.8 psu The Intrusion 30.8 psu water intruding down the estuary side of the sill

8. Barotropic vs. Baroclinic Forcing 31.2 Advection distance of 31.2 psu water: 3.89 and 4.03 km in 5.3 and 5.0 h. Tidal current time t1t1 t0t0 t2t2 Barotropic excursion distance Barotropic excursion lengths: 0.95 and 1.60 km

9. ADCP velocity u baroclinic = 25 cm s -1 Baroclinic circulation is essential for the propagation of the intrusion t3t3 u barotropic = 27 cm s -1

10. Historical Data: s x vs. mixing 38 historical transects and our cruise “Bottom water renewal is controlled by changes in the intensity of mixing due to fortnightly variations in the tidal amplitude.” Geyer & Cannon (1982) “The onset of intrusions is a result of the fluctuations in the horizontal density gradient caused by salinity variations across the sill.” Cannon et. al. (1990) Our cruise: slack = 14 h s = 1.5 psu, s x =0.03 psu km -1

11. Conclusions - Yes, an intrusion was occurring when we visited Admiralty Inlet - Reduced tidal velocities allowed baroclinic circulation to develop which carried 30.8 psu water over the sill. - Both the spring/neap change in tidal energy and variation in the horizontal salinity gradient are important mechanisms controlling intrusions of deep water into the Puget Sound, as seen from historical data.