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WORKSHOP ON HYPOXIA IN NARRAGANSETT BAY OCTOBER 2 , 2006 - FIELDWORK IN SUPPORT OF

WORKSHOP ON HYPOXIA IN NARRAGANSETT BAY OCTOBER 2 , 2006 - FIELDWORK IN SUPPORT OF HYDRODYNAMIC MODELS. Large Scale CTD Surveys - Deacutis, Murray, Prell Moored + Vessel-based Circulation Studies – Kincaid, Bergondo Towed Undulator Surveys - Ullman

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WORKSHOP ON HYPOXIA IN NARRAGANSETT BAY OCTOBER 2 , 2006 - FIELDWORK IN SUPPORT OF

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  1. WORKSHOP ON HYPOXIA IN NARRAGANSETT BAY OCTOBER 2 , 2006 - FIELDWORK IN SUPPORT OF HYDRODYNAMIC MODELS • Large Scale CTD Surveys - Deacutis, Murray, Prell • Moored + Vessel-based Circulation Studies – Kincaid, Bergondo • Towed Undulator Surveys - Ullman • Moored Vertical Profilers – Vaudrey, Kremer

  2. “The Day Trippers” – Large Scale CTD Surveys 2006 Survey Dates : Neap Tide Surveys : 6/6/06, 7/6/06, 8/3/06,8/31/06 Spring Survey : 8/11/06

  3. PRN 1 PRS 07 http://www.geo.brown.edu/georesearch/insomniacs/

  4. Deanna Bergondo & Chris Kincaid – Bottom Mounted ADCP Sites

  5. Providence River Bottom Mounted ADCPs Influenced by wind

  6. Providence River Bottom Mounted ADCPs Outflow Inflow

  7. Providence River Bottom Mounted ADCPs Outflow Inflow

  8. Providence River Bottom Mounted ADCPs

  9. Summary Bottom Mounted Results • EYC shallows – average surface flow to North • Influenced by prevailing winds • Two layer flow in EYC and Conimicut channels • Southward winds enhance return flow • Northward winds stall return flow

  10. Physics: Observations & Modeling Acoustic Doppler Current Profilers - C Kincaid Bottom mounted Ship mounted Data coverage: Excellent temporal Poor Spatial Data coverage: Good spatial Poor Temporal

  11. Results: Providence River Prevailing outflow - shallow, western side shipping channel Prevailing inflow - deep, eastern side shipping channel Series of weak, recirculation eddies in shallow edges Strong wind-induced water column response/reorientation Physics: Goal to characterize circulation, mixing, flushing, transport, etc Methods are Observations & Modeling

  12. Bay Circulation Data Summary: Model boundary conditions 18 underway surveys: summer vs winter

  13. Bay Circulation Data Summary: Model boundary conditions 18 underway surveys: summer vs winter 1.5 years of BM-ADCP data

  14. Bay Circulation Data Summary: Model boundary conditions Summer: strong long-shore flow bottom surface

  15. Bay Circulation Data Summary: Model boundary conditions Summer: prevailing (depth-averaged) counter-clockwise flow Summer: strong long-shore flow

  16. Bay Circulation Data Summary: Model boundary conditions Summer: prevailing (depth-averaged) counter-clockwise flow (CCF) Dominant exchange through mouth Summer: strong long-shore flow

  17. Bay Circulation Data Summary: Model boundary conditions Strong wind-induced exchanges

  18. Bay Circulation Data Summary: Model boundary conditions Extent of counter Wind Strong wind-induced exchanges SE winds enhance CCF, trigger RIS intrusion

  19. Bay Circulation Data Summary: Model boundary conditions Extent of counter Spatial extend of CCF ? ? Wind Strong wind-induced exchanges SE winds enhance CCF, trigger RIS intrusion

  20. Bay Circulation Data Summary: Model boundary conditions Extent of counter Winter: Strong 2-layer flow RIS water from southwest

  21. Bay Circulation Data Summary: Model boundary conditions Mt. Hope Bay circulation/exchange /mixing study. ADCP, tide gauges (Deleo, 2001) Extent of counter Bay-RIS exchange study (98-02)

  22. Bay Circulation Data Summary: Model boundary conditions Narragansett Bay Commission: Providence & Seekonk Rivers Mt. Hope Bay circulation/exchange /mixing study. ADCP, tide gauges (Deleo, 2001) Extent of counter Bay-RIS exchange study (98-02)

  23. This project: Mid-Bay focus Narragansett Bay Commission: Providence & Seekonk Rivers Mt. Hope Bay circulation/exchange /mixing study. ADCP, tide gauges (Deleo, 2001) Extent of counter Summer, 07: 4 month deployment (Outflow pathways) Bay-RIS exchange study (98-02)

  24. This project: Mid-Bay focus Outflow, inflow, exchange between Bay sub-regions Narragansett Bay Commission: Providence & Seekonk Rivers Mt. Hope Bay circulation/exchange /mixing study. ADCP, tide gauges (Deleo, 2001) Extent of counter Summer, 08: Deep return flow processes Bay-RIS exchange study (98-02)

  25. High-Resolution Surveys of Hydrography, Currents, and Vertical Mixing Dave Ullman (GSO) • Objectives: • Provide high resolution sections of physical • and biological parameters for assessment and • calibration of hydrodynamic and ecological models. • Estimate vertical turbulent mixing rates. • Methodology: • Towed undulating vehicle measuring hydrographic • parameters and turbulent microstructure. • Shipboard ADCP measuring currents.

  26. Acrobat Microstructure Sensors. Towed Undulating Vehicle • Towed vehicle sensors: • Temperature • Conductivity • Pressure • Oxygen concentration • Chlorophyll fluorescence • Nitrate concentration • Microscale conductivity • (turbulent mixing) • Ship-mounted ADCP: • Velocity profiles

  27. Along-channel sections suggest dynamical importance of the “narrows” at Conimicut Rapid variability in depth of thermocline, halocline over short distances. Conimicut

  28. Coordinate origin Conimicut Pt. Intensive Sampling, Conimicut Region • Carried out repeated tows over approximately a full tidal cycle • along black line shown on bathymetry map: • August 11, 2005 (Neap): 18 lines • August 18, 2005 (Spring): 20 lines

  29. Flood Tide Eddies • Commonly observed just south of narrows at Conimicut on flood tide. • Cause as yet unknown. • Potential to be an important horizontal dispersal mechanism. Aug. 11, 2005 early flood Clockwise eddy in near-surface current (blue vectors) Extends down to ~7 m depth. East Component (m/s) North Component (m/s) Conimicut south

  30. Acrobat Signature of Eddies in Hydrographic Fields? T Doming of isolines in upper water column in eddy region. S ADCP Eddy East Component (m/s) O2 Chl-a North Component (m/s) NO3

  31. Vertical Mixing Estimates • Methodology: • Compute variance of conductivity gradient. • Apply corrections for salinity contributions • and sensor response to get temperature • gradient variance. • Dissipation rate of temperature gradient • fluctuations (T) is proportional to variance. • Estimate vertical temperature gradient ( ) • from CTD sensors on acrobat. • Turbulent thermal eddy diffusivity • computed from T and gradient: • Micro-conductivity Sensor on Acrobat: • Measures conductivity at scales of O(1cm). • Sampled at 1024 Hz.

  32. Example Vertical Diffusivity Section From a single tow on Aug. 18, 2005. Spring tide conditions, ebb flow. Colors: log10(KT) (m2/s) Lines: t (kg/m3) • Conimicut narrows: • KT~10-4 - 10-3 m2/s • (strong vertical mixing) south

  33. Tidally Averaged Vertical Turbulent Diffusivity Colors: log10(KT) (m2/s) Lines: t (kg/m3) Aug. 11 (neap) Aug. 18 (spring) • Turbulent mixing appears to be enhanced in the Conimicut area. • Slightly stronger mixing on spring tides: • Neap average = 2.9x10-5 m2/s. • Spring average = 3.5x10-5 m2/s.

  34. Future Interaction with Modelers • Compare observations to ROMS model output: • Tidal eddies • Present in model? • If so, what is the mechanism by which they form? (Examine model momentum balance) • How do they affect horizontal property transport? • Vertical mixing • How does magnitude of model vertical mixing (computed by turbulence closure submodel) compare with observed mixing rates? • Can observations be used to tune model turbulence parameterizations? • Stratification • Is model vertical stratification of similar magnitude as observed?

  35. J. Kremer & J. Vaudrey Profiling Units 4 Locations Field’s Point Bullocks Reach Buoy east of Conimicut Point Light Warwick Neck Sampling Set-Up sample every 15cm in the vertical 1 profile every 3 hours deployed for ~ 2 weeks 3 Deployments June, July, September

  36. Temperature oC depth off the bottom (m) Salinity ppt Dissolved Oxygen mg/L day of deployment (day 1 = 8/31/06) east of Conimicut Light

  37. Warwick Neck Temperature oC depth off the bottom (m) Salinity ppt Dissolved Oxygen mg/L day of deployment (day 1 = 6/27/06; day 16 = 7/13/06)

  38. END

  39. Hydrodynamic Model Grid Resolution: 100 m Grid Size: 1024 x 512 Vertical Layers: 20 River Flow: USGS Winds: NCDC Tidal Forcing: ADCIRC Open Boundary

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