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					Committee Meeting
   9 Jun 2003


         Alfredo López de Aretxabaleta
                 Outline

• Georges Bank assimilation experiment
  (GLOBEC)
     • Progress towards poster (GRC) and paper


• SABLAM
     • Preliminary questions
     Tentative structure of dissertation

      Effects on crosshelf transport of persistent
         baroclinic features on the coastal ocean

1. Introduction
2. Georges Bank tidal front: effects on the retention of
   passive drifters
3. SAB inner shelf filaments basic characteristics:
   persistence and evolution
4. SAB inner shelf filaments effects on crosshelf transport
5. Conclusions
 Hindcasting May 1999 on the
Southern Flank of Georges Bank:
     frontal circulation and
          implications
2. Georges Bank tidal front: effects on
   the retention of passive drifters

May 1999 experiment: Position and evolution of the
  tidal front and its influence on the retention of
  larval fish.
•   Wind forcing and heat flux effects
•   Internal parameters study (EKMIN, AK…)
•   Data assimilation improvements
•   Particle track simulations
Georges Bank Experiment




Vrms = 0.42 m/s       Vrms = 0.08 m/s
Signal Size       Misfit Size (Obs-Mod)
                            (Lynch and Hannah, 1999)
Methods
Misfit Reduction
Misfit Reduction
Skill Level of Simulation




 Published skill  3.4 Km/day
 Current Best Skill  2.34 Km/day
CTD casts positions
        Model /CTD comparison




Using observed Heat flux (instead of AVN) improves
          model mass structure and skill
Conceptual Tidal Front Diagram




                         (Lough and Manning, 2001)
Best Prior Estimate
Passive Drifter Simulations
         Structure of poster/paper

1. Introduction
  •     Starting point: Lynch et al (2001)
  •     Physical conditions: Seasonal structure, tidal dynamics,
        frontal position…

2. Observations (Jim Manning)
  •     CTD
  •     ADCP
  •     Drifters

3. Model
  i.    Best Prior Estimate
            •    Wind forcing and heat flux effects
            •    Internal parameters study (EKMIN, AK…)
  ii.   Data Assimilation
            •    Truxton
            •    Casco
       Structure of poster/paper


4. Results
  •   Mass field (T, S, ρ) (Front position)
  •   Vertical structure (U, V, W, turbulence???)
  •   Particle tracks simulations

5. Discussion
  •   Frontal jet
  •   Secondary circulation
          •     Near-surface convergence
          •     Downwelling
          •     Near-bottom divergence

6. Conclusions
SAB “inner” shelf filaments
Filaments
3. SAB inner shelf filaments basic
   characteristics: persistence and evolution
- Justification: Previous SkIO SST work
- Does the presence of the filaments increase T, S
   variability on the region? (EOF, principal component
   analysis) If so, how?
- Temporal, spatial scale (3-D structure)
- Possible physical mechanisms
- Evolution
Limiting factor: Availability of data (NODC, towers, tow
   body, cruises CTD…)
Variability


                             ½ x ½ deg
                              squares



                                Bottom
                                depth:
                                <400m
                                >400m




              Data from NODC TS database
Filaments




             Vertical
            structure
                ?
Jan 02 Filament
Jan 02 Filament
Jan 02 Filament
Jan 02 Filament
Jan 02 Filament
    Jan 02 Filament




Relaxation of shelf to wind event:
 Possible generation mechanism
4. SAB inner shelf filaments effects on
   crosshelf transport
•   Basic box simulations
        •   Barotropic
        •   Climatology
        •   Improved mass field
•   Effect of heat flux
•   Effect of river discharge
•   Effect of atmospheric features (Pat Welsh Gulf of
    Mexico continuation front)
•   Validation of model results
•   Implications on primary and secondary production
    (Passive drifters simulations)
              Filaments

 Basic Box
 Transport
Simulations
Preliminary Barotropic Model Results




   Barotropic Q5 run forced with R2 observed wind
Preliminary Barotropic Model Results




         Barotropic Q5 run forced with
       simulated along-shelf wind event
    Key literature on coastal fronts
             and filaments
• Haidvogel, Beckmann & Hedstrom JGR, 1991
  (filament formation and evolution)
• Li, Nelson & Koziana GRL,2003 (SST)
• Blanton, Oey, Amft & Lee JPO,1989 (coastal front)
• Blanton, Werner, Kim, Atkinson, Lee & Savidge Cont.
  Shelf Res. 1994 (transport in front)
• Chen JPO,2000 (low salinity cells)
•
            TIMELINE


• GB data assimilation
    • Poster (Jun15)
    • Paper (??)
• SAB structures
    • Variability
    • Data analysis
    • Model simulations
       Remaining questions


• Master bypass
• Orals
• ???

				
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