Direct observations of estuarine dispersion results of a recent dye experiment
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Direct observations of estuarine dispersion: results of a recent dye experiment. Bob Chant Rutgers University. River. Pritchard’s Paradigm. Seaward at the surface. Pressure gradient and Velocity. But estuaries are often highly 3-dimensional with appreciable

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Direct observations of estuarine dispersion results of a recent dye experiment

Direct observations of estuarine dispersion:

results of a recent dye experiment

Bob Chant

Rutgers University


Direct observations of estuarine dispersion results of a recent dye experiment

River

Pritchard’s Paradigm

Seaward at

the surface

Pressure gradient and Velocity


Direct observations of estuarine dispersion results of a recent dye experiment

But estuaries are often highly 3-dimensional with appreciable

cross channel gradients of salinity and velocity.

Do these processes impact stream-wise dispersion?

Not a new question-- But observations are lacking.

Current understanding is based on models (Zimmerman, Okubo, Fischer, Smith)

or indirect methods.


Direct observations of estuarine dispersion results of a recent dye experiment

“Lagrangain studies of secondary circulation and mixing in a stratified channel”

NSF PI’s Chant, Geyer and Houghton.

Salinity section May 21, 2001

2-days prior to injection


Direct observations of estuarine dispersion results of a recent dye experiment

Pilot Dye Study May 23-24, 2001. 4 more experiments planned for May, 2002

Pilot study coincided with microstructure measurements by Hartmut Peters.

2002 injections

will occur at

spring and neap tide conditions


Direct observations of estuarine dispersion results of a recent dye experiment

Ship Track and Dye Trace

Currents and salinity

Injection May 23, 2001

9:15-9:30 AM

Salinity and velocity cross

sections at time of release

Figure 2 Study Site


Direct observations of estuarine dispersion results of a recent dye experiment

Dye’s salinity distribution at

release

Currents and salinity

Upper layer

Lower layer

39 kg of fluorecene dye


Direct observations of estuarine dispersion results of a recent dye experiment

Patch 2 (12:20 - 14:00)

Depth integrated dye

1.8 kg

26 kg


Direct observations of estuarine dispersion results of a recent dye experiment

40.94

40.9

Cross Channel Sections during Flood

2 hours after release


Direct observations of estuarine dispersion results of a recent dye experiment

Patch 2 (12:20 - 14:00)

Integrated dye above 14 psu

Depth integrated dye

26 kg

1.8 kg


Direct observations of estuarine dispersion results of a recent dye experiment

25 kg

26 kg

Patch 3

Patch 2


Direct observations of estuarine dispersion results of a recent dye experiment

Patch 3 (14:00 - 15:40)

Depth integrated dye

Integrated dye above 14 psu

2.3 kg

25 kg


Direct observations of estuarine dispersion results of a recent dye experiment

44 kg

Patch 3 (14:00 - 15:40)

Patch 4 (15:00 - 17:10)

Depth integrated dye

Depth integrated dye


Direct observations of estuarine dispersion results of a recent dye experiment

A series of cross-channel section during late ebb

Currents from ADCP


Direct observations of estuarine dispersion results of a recent dye experiment

1

5

8

6

2

1

7

3

8

4


Direct observations of estuarine dispersion results of a recent dye experiment

Patch 4 (15:00 - 17:10)

Integrated dye above 14 psu

Depth integrated dye

16 kg

44 kg


Direct observations of estuarine dispersion results of a recent dye experiment

1

0.5

0


Direct observations of estuarine dispersion results of a recent dye experiment

Vertical mixing estimates


Direct observations of estuarine dispersion results of a recent dye experiment

H > 10 m

H < 10m

<S>=15.8

<S>=15.5

we=0.09 mm/s

Kv=2.3* 10-3 m2/s

we=0.05 mm/s

Kv= 1.0-3 m2/s

<S>=15.4

<S>=15.2

we=0.05 mm/s

Kv=1.7* 10-3 m2/s

we=0.28 mm/s

Kv=1.0* 10-2 m2/s

<S>=15.2

<S>=14.4

Max Ebb

we=0.3 mm/s

Kv=1.3* 10-2 m2/s

we=0.31 mm/s

Kv=1.1* 10-2 m2/s

<S>=14.2

<S>=13.3

Max Flood


Direct observations of estuarine dispersion results of a recent dye experiment

1

0.5

0

?

Slack before flood

Day 1

Slack before ebb

Day 2


Direct observations of estuarine dispersion results of a recent dye experiment

+.5

12

16

m/s

-1.0

Current

May 24

30 hours after release

End of Ebb


Direct observations of estuarine dispersion results of a recent dye experiment

FLOOD

Along Channel sections during ebb

14:00 - 14:30

14:54 - 15:21

15:41 - 16:30

Dye Contour Intervals 0.2, 0.5, 1.0 2.0


Direct observations of estuarine dispersion results of a recent dye experiment

Patch 5 (15:45 - 18:45)

Integrated dye above 14 psu

Depth integrated dye

40 kg

20 kg


Direct observations of estuarine dispersion results of a recent dye experiment

Conclusions

1) Lateral iso-pycnal advection of dye on flood

2) Mixing rates on flood are 10-3 and confined to bbm, suggestive of weak

entrainment rates and thickening of BBL is due to flow convergence.

3) Mixing increases an order of magnitude on ebb. Diapycnal

transport occurs primarily on flank

4) Perfect dispersive process-- coupling between secondary

flow spatial variations in mixing and strong ebb shears. Suggests

artificial decomposition of diffusive processes is ...

5) Dye distribution after one tidal cycle is not consistent with simple

tidal straining ideas.

6) While spread of dye is consistent with advection by estuarine flows (but mixing

may not be correct) observations clearly show that dispersion of dye is due to a 3-D

tidal straining effect. Are estuarine flows then influenced by this mixing process?

7) Closure over-entrains on flood.


Direct observations of estuarine dispersion results of a recent dye experiment

Fresh

Salty


Direct observations of estuarine dispersion results of a recent dye experiment

2

1

1

3

5

4

5

40 kg

16 kg

3

2

4

26 kg

25 kg

44 kg

Max 35

36 kg


Direct observations of estuarine dispersion results of a recent dye experiment

Simulation of Dye Release in Hudson

Ebb

Flood

*Simulation by Rocky Geyer


Direct observations of estuarine dispersion results of a recent dye experiment

Patch 1 (11:00 - 12:15)

Integrated dye above 14 psu

Depth integrated dye

16 kg

0.6 kg


Direct observations of estuarine dispersion results of a recent dye experiment

* H > 10m

* H < 10m

Dye weighted salinity of each cast


Direct observations of estuarine dispersion results of a recent dye experiment

.. Or is it driven by secondary

circulation and mixing on

the margins?

“Lagrangain studies of secondary circulation and mixing in a stratified channel”

NSF PI’s Chant, Geyer (WHOI) and Houghton (LDEO)

Is diapycnal transport primarily associated

with vertical mixing?

Note: May dominate diapycnal

mixing process in global ocean


Direct observations of estuarine dispersion results of a recent dye experiment

End of Ebb

End of Flood

End of Flood


Direct observations of estuarine dispersion results of a recent dye experiment

Two crude estimates of effective horizontal dispersion….

…both suggest Aeff=1000 m2/s

30 hours after release


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