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

1) Large Scale CTD Surveys - Deacutis, Murray, Prell

2) Moored + Vessel-based Circulation Studies – Kincaid, Bergondo

3) Towed Undulator Surveys - Ullman

4) Moored Vertical Profilers – Vaudrey, Kremer

“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

PRS 07

PRN 1

http://www.geo.brown.edu/georesearch/insomniacs/

Deanna Bergondo & Chris Kincaid – Bottom Mounted ADCP Sites

Providence River Bottom Mounted ADCPs

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7/7 7/17 7/27 8/6 8/16 8/26 9/5 9/15 9/25 10/5 10/15 10/25

Win

d V

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m/s

)

Bottom Flow

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0

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7/7 7/17 7/27 8/6 8/16 8/26 9/5 9/15 9/25 10/5 10/15 10/25

Vel

ocity

(m

m/s

)Surface Flow

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7/7 7/17 7/27 8/6 8/16 8/26 9/5 9/15 9/25 10/5 10/15 10/25

Vel

ocity

(m

m/s

) EYC-shallow s

Influenced by wind


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7/7 7/17 7/27 8/6 8/16 8/26 9/5 9/15 9/25 10/5 10/15 10/25

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Bottom Flow

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7/7 7/17 7/27 8/6 8/16 8/26 9/5 9/15 9/25 10/5 10/15 10/25

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ocity

(m

m/s

)Surface Flow

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Vel

ocity

(m

m/s

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Outflow

Inflow


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Bottom Flow

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7/7 7/17 7/27 8/6 8/16 8/26 9/5 9/15 9/25 10/5 10/15 10/25

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ocity

(m

m/s

)Surface Flow

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7/7 7/17 7/27 8/6 8/16 8/26 9/5 9/15 9/25 10/5 10/15 10/25

Vel

ocity

(m

m/s

) Conimicut

Outflow

Inflow


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9/5 9/15 9/25 10/5 10/15 10/25

Flo

w (

m3/s

)

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Bottom Flow

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Surface Flow

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Conimicut EYC-deep EYC-shallow s

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

Physics: Observations & Modeling

Acoustic Doppler Current Profilers - C Kincaid

Bottom mounted Ship mounted

Data coverage:Excellent temporalPoor Spatial

Data coverage:Good spatialPoor Temporal

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

Bay Circulation Data Summary: Model boundary conditions

18 underway surveys: summer vs winter


1.5 years of BM-ADCP data

18 underway surveys: summer vs winter


Summer: strong long-shore flow

bottomsurface



Summer: prevailing (depth-averaged) counter-clockwise flow



Summer: prevailing (depth-averaged) counter-clockwise flow (CCF)

Dominant exchange through mouth


Strong wind-induced exchanges


Strong wind-induced exchangesSE winds enhance CCF, trigger RIS intrusion

Wind

Extent of counter


Strong wind-induced exchangesSE winds enhance CCF, trigger RIS intrusion

Wind

?

?

Extent of counterSpatial extend of CCF


Winter: Strong 2-layer flow

RIS water from southwest

Extent of counter


Extent of counterMt. Hope Bay circulation/exchange/mixing study. ADCP, tide gauges (Deleo, 2001)

Bay-RIS exchange study (98-02)




Narragansett Bay Commission: Providence & Seekonk Rivers

This project: Mid-Bay focus




Summer, 07: 4 month deployment (Outflow pathways)

This project: Mid-Bay focus




Summer, 08: Deep return flow processes

Outflow, inflow, exchange between Bay sub-regions

High-Resolution Surveys of Hydrography, Currents, and Vertical Mixing

Dave Ullman (GSO)

Objectives:•Provide high resolution sections of physicaland biological parameters for assessment andcalibration of hydrodynamic and ecological models.•Estimate vertical turbulent mixing rates.

Methodology:•Towed undulating vehicle measuring hydrographicparameters and turbulent microstructure.•Shipboard ADCP measuring currents.

Towed vehicle sensors:•Temperature•Conductivity•Pressure•Oxygen concentration•Chlorophyll fluorescence•Nitrate concentration•Microscale conductivity (turbulent mixing)

Towed Undulating Vehicle

Acrobat

MicrostructureSensors.

Ship-mounted ADCP:•Velocity profiles

Along-channel sections suggest dynamical importance of the

“narrows” at Conimicut

Conimicut

Rapid variability in depth ofthermocline, halocline over short

distances.

Intensive Sampling, Conimicut Region

Conimicut Pt.

Coordinate origin

Carried out repeated tows over approximately a full tidal cyclealong black line shown on bathymetry map:

•August 11, 2005 (Neap): 18 lines•August 18, 2005 (Spring): 20 lines

Flood Tide Eddies

Aug. 11, 2005 early floodClockwise eddy innear-surface current(blue vectors) Extends down

to ~7 m depth.

East Component (m/s)

North Component (m/s)

•Commonly observed just south of narrows at Conimicut on flood tide.•Cause as yet unknown.•Potential to be an important horizontal dispersal mechanism.

Conimicut south

Signature of Eddies in Hydrographic Fields?

East Component (m/s)

North Component (m/s)

T

S

O2

Chl-a

NO3

Doming of isolines in upper watercolumn in eddy region.

ADCP

Acrobat

Eddy

Vertical Mixing Estimates

Micro-conductivity Sensor on Acrobat:•Measures conductivity at scales of O(1cm).•Sampled at 1024 Hz.

Methodology:•Compute variance of conductivity gradient.•Apply corrections for salinity contributionsand sensor response to get temperaturegradient variance.•Dissipation rate of temperature gradientfluctuations (T) is proportional to variance.

•Estimate vertical temperature gradient ( )from CTD sensors on acrobat.

•Turbulent thermal eddy diffusivitycomputed from T and gradient:

T

z

KT T

2T

z

2

Example Vertical Diffusivity Section

Colors: log10(KT) (m2/s)Lines: t (kg/m3)

From a single tow on Aug. 18, 2005.Spring tide conditions, ebb flow.

Conimicut narrows:KT~10-4 - 10-3 m2/s(strong vertical mixing)

south

Tidally Averaged Vertical Turbulent Diffusivity

Aug. 11 (neap) Aug. 18 (spring)

•Turbulent mixing appears to be enhanced in the Conimicut area.

Colors: log10(KT) (m2/s)Lines: t (kg/m3)

•Slightly stronger mixing on spring tides:Neap average = 2.9x10-5 m2/s.Spring average = 3.5x10-5 m2/s.

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) comparewith observed mixing rates? Can observations be used to tune model turbulenceparameterizations?

• Stratification Is model vertical stratification of similar magnitudeas observed?

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

J. Kremer & J. Vaudrey

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

1 2 3 4 5 6 7 8 9 10 11 12 130

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1 2 3 4 5 6 7 8 9 10 11 12 13

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19 20 21 22 23 24 25 26 27 28 29 30 31 32

1 2 3 4 5 6 7 8 9 10 11 12 130

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dep

th o

ff th

e b

otto

m (

m) Temperature

Salinity

DissolvedOxygen

oC

ppt

mg/L

day of deployment (day 1 = 8/31/06)east of Conimicut Light

1 2 3 4 5 6 7 8 9 10 11 12 13

1

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5

19 20 21 22 23 24 25 26 27 28 29 30 31 32

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

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dep

th o

ff th

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otto

m (

m)

Temperature

Salinity

DissolvedOxygen

oC

ppt

mg/L

day of deployment (day 1 = 6/27/06; day 16 = 7/13/06)

Warwick Neck

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

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Grid Resolution: 100 mGrid Size: 1024 x 512Vertical Layers: 20River Flow: USGSWinds: NCDCTidal Forcing: ADCIRC

Open Boundary

Hydrodynamic Model

DYE_08

DYE_02DYE_03

DYE 05

DYE_01

DYE_09DYE_07

DYE_06 DYE 04

Modeling Exchange Between Biological Model Grids

Dye Experiment

Model-Data Comparison

Salinity - Phillipsdale

Sal

inity

(pp

t)

Time (days)

Model

Data

Model-Data ComparisonShallows: North-South Component

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loci

ty

(m/s

)

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serv

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loci

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(mm

/s)

Bottom-model

Bottom

Channel: North-South Component

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10 15 20

Time (days)

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seve

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(m

/s)

Bottom-model

Bottom

Seekonk River

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7/7/06 0:00 7/7/06 12:00 7/8/06 0:00 7/8/06 12:00 7/9/06 0:00 7/9/06 12:00 7/10/06 0:00 7/10/06 12:00 7/11/06 0:00

Time

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rth

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uth

Vel

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mm

/s)

Seekonk River Bottom Mounted ADCPs

Goal: Understand chemistry, biology and physics

of the Bay, at all points in the Bay, for all time

Goal: Understand chemistry, biology and physics

of the Bay, at all points in the Bay, for all time

Goal 2: Understand coupled processes given anycombination of external forcing conditions

Initial Conditions

Forcing Conditions

Output

EquationsMomentum balance x & y directions:u + vu – fv = + Fu + Du t xv + vv + fu = + Fv + Dv t yPotential temperature and salinity :T + vT = FT + DT

t S + v S = FS + DS

t The equation of state:= (T, S, P) Vertical momentum: = - gz o

Continuity equation:u + v + w = 0x y z

Numerical Model

ROMS Model

Regional Ocean Modeling System


3 month BM-ADCPs


3 month BM-ADCPsUnderway ADCPs

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

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