OceanographyOceanography

Interdisciplinary approach for Interdisciplinary approach for observing the water column observing the water column and benthic interactionsand benthic interactions

Cruise on the R/V SavannahCruise on the R/V Savannah

Sampling sites and techniquesSampling sites and techniques

Let’s Get PhysicalLet’s Get Physical

The Intellectual Upwelling The Intellectual Upwelling Group:Group:

John BallardJohn BallardKaren PuckettKaren PuckettSierra LynchSierra Lynch

GoalsGoals

Explain the structure of water Explain the structure of water masses observed during the cruise masses observed during the cruise (June 19-20, 2008)(June 19-20, 2008)

Examine physical influences of the Examine physical influences of the water column on the physical benthic water column on the physical benthic environmentenvironment

Station 1 Station 2

Station 3 (R2)

Station 4

Station 5

Station 1 Station 2

Station 3 (R2)

Station 5

Station 4

Station 1 Station 2

Station 3 (R2)

Station 5

Station 4

R2 Surface Temperature and Salinity Averages for each day from 1999-2007.

10

15

20

25

30

35

40

Date (m/d/year)

Sal

init

y (p

pt)

/ T

emp

erat

ure

(C

)

SalinityTemperature

Hypothesis: Potential Gulf Stream meander and eddy-induced upwelling

Lee et al 1991

Winds from the Winds from the SouthwestSouthwest

Blanton et al 2003

NutrientsNutrients• [NO[NO33]= 53.0 – 2.6T (Lee et al 1991)]= 53.0 – 2.6T (Lee et al 1991)• Colder water=Higher nitrogen Colder water=Higher nitrogen

(nutrients)(nutrients) Chlorophyll Chlorophyll

Onshore currents Onshore currents south of 30˚ latitudesouth of 30˚ latitude

Alongshore currents Alongshore currents 31˚ to 32˚ latitude31˚ to 32˚ latitude

Offshore currents Offshore currents after 33˚after 33˚

Beginning in June

Aretxabaleta et al 2007

Assumptions and LimitationsAssumptions and Limitations• TimeTime• Number of ProfilesNumber of Profiles

• DataData• Small Temperature Small Temperature

GradientGradient

Benthic and Water Column Benthic and Water Column InteractionsInteractions

Mid-shelf currents are wind driven (Blanton Mid-shelf currents are wind driven (Blanton et al 2003)et al 2003)

Does water movement affect ripple Does water movement affect ripple formation?formation?

Ripples are important for nutrient Ripples are important for nutrient circulationcirculation

Figure 1. The Effect of Wind Stress on Wave Height at R2 for 2007

y = 0.0159e0.1997x

R2 = 0.5548

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 2 4 6 8 10 12 14 16 18 20

Wind Stress (N/m²)

Wav

e H

eigh

t (m

)

Ripple Size 1

Ripple Size 2

Wave Height v Ripple Direction

0

0.5

1

1.5

2

2.5

3

3.5

4

Date

Wav

e H

eigh

t (m

)

0

1

2

3

4

Rip

ple

Dir

ectio

n

Wave Height

Ripple Direction

NW & SE

N & S

NE & SW

E & W

Stable Summer Winds

Ripple Size 1

Ripple Size 2

Wave Height v Ripple Size

0

0.5

1

1.5

2

2.5

3

3.5

4

Date

Wav

e H

eig

ht

(m)

0

1

2

3

4

5

Rip

ple

Siz

e

Wave Weight

Ripple Size

Advection in the Boundary LayerAdvection in the Boundary Layer

Huettel and Rusch 2000

•Low Pressure pulls nutrients up to water column

•High Pressure pushes POM and DOM down

•Advection stronger with increased ripple height, current strength, and grain size

Bringing it all togetherBringing it all together

Upwelling moving onshore bringing Upwelling moving onshore bringing nutrients from deep ocean nutrients from deep ocean

Wind driven mixing and potential Wind driven mixing and potential advection of sediment circulate advection of sediment circulate nutrients in the mid-shelfnutrients in the mid-shelf

Emma Paz © 2008