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General Description• Physical and biological processes are inter-related

aspects that govern the productivity of marine ecosystems.

• Provides an introduction to the physical processes that control abundance of marine organisms in the ocean.

• Turbulence in surface and bottom boundary layers and its roles on the lives of plants and animals; buoyancy- and wind-induced circulation, mixing, coastal upwelling/ downwelling processes, fronts, river plume, tides, internal waves, circulation and eddy and their effects on biological transport, primary production; zooplankton, fish and the regeneration of nutrients;

• NPZD (Nutrient, Phytoplankton, Zooplankton and Detritus) chemical-biological model; mathematical and numerical techniques in the of coupled hydrodynamic-ecosystem model.

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Global distribution of chlorophyll averaged over the period from 1 January 2002 to 28 February 2005 using data collected from MODIS on the Aqua satellite. Chlorophyll values range from 0.01 mg/m3 (purple) to 60 mg/m3 (red). From NASA Goddard Space Flight Center.

AMCE608 4Xie, L. and W.W. Hsieh, 1995

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Sun

Food Web

Photosynthesis by phytoplankton

Passed from organism to organism by feeding transfers

Currents, tides (also moon), turbulence and stratification by heating or associated wind*

* 1. Alters boundary layers, stratification and euphotic layer, causes retention of planktonic organisms and modifies light penetration.

2. Transports nutrients and waste products, assists migrations, affects the rate of encounter between planktonic predators and their prey.

3. Rate of biological process is affected by T (C) and organisms colonizing is determined by v (m/s).

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Multi temporal and spatial scales in physic and biologic

processes

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OSU

1mm=10-3m

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Transfers of nutrients and waste products by molecular diffusion

Transfers of nutrients and waste products by faster turbulent diffusion, mesoscale, upwelling, eddy, front, surface and internal waves

Internal Rossby deformation radius=force Coriolis

forcen gravitatio

sin2

'12

h

f

hg

f

c o

h: water depth; ρ: water density; Ω: angular velocity of earth rotation; Φ: latitute

(m)

Transfers of nutrients and waste products by eddy turbulent diffusion,basin scale circulation, plantary waves, tides

Molecular

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About 100 yrs

1-10 yrs

days-1wks

days

hours Time scale

Large marine mammal

Temporal scales determined from organisms

Increase fluctuations in number

Process of trophic transfer

Molecular

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Turbulence, diffusion and boundary layers, mixing, mixed layer

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slowly varying mean fields

rapidly varying turbulent component

Periods of u’: from a second (minimum) to tens minutes (maximum).Size of u’ : from a few millimeters (µm) (minimum) to a few meters (maximum)

Periods

Periods

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Laminar Flow and Turbulent Flow

• The terms laminar flow and purely viscous (molecular) flow are used synonymously to mean a fluid flow which flows in laminas or layers, as opposed to turbulent flow in which the velocity components have random turbulent fluctuations imposed upon their mean values.

• In general, increase the flow will change from laminar to turbulent.

• The effect of viscosity are still present in turbulent flow, but they are masked by much strong turbulence. The viscosity due to turbulent flow is sometimes called as turbulent viscosity.

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Sources of turbulent energy:

1: Instability induced by surface or internal wave breakings,

2: Wind stirring at the sea surface,

3. Velocity shear,

4. Strong currents, meanders and eddies breakings.

Velocity shear

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Definitions:

Viscosity, Friction and Ideal Flow

• Molecular Viscosity: internal friction of fluid due to molecular motion, which causes it resist the tendency to flow. This comes to work when the scale of turbulence is

< 1mm. • Viscous force, i.e. friction depends on the type of fluid and physical

configuration or flow pattern (including both molecular and turbulent viscous force. The magnitude of latter is much larger).

• If the viscous force is negligible, the flow is defined as ideal flow or inviscid flow in which friction is precisely zero.

• A fluid with very small viscosity may behave quite differently to a (hypothetical) fluid with no viscosity at all.

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force viscous

force inertialRe

ud

Reynolds number

u: velocity, d: typical dimension, : viscosity coefficients

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Table 2.1

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Diffusion-Viscosity

• Diffusion: mixing of a property by the random motions of molecules (molecular diffusion) or of eddy (turbulent or eddy diffusion).

Viscosity: it is resistance force of the water, acts to resist the velocity. Its consequence

is corresponding to the associated diffusion.

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Some Estimations

•Fick’s Law: to estimate the flux and time scale of a variable due to molecular diffusion

D

Lt

2

The length scale to diffuse

Coefficient of molecular diffusion=1.5x10-9m2s-1

•Kolmogoroff Length: length scale across the smallest eddy of smallest fluctuation. L=(kinematic viscosity (molecular)/turbulent-energy dissipation)1/4

•Largest turbulent eddies: to determine the vertical excursion of the small passive organisms being moved about by the turbulent flowLb=(turbulent energy dissipation/stratification

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(Bottom) Boundary Layer

• Solid boundary in which water movement is reduced.

It reduces the exchange rate of molecules of O2, CO2, NH3 etc. with the ambient waters.

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No-slip boundary or u=0 at solid surface

Idealized caseReal case