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Ocean Physics. Ocean Physics. Buoyancy Temperature Light Density Pressure Depth Salinity Sound Dissolved Gasses. Buoyancy. Archimedes Principle of Buoyancy A floating object displaces a volume of fluid equal in mass to the floating object. empty. loaded with fish. Displaced water.

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slide2

Ocean Physics

  • Buoyancy
  • Temperature
  • Light
  • Density
  • Pressure
  • Depth
  • Salinity
  • Sound
  • Dissolved Gasses
slide4

Archimedes Principle of Buoyancy

A floating object displaces a volume of fluid equal in mass to the floating object

empty

loaded with fish

Displaced water

slide5

Objects that are more dense than water will sink.

  • Objects that are less dense than water will float.
  • Objects that are the same density as water will neither sink nor float.

float

Neutrally

buoyant

sink

slide6

Organisms adaptation to buoyancy in water

  • Blubber
  • Swim bladder
  • Pneumatophore
slide7

Organisms adaptation to buoyancy in water

  • Air chambers
  • Large liver & heterocercal tail
  • Buoyancy Compensator Device (BCD)
slide9

polar

temperate

tropic

temperate

polar

Isotherms

60o

30o

0o

30o

60o

Lines of equal temperature

the electromagnetic radiation spectrum
The Electromagnetic Radiation Spectrum

Only green and blue wavelengths pass through water a great distance.

light absorption in the ocean
Light Absorption in the Ocean
  • Light Intensity
    • decreases with depth
    • 0-100 m (photic zone)
    • 100-1000m (dysphotic zone)
    • >1000 (aphotic zone)
light penetration in the ocean
Light Penetration in the Ocean

Wavelength (nm)

400

500

600

700

0 m

Photic Zone

Photosynthesis

100m

No Photosynthesis

Dysphotic Zone

1000m

Aphotic Zone

~65% of visible light is absorbed in the 1st m

light absorption in the ocean15
Light Absorption in the Ocean
  • Spectral Characteristics
    • red wavelengths absorbed more readily by water than blue wavelengths
    • blue light penetrates deepest in the oceans
slide16

Light effects organisms residing in the photic and aphotic zone.

  • Phytoplankton productivity
  • Algae- green, brown, red
  • Predator/Prey relationships
  • Diurnal vertical migration
  • Bioluminescence- luminescent organs on underside mimic downwelling light
slide17

Refraction- as light enters the water, it bends; this is due to light traveling through different densities

Light entering the ocean is weakened by scattering and absorption.

slide19

Density

1 ft

1 ft

1 ft

Air

0.08 lbs

fw

62.4 lbs

sw

64 lbs

1 ft

1 ft

1 ft

Piston example:

Air is compressible

Water is incompressible

slide20

64 lbs

Water doesn’t change density under pressure

64 lbs

slide21

Temperature SalinityDensity

Low High Low High Low High

surface

0 m

100 m

1000 m

thermocline

halocline

pycnocline

Thermocline + Halocline = Pycnocline

slide23

Sound in Water

Speed of sound- faster in ocean (higher density)

1500 m/sec, which is 4x faster than in air

Difficult to determine direction of sound

Can hear many things such as ships miles away, shrimp eating, helicopters overhead, and whales communicating.

source of noise

slide24

Speed of Sound (m/sec)

1,475

1,500

0

1000

2000

3000

4000

high speed

min speed

sofar layer

Depth (m)

high speed

slide25

SOFAR Channel

Distance

0

500

1000

1500

2000

sound rays

Depth (m)

SOFAR channel

slide26

Sofar Layer

  • The depth at which the speed of sound is minimum; Thus, loud noises can be heard for thousands of km
  • Sound generated by Navy test in Indian Ocean at sofar layer was heard as far away as the Oregon coast. May affect behavior and anatomy of marine organisms
slide28

Solubility of Gases in Seawater as a Function of Temperature (salinity @ 33o/oo)

Solubility

(ml/l at atmospheric pressure)

Temperature N2 O2 CO2

(oC) .

0 14.47 8.14 8,700

10 11.59 6.42 8,030

20 9.65 5.26 7,350

30 8.26 4.41 6,660

slide29

Relationship between water depth, pressure, and volume

Air weighs 14 lbs/in2 (psi)

Absolute pressure is the combined pressure of water and air

Depth

0 ft

33 ft

66 ft

99 ft

Absolute Pressure

1 atm 14.7 psi

2 atm 29.4 psi

3 atm 44.1 psi

4 atm 58.8 psi

Volume

x1

x 1/2

x 1/3

x 1/4

slide30

Boyle’s Law

For any gas at a constant temperature, the volume will vary inversely with absolute pressure while the density will vary with absolute pressure.

I.e., volume  with  pressure

 pressure  density

daltons law of partial pressure
Daltons Law of Partial Pressure

The total pressure of a gas exerted by a mixture of gas is the sum of the gases exerted independently.

Air % partial pressure (mm Hg)

N2 78.6 597

O2 21.0 159

CO2 0.04 0.3

H2O 0.46 3.7

Total 100 760

Partial pressure is directly related to its % in the total gas mixture. E.g., at 1 atm PO2 = 159 mm Hg

slide32

Henry’s Law

When a mixture of gas is in contact w/a liquid, each gas will dissolve in the liquid in proportion to its partial pressure.

Gasses can go in and out of solution

e.g., open soda, get CO2 bubbles (CO2 is under pressure)

Increase pressure, increase concentration

slide33

Dissolved gasses in seawater:

Seawater Air

N2 48% 78%

O2 36% 21%

CO2 15% 0.04%

slide34

Gas Solubility vs Temperature

Honaunau Tide Pool

Gasses dissolve most readily in cold water

slide35

Decompression sickness

  • It is caused when N2 enters the blood circulation and the tissues.
  • When extra N2 leaves the tissues, large bubbles form. N2 bubbles can travel throughout the system and into the lungs and blood routes.
  • Treatment: hyperbaric chamber
inquiry
Inquiry
  • What is isostacy?
  • Why do objects in water seen from the surface appear to bend?
  • Which gas is responsible for decompression sickness?
  • If a balloon is brought to 6 atm, what would it’s volume be?
  • Which wavelength of light penetrates the ocean the deepest?