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Ocean Physics

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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Ocean Physics

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  1. Ocean Physics

  2. Ocean Physics • Buoyancy • Temperature • Light • Density • Pressure • Depth • Salinity • Sound • Dissolved Gasses

  3. Buoyancy

  4. 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

  5. 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

  6. Buoyancy Adaptation • Blubber • Swim bladder • Fatty liver • Buoyancy Compensator Device (BCD)

  7. Temperature

  8. polar temperate tropic temperate polar Isotherms 60o 30o 0o 30o 60o Lines of equal temperature

  9. Sea Surface Temperature July 2005

  10. Properties of Light in the Ocean

  11. The Electromagnetic Radiation Spectrum Only green and blue wavelengths pass through water a great distance.

  12. Light Absorption in the Ocean • Light Intensity • decreases with depth • 0-100 m (photic zone) • 100-1000m (dysphotic zone) • >1000 (aphotic zone)

  13. 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

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

  15. 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

  16. 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.

  17. Density

  18. 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

  19. 64 lbs Water doesn’t change density under pressure 64 lbs

  20. Temperature SalinityDensity Low High Low High Low High surface 0 m 100 m 1000 m thermocline halocline pycnocline Thermocline + Halocline = Pycnocline

  21. Sound in Water

  22. 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

  23. Speed of Sound (m/sec) 1,475 1,500 0 1000 2000 3000 4000 high speed min speed sofar layer Depth (m) high speed

  24. SOFAR Channel Distance 0 500 1000 1500 2000 sound rays Depth (m) SOFAR channel

  25. 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

  26. Dissolved Gasses in Seawater

  27. 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

  28. 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

  29. 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

  30. 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

  31. 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)

  32. Dissolved gasses in seawater: Seawater Air N2 48% 78% O2 36% 21% CO2 15% 0.04% Gasses dissolve most readily in cold water

  33. 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

  34. 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?

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