Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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 • • • 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 Buoyancy Adaptation • Blubber • Swim bladder • Fatty liver • Buoyancy Compensator Device (BCD) Temperature Isotherms polar temperate 60o 30o 0o 30o tropic temperate polar Lines of equal temperature 60o Sea Surface Temperature July 2005 Properties of Light in the Ocean The Electromagnetic Radiation Spectrum Only green and blue wavelengths pass through water a great distance. 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 Wavelength (nm) 400 500 600 700 0m 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 Ocean • Spectral Characteristics – red wavelengths absorbed more readily by water than blue wavelengths – blue light penetrates deepest in the oceans 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 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. Density 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 64 lbs 64 lbs Water doesn’t change density under pressure Temperature Salinity Low High Low Density Low High High surface 0 m 100 m thermocline halocline pycnocline 1000 m Thermocline + Halocline = Pycnocline Sound in Water 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 source of noise Can hear many things such as ships miles away, shrimp eating, helicopters overhead, and whales communicating. Speed of Sound (m/sec) 1,475 1,500 0 high speed Depth (m) 1000 min speed 2000 3000 4000 high speed sofar layer SOFAR Channel Distance 0 Depth (m) 500 sound rays 1000 1500 2000 SOFAR channel 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 Dissolved Gasses in Seawater Solubility of Gases in Seawater as a Function of Temperature (salinity @ 33o/oo) Temperature (oC) 0 10 20 30 Solubility (ml/l at atmospheric pressure) N2 O2 CO2 . 14.47 11.59 9.65 8.26 8.14 6.42 5.26 4.41 8,700 8,030 7,350 6,660 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 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 The total pressure of a gas exerted by a mixture of gas is the sum of the gases exerted independently. Air N2 O2 CO2 H2O Total % 78.6 21.0 0.04 0.46 100 partial pressure (mm Hg) 597 159 0.3 3.7 760 Partial pressure is directly related to its % in the total gas mixture. E.g., at 1 atm PO2 = 159 mm Hg 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) Dissolved gasses in seawater: Seawater N2 48% O2 36% CO2 15% Air 78% 21% 0.04% Gasses dissolve most readily in cold water 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 1. What is isostacy? 2. Why do objects in water seen from the surface appear to bend? 3. Which gas is responsible for decompression sickness? 4. If a balloon is brought to 6 atm, what would it’s volume be? 5. Which wavelength of light penetrates the ocean the deepest?