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Physical and Chemical Structure of the Ocean

Explore the reasons behind the blue color of the ocean, sound transmission in water, layers within the ocean, and more. Learn about the absorption of light and the effects of depth, as well as the properties of water. Understand how temperature and salinity variations impact the ocean's density and circulation. Discover the role of biology in nutrient cycles and the overall functioning of the ocean.

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Physical and Chemical Structure of the Ocean

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  1. Midterm #1 resultsposted early next weeksee BlackBoard Answer Keys for both White and Blue exams will be provided on course websiteScantrons will be returned in labs next week

  2. Physical and Chemical Structure of the Ocean Why are the oceans blue? How is sound transmitted in the ocean? Why is the ocean “layered” in many locations? How do you keep your beer cool in the tropics?

  3. Light Absorption in Water Intensity decreases rapidly with depthBlue and green penetrate deepest, giving the ocean its color

  4. Why do objects lose their color with depth? • The colors other than blue (and green) are absorbed by the water molecules in the first few meters -- only blue (and green) are reflected

  5. Sound in Sea Water • Sound is transmitted better in water than it is in air • Sound velocity in the ocean is about 1500 m/s, or about 4 times its speed in air • Sound velocity increases with pressure and temperature

  6. SOFAR Sound Channel • Sound is focused into the SOFAR channel because it is a low velocity region • Sound is transmitted best through this channel -- good for whales and submarines(e.g., “Hunt for Red October”)

  7. Heard Island Experiment Global Warming -- faster velocity?? Go to Sounds

  8. Ocean TemperatureSolar Heating • Uneven heating of Earth’s surface • Release of heat asinfrared radiation • Requires flow ofheat by oceans andatmosphere • Surface circulation

  9. Global Heat Budget • heatat the Earth's surface (342 W/m2) is supplied by absorption of ‘short-wave’ solar radiation from the sun. • heat lost from Earth is through long-wave radiation back to space.

  10. The Greenhouse Effect • The Atmosphere is transparent to sunlight (ultraviolet [UV] and visible) • Clouds absorb or reflect about half • Sunlight heats the Earth’s surface, which then radiates energy as longer wavelength energy (infrared) • This energy is trapped by the atmospheric gases (CO2, H2O, CH4)

  11. Special Properties of Water • RECALL:Melting and boiling points are very highHighest heat capacity of common liquidsHigh heat of fusion and vaporization

  12. Sea Surface Temperaturesonly 0°-30°C world-wide Land:50°C to -50°C

  13. Local Annual Heat Budgets • Amount of solar energy captured at one location on the Earth varies with season

  14. Local Annual Heat Budgets Where we live • Amount of solar energy captured at one location on the Earth varies with season

  15. Temperature (vertical profile) Seasonal changes in temperature profile

  16. Temperature (vertical profile) Thermocline Cool drinks go here

  17. Temperatures with Depth • Thermocline -- sharp temperature change

  18. Evaporation - Precipitation • Over the oceans, evaporation exceeds precipitation • The balance is restored by rain over the continents, returning water via rivers

  19. Evaporation vs Precipitation

  20. Climate Belts

  21. Ocean Surface Salinity

  22. Salinity Variations

  23. Salinity Variations • Surface salinity follows evaporation-precipitation pattern • Atlantic Ocean is generally more salty than Pacific Ocean, in spite of river input -- why??

  24. Isthmus of Panama • Net transfer offresh waterfrom Atlanticto Pacific

  25. Salinity of Rivers and Ocean Water Rivers Can’t just concentrate river water to get seawater How do we explain this observation? Ocean

  26. Concept of Residence Time Each element removed from ocean in different ways And at different rates e.g. Cl- vs. SiO2

  27. Residence Time Flux has units of mass per unit time Reservoir has units of mass R/F has units of time

  28. Density of Sea Water(Where does Oregon’s seawater plot?) o *

  29. Density of Sea Water(Where does Oregon’s seawater plot?) Oregon’s ocean o Bottom Water *

  30. Density Rules!

  31. Where does the Ocean’s Deepest Water Come From? • The densest seawater is COLD and SALTY • This is formed at high latitudes in the North and South Atlantic: North Atlantic Deep Water (NADW) Antarctic Bottom Water (AABW) • Could dense seawater form in the tropics? (evaporation!)

  32. Dissolved Gases in the Ocean

  33. Important Gases in the Ocean • Oxygen -- Respiration, Decomposition • CO2 -- Photosynthesis, CaCO3 • Nitrogen -- Nutrient for growth (NO3) • Methane -- a product of decomposition

  34. Photosynthesis and Respiration • Biology interacts with the Chemistry

  35. Dissolved Oxygen

  36. Biochemical Recycling

  37. Summary: Biochemical Cycles • Elements enter oceans through rivers • Gases enter oceans thru air-sea boundary • Biology alters distribution of elements (“nutrients”) and gases • Ocean circulates nutrients to surface, but only in a few places (called “upwelling”) • Interaction of physics, chemistry and biology => geological record (sediments)

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