Lecture 1. Course Introduction

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Lecture 1. Course Introduction Powered By Docstoc
					       Physical and Chemical
      Structure of the Ocean

         Why are the oceans blue?
   How is sound transmitted in the ocean?
How do you keep your beer cool in the tropics?
Light Absorption in Water
             Intensity decreases
             rapidly with depth
             Blue and green
             penetrate deepest,
             giving the ocean its
             color
  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
      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 increase with pressure and
temperature
    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
 Heard Island Experiment
Global Warming -- faster velocity??




                           Go to Sounds
Solar Heating
Uneven heating of
 Earth‟s surface
Release of heat as
 infrared radiation
Requires flow of
 heat by oceans and
 atmosphere
           Global Heat Budget
 heat at 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.
    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)
Special Properties of Water
RECALL:
 Melting and boiling points are very high
 Highest heat capacity of common liquids
 High heat of fusion and vaporization
Sea Surface Temperatures
only 0°-30°C world-wide
                  Land:
                  50°C to -
                  50°C
 Local Annual Heat Budgets




 Amount of solar energy captured at one location
  on the Earth varies with season
Temperature (vertical profile)
Temperature (vertical profile)



                      Beer goes here
   Temperatures with Depth
Thermocline -- sharp temperature
 change
 Evaporation - Precipitation
Over the oceans, evaporation exceeds
 precipitation
The balance is restored by rain over
 the continents, returning water via
 rivers
Evaporation vs Precipitation
Climate Belts
Ocean Surface Salinity
Salinity Variations
Chemistry of River and Ocean Water


Can’t just concentrate
                         Rivers
river water to get
seawater

How do we explain this
observation?             Ocean
 Concept of Residence Time

Each element removed
from ocean in different
ways

And at different rates

e.g. Cl- vs. SiO2
Residence Time
                 Flux has units of mass
                 per unit time

                 Reservoir has units of
                 mass

                 R/F has units of time
       Salinity Variations
Surface salinity follows evaporation-
 precipitation pattern
Atlantic Ocean is generally more salty
 than Pacific Ocean, in spite of river input
 -- why??
        Isthmus of Panama
Net transfer of
 fresh water
 from Atlantic
 to Pacific
   Density of Sea Water
(Where does Oregon‟s seawater plot?)
   Density of Sea Water
(Where does Oregon‟s seawater plot?)


                              Oregon’s ocean


                              Bottom Water
Density Rules!
   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!)
Dissolved Gases in the Ocean
Important Gases in the Ocean

Oxygen -- Respiration, Decomposition
CO2 -- Photosynthesis, CaCO3
Nitrogen -- Nutrient for growth
Methane -- a product of decomposition
Photosynthesis and Respiration

 Biology interacts with the Chemistry
Dissolved Oxygen
Biochemical Recycling
  Summary: Biochemical Cycles
Nutrients enter oceans through rivers
Gases enter oceans thru air-sea boundary
Biology alters distribution of nutrients and
 gases
Circulation returns nutrients to surface,
 but only in a few places (called “upwelling”)
Interaction of physics, chemistry and
 biology => geological record (sediments)

				
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