1. Class 15 -- The Oceans PROPERTIES OF SEA WATER Salinity
Effect of salinity on physical properties
ENERGY TRANSMISSION/ABSORPTION IN WATER AND SEA WATER
Heat
Light

2. SEA WATER (= Ocean water):
Salinity - - amt. of dissolved salts; symbol = S
Average S = 35 g/kg (p.p.t., ‰)
Range (most sea water): ‰
How does sea water differ from fresh water?
Greater S --> greater density
Dissolved salts change water properties…
Boiling point higher = 103˚C
Freezing point lowered...

3. Freezing of sea water: 1- salt exclusion
-- Begins to freeze at -2˚C
-- Salt is excluded from the ice that is formed.
-- Remaining water saltier, so...
-- This water freezes at lower temp.
-- As seawater cools below 4˚C, density increases
Very important: This means that the coldest sea water sinks to the bottom.
Oceans not stratified like lakes in winter

4. Density of sea water just above
the freezing point
-- As seawater cools below 4˚C, density increases
Unlike fresh water lakes
Very important: This means that the coldest sea water sinks to the bottom.
This creates deep currents (more later)

6. Density of seawater-
... Higher S water is denser
... Colder water is denser
Very important! Remember convection:
Dense water at ocean surface SINKS in places where water is
coldest and/or
salinity is highest, caused by
freezing
evaporation
“Deep water” currents come from these areas

9. How deep does sunlight penetrate into the oceans?
Why is the ocean blue?
How deep does sunlight penetrate into the oceans?
How does solar energy get absorbed by the ocean?

10. Sunlight energy transmission and absorption
by water
Radiant energy = Radiation -- direct transmission, through space, air, water, etc.
Different wavelength (l) waves are different colors of light, different types of radiant energy
Solar energy- many l’s combined

11. Fig. 13.3

12. Absorption of solar radiation
by the oceans
Sun’s rays reaching the sea surface:
visible
infrared = heat
ultraviolet
Absorption by ocean water is strong, but depends on wavelength...

14. How much energy or light is absorbed at various depths?
What kind of energy or light is absorbed at various depths?

18. Consequences: Photosynthesis <150 meters
Heating from sun only affects top several meters
Blue color of sea water: only shorter wavelengths at depth

19. Photosynthesis limited to top <150 m

20. Water vapor = “latent” heat

21. Heat
Within The Oceans

22. heat energy transfer between touching substances: warm to cool
Conduction --
heat energy transfer between touching substances: warm to cool
Surface of the ocean <--> atmosphere
conduction important
BUT only affects the top few meters
Conduction between surface of ocean and deep water – not much
Water is a poor heat conductor over long distances
Example: Water at 1000m depth near Bahamas is barely above freezing!

23. Warm Climate Zones: Warm surface layer+ cold water below Stratification

24. Convection Heat or “coldness” moves with density-driven currents
Convection very important in the atmosphere and the oceans
Atmosphere- Heated at bottom, cooled at top
Cooling
Heating

25. Convection in the Oceans-
Cooling of surface water in far north, far south
Warming of surface water at low latitude
Cooling
Heating
North Atlantic
Equator