1. Chapter 4
Water, Waves, and Tides

2. 71% of Earths surface is covered with water
97% salt water
3% fresh water

3. Nature of Water Marine organisms are 70 – 80% water by mass.
Terrestrial organisms are approximately 66% water by mass!
Physical properties of water
excellent solvent
high boiling point and freezing point
denser in its liquid form than in its solid form
supports marine organisms through buoyancy
provides a medium for chemical reactions necessary for life

4. Nature of Water Structure of a water molecule
2 H atoms bonded to 1 O atom
polar - different parts of the molecule have different electrical charges:
the oxygen atom carries a slight negative charge; the hydrogen atoms carry a slight positive charge

5. Figure 4-1 (a) Water Molecules.

6. Figure 4-1 (b) Water Molecules.

7. Figure 4-1 (c) Water Molecules.

8. Nature of Water Specific heat (Thermal capacity) Water and light
ocean can maintain relatively constant temperature
Water and light
much light reflected into the atmosphere
different wavelengths (colors) of light penetrate to different depths

9. Nature of Water Chemical properties of water
pH scale measures acidity/alkalinity
ocean’s pH is slightly alkaline (average 8)
organisms’ internal and external pH affect life processes such as metabolism and growth

10. Salt Water Salinity seawater = 3.5% salt, 96.5% water
expressed as in g per kg water or parts per thousand (ppt)
salinity of surface water varies as a result of evaporation, precipitation, freezing, thawing, and freshwater runoff from land
areas around 30o N and 30o S = high salinity (evaporation > precipitation)
poles = high salinity (freezing – removes water from sea)

11. Hydrogen sulfide (H2S) Chlorine (Cl2) Sulfur Chloride (Cl–)
Precipitation
Chloride (Cl–)
Sulfate (SO42–)
Hydrogen sulfide (H2S)
Chlorine (Cl2)
Volcano
Sulfur
Sea spray
removes salts
Salts removed
when organisms are
caught for food
River
discharge
Carbonate (CO32–)
Calcium (Ca2+)
Sulfate (SO42–)
Sodium (Na+)
Magnesium (Mg2+)
Calcium (Ca2+)
Magnesium (Mg2+)
Potassium (K+)
Rock on
the seafloor
Clay particles
adsorb
Organisms
die
Bottom sediments
Precipitation
Stepped Art
Fig. 4-6, p. 75

12. Salt Water Gases in seawater gases from biological processes
oxygen is a by-product of photosynthesis
release of CO2 from respiration
oxygen-minimum zone – located just below sunlit surface waters
solubility of gases in seawater
seawater has more O and CO2 but less N than the atmosphere
affected by temperature, salinity and pressure

13. Table 4-3 Gases Found in Seawater

14. Figure 4-8 Distribution of Solar Energy.

15. Ocean Heating and Cooling
Sea temperature
temperature varies daily and seasonally
affected by energy absorption at the surface, loss by evaporation, transfer by currents, warming/cooling of atmosphere, heat loss through radiation
seasonal variations in the amount of solar radiation reaching the earth, occur especially between 40o and 60o N and S because angle of sun’s rays change dramatically at these latitudes seasonally

16. Figure 4-10 Average Surface Temperatures Of The World Ocean.

17. Winds and Currents Winds
result from horizontal air movements caused by temperature, density, etc.
as air heats, its density decreases and it rises; as it cools, density increases and it falls toward earth
wind patterns: upper air flow from the equator towards the north and south

18. Figure 4-11 North-South Air Flow.

19. Winds and Currents Winds Coriolis effect
Apparent force on moving particles resulting from the earth’s rotation
path of air mass appears to curve relative to the earth’s surface—to the right in the Northern Hemisphere, left in the Southern

20. Figure 4-12 (c) The Coriolis Effect.

21. Winds and Currents Surface wind patterns
3 convection cells in each hemisphere:
northeast & southeast trade winds
westerlies
polar easterlies
areas of vertical air movement between wind belts
Doldrums (at equator)
horse latitudes (at 30o N & S)

22. Figure 4-13 Surface Wind Patterns.

23. Winds and Currents Ocean currents surface currents
driven mainly by trade winds (easterlies and westerlies) in each hemisphere
Coriolis effect
deflection can be as much as 45-degree angle from wind direction
gyres—water flow in a circular pattern around the edge of an ocean basin

24. Figure 4-14 (a) Gyres.

25. Figure 4-14 (b) Gyres.

26. Winds and Currents Classification of currents
western-boundary currents: fastest, deepest currents that move warm water toward the poles in each gyre (e.g. Gulf Stream)
eastern-boundary currents: slow moving, carry cold water toward the equator
transverse currents: connect eastern- and western-boundary currents in each gyre
biological impact
western-boundary currents not productive, carry little nutrients, but increase oxygen mixed in water
eastern-boundary currents productive, nutrient-rich

27. Figure 4-15 Major Ocean Currents.

28. Winds and Currents Currents below the surface
energy transferred from winds to surface water is transferred to deeper water
deeper-water currents are deflected by the Coriolis effect, down to about 100 m
friction causes loss of energy, so each layer moves at an angle to and more slowly than the layer above, creating an Ekman spiral
Ekman transport—net movement of water to the 100-m depth

29. Figure 4-16 Ekman Spiral.

30. Ocean Layers and Ocean Mixing
Density increases when salinity increases
Density increases when temperature decreases

31. Ocean Layers and Ocean Mixing
Characteristics of ocean layers
depth m (330 feet): warmed by solar radiation, well mixed
100-1,000 m: temperature decreases
thermocline – zone of rapid temperature change
halocline: salinity increases 0-1,000 m
pycnocline: 100-1,000 m, where changes in temperature and salinity create rapid increases in density
seasonal thermoclines

32. Figure 4-18 (a) Changes In Temperature, Salinity, And Density Of Seawater With Depth.

33. Figure 4-18 (b) Changes In Temperature, Salinity, And Density Of Seawater With Depth.

34. Figure 4-18 (c) Changes In Temperature, Salinity, And Density Of Seawater With Depth.

35. Ocean Layers and Ocean Mixing
Horizontal mixing
winter temperatures and increased salinity owing to freezing result in very dense water at the poles, which sinks toward the ocean floor

36. Ocean Layers and Ocean Mixing
Vertical mixing
isopycnal—stable water column that has the same density from top to bottom
vertical mixing allows water exchange between surface and deep waters
nutrient-rich bottom water is exchanged for oxygen-rich surface water

37. Ocean Layers and Ocean Mixing
Upwelling and downwelling
equatorial upwelling
water from currents on either side of the equator is deflected toward the poles, pulling surface water away to be replaced by deeper, nutrient-rich water
coastal upwelling
Ekman transport moves water offshore, to be replaced by deeper, nutrient-rich water
coastal downwelling
coastal winds force oxygen-rich surface waters downward and along the continental shelf

38. Ocean Layers and Ocean Mixing
Deepwater circulation
differences in density, not wind energy, cause water movement in deep oceans
dense Antarctic water sinks to the bottom and moves slowly toward the Arctic

39. Waves
Wave formation
wave: a flow of energy or motion, not a flow of water
generating force: a force that disturbs the water’s surface, e.g., wind, geological events, falling objects, ships

40. Figure 4-22 Characteristics Of Waves.

41. Waves
Types of waves
Progressive (forced) waves are generated by wind and restored by gravity, progress in a particular direction
forced waves are formed by storms, which determine their size and speed
free waves, no longer affected by the generating force, move at speeds determined by the wave’s length and period
swells are long-period, uniform free waves which carry considerable energy and can travel for thousands of km

42. Waves Types of Waves (con’t) deepwater and shallow-water waves
deepwater waves—waves that occur in water that is deeper than ½ of a wave’s wavelength
breakers
deepwater waves become shallow-water waves when they move into shallow water
surf zone—area along a coast where waves slow down, become steeper, break, and disappear
breakers form when the wave’s bottom slows but its crest continues at a faster speed

43. Figure 4-23 Breakers.

44. Waves Types of Waves (con’t) Tsunamis (large seismic sea waves)
seismic sea waves are formed by earthquakes
tsunamis have long wavelengths, long periods and low height
compression of the wave’s energy into a smaller volume upon approaching a coast or island causes a dramatic increase in height

45. Figure 4-24 Tsunami.

46. Tides
Tides: periodic changes in water level occurring along coastlines
Why tides occur
tides result from the gravitational pull of the moon and the sun
though smaller, the moon is closer to earth, so its gravitational pull is greater
water moves toward the moon, forming a bulge at the point directly under it
the centrifugal force opposite the moon forms another bulge
areas of low water form between bulges

47. Figure 4-25 Tides.

48. Tides Spring and neap tides
during spring tides, the times of highest and lowest tides, the earth, moon and sun are in a line and act together creating highest and lowest tides
when the sun and moon are at right angles, the sun’s pull offsets the moon’s, resulting in neap tides, which have the smallest change between high and low tide

49. Figure 4-26 Spring And Neap Tides.

50. Tides
Tidal range
diurnal tide: one high tide and one low tide each day
semidiurnal tide: two high tides and two low tides each day (most common)
mixed semidiurnal tide: high and low tides are at different levels
flood tides are rising; ebb tides are falling
tidal currents are associated with tidal cycle
slack water occurs during the change of tides

51. Figure 4-27 (a, b & c) Tidal Patterns.

52. Figure 4-27 (d) Tidal Patterns.

53. Climate and the Ocean Ocean is a great modifier of temperature
Hydrologic cycle
Convection, evaporation, and precipitation

54. Weather Front - when cold air mass collides with a warm air mass
Fronts are marked by stormy weather

55. Monsoons
Seasonal wind pattern changes caused by heating or cooling on the continents
Summers - significant rainfall and winters - very little
Common on the west coast of India and in Southeast Asia

56. Cyclones
Large rotating storm systems of low-pressure air Forms over warm oceans near Equator
Typhoons – Pacific Ocean
Hurricanes – Atlantic Ocean
Strong rotating winds
At least 74 miles per hour
Thunder and Lightning
Winds rotate in a counterclockwise direction around a central, calm eye

57. When it moves over land (or cold water) the storm begins to weaken quickly
Storm is fueled by warm water
Average 100 cyclones worldwide each year

58. Weather symbol for a hurricane is:
Marine flags that warn of a hurricane

59. Hurricane Structure Eye – relatively calm roughly 20 to 30 miles wide
Smaller the eye – stronger the winds
Right side generally has the fastest winds
Left side usually has the most rain

60. Hurricane Classification
5 categories based on current maximum wind speed
Saffir-Simpson Hurricane Scale
Category 1 – Winds mph
Category 2 – Winds mph
Category 3 – Winds mph
Category 4 – Winds mph
Category 5 – Winds over 155 mph
Very rare, status for a short time

61. Storm Surges
Becoming more dangerous due to increase in coastal population

62. Waterspouts Tornado over water May carry water as high as 328 ft
Very short-lived
Not particularly dangerous
Most often occur during the summer months
Florida Keys have the most in the U.S.