1. Chapter 4 Water, Waves, and Tides

2. The “Weather” of the Marine Environment
Wind
Waves
Tides
Currents
Temperature
Salt

3. Waters of the Ocean
Where organisms are found in the marine environment is determined by the chemical and physical factors
To understand the biology of marine organisms, we must know something about the environment in which they live
Marine organisms are mostly made of water
80% or more by weight in most cases
Jellyfish – 95%
Water makes life possible

4. The Unique Nature of Pure Water
All matter is made of atoms
Elements – made of a single kind of element
Molecules – two or more atoms joined together – ex. Water
Water molecules stick together because of their polarity
These weak bonds are known as hydrogen bonds
Hydrogen bonds make water different from any other substance on earth

5. Three States of Matter Solid, liquid, gas
Water is the only substance that naturally occurs in all three states on earth

7. Heat and Water It takes a large amount of heat to melt ice
As heat energy is added and the temperature of ice rises, the molecules vibrate faster, breaking some of the hydrogen bonds that hold the crystal together
Latent heat
Melting
Amount of heat required to melt a substance
Evaporation
Amount of heat energy that is needed to evaporate a substance
Change from a liquid to a gas
Water absorbs a great deal of heat when it evaporates

8. Melting Ice
Once ice begins to melt added heat breaks more hydrogen bonds rather than increasing the speed of molecular motion
Any heat put in goes into melting the ice, not into raising the temperature

9. Heat Capacity
Amount of heat needed to raise a substance’s temperature by a given amount
How much heat a substance can absorb
Water has one of the highest heat capacities of any substance
Who cares?
Most marine organisms are not subjected to the rapid and sometimes drastic temperature changes that occur on land

10. Water as a Solvent Universal solvent
Especially good at dissolving salts
Salts are made of combinations of particles that have opposite electrical charges
The polarity of water allows it to break down the salts
Ion – electrically charged particles
Ions have stronger charges than the ends of water molecules
When a salt enters water the ions break apart and become surround by water molecules which break there hydrogen bonds to surround the ion
Ions pull apart or dissociate and the salt dissolves

12. Seawater
Characteristics of seawater are due both to the nature of the pure water and to the material dissolved in it
These come from the chemical weathering of rocks on land and are carried to the sea by rivers
Earth’s interior
Hydrothermal vents
Volcanoes

13. Salt Composition Solutes – dissolved materials
6 ions compose over 99% of the solids dissolved in seawater
Na and Cl account for 85% of the dissolved solids in seawater

14. Salinity 1 = dissolved trace elements
Total amount of salt dissolved in seawater
Usually expressed as the number of grams of salt left behind when 1,000 grams of seawater are evaporated (ppt)
Now use ppm =mg/L
Ions are good conductors of electricity
Electrical conductivity of seawater therefore reflects the concentration of dissolved ions
Practical Salinity Units – psu – measurement of salinity determined from conductivity measurements
1 = dissolved trace elements

15. Rule of Constant Proportions
Percentage of various ions in seawater remains constant even though the total amount of salt in the water can vary slightly
Oceans are chemically well mixed and ocean salinity varies almost entirely as a result of the addition or removal of pure water rather than the addition or removal of salt

16. Addition and Removal of Water
Water is removed from the ocean primarily by evaporation and to a lesser extent by freezing
Water is added to the ocean by precipitation

17. Average Salinity of the Ocean
35 ppt (parts per thousand)
Red Sea ppt
Baltic Sea 7 ppt (from river runoff)

18. Salinity, Temperature and Density
The saltier the water the denser it is
The density of seawater therefore depends on its temperature and its salinity

19. Measuring Temperature and Salinity
Can be measured by lowering specially designed bottles and thermometers on a wire to the desired depth
A weight called a messenger is released to slide down the wire, triggering the bottles to snap shut and trap a water sample

20. Temperature Profile
A graph that shows the temperature at different depths in the ocean
Water column – vertical shaft of water

22. Dissolved Gases
Gases are dissolved in seawater as well as solid materials
The 3 most important gases are: oxygen, carbon dioxide and nitrogen
Found in the atmosphere and dissolve at the sea surface (gas exchange)

23. Gas Exchange Gases dissolve better in cold than warm water
Dissolved gas concentrations are higher in polar waters than in the tropics

24. Oxygen Not very soluble 0 to 8 milliliters per liter of seawater
On average 4 to 6 ml/L
Air has 210 ml/L

25. Carbon Dioxide
More soluble than oxygen because it reacts chemically when it dissolves
80% of the dissolved gas in the ocean
.04% in air
Ocean is a sink for CO2
Stores more than 50 times as much total CO2 as the atmosphere

27. Transparency Biologically important property
Sunlight can penetrate into the ocean
Allows for photosynthesis
Not all colors penetrate seawater equally well
Water is most transparent to blue light
As depth increases more colors are filtered out
Red is the first to be filtered out
Something that is red at the surface looks black or gray at depth because there is no red light to reflect off them and be seen
At depths of 1000 m or 3300 ft there is total darkness

29. Turbidity
Transparency of water is strongly affected by material that is suspended and dissolved in the water
Ex. Muddy water, lots of plankton

30. Pressure Factor that changes dramatically with depth
On land – 1 atm of pressure
With each 10m (33-35 ft) of increased depth another atmosphere of pressure is added
As the pressure increases the gases are compressed – limits range of organisms
ex. Swim bladder

31. Density
Much of the three dimensional structure of the sea, especially in relation to depth is controlled by the density of the water
Densest water sinks so the ocean is usually layered or stratified
Deep water – cold and dense
Surface water – warm and light

32. Water Column Stability
Stable Water Column - Less dense on top, dense on bottom
Low stability – surface water is only slightly less dense
Highly stable – large density difference
Unstable – surface water more dense than bottom water
Downwelling – when surface water sinks
Overturn – when dense surface water displaces deeper water
Overturn usually occurs in temperate and polar regions during the winter when the surface water cools
The water descends to a depth determined by its density
Temperature and density profiles are vertical straight lines for water columns experiencing overturn
The processes that change salinity in the open ocean (precipitation, evaporation and freezing) occur only at the surface
Temperature changes occur only at the surface

34. Water Mass Once surface water has sunk its properties do not change
The volume of water has a “fingerprint”, a characteristic combination of temperature and salinity
Oceanographers can tract the movement or circulation of water masses

35. Thermohaline Circulation
Circulation driven by changes in density which in turn is determined by temperature and salinity
Extend throughout the ocean depths
Important in regulating earth’s climate and chemically mixing the oceans
Brings dissolved oxygen to the deep sea
Helps determine the abundance of life in the deep sea

37. Video Notes

38. Surface Layer 100 to 200 m thick (330 to 660 ft)
Mixed by wind, waves and currents
Also known as the mixed layer
Thermocline
Sudden changes in temperature over small depth intervals
seasonal

39. Intermediate Layer Below the surface layer of around 1500 m (5000 ft)
Contains the main thermocline
zone of transition between warm surface water and cold water below
lies in the intermediate layer
rarely breaks down
feature of the open ocean

40. Deep and bottom layers Below 1,500 m or (5,000 ft) Uniformly cold
Typically less than 4oC (39 oF)

41. Surface Circulation
Most intense motion of the ocean occurs at the surface in the form of surface currents and waves
Driven by wind which is driven by heat from the sun
Coriolis effect also strongly influences

43. Coriolis Effect
Earth is round and rotating so anything that moves over its surface tends to turn a little rather than moving in a single straight line
Mostly effects winds and ocean currents that move over large distances

44. Northern Hemisphere – deflects things to the right
Southern Hemisphere – deflects things to the left

45. Winds Patterns
Winds in our atmosphere are driven by heat energy from the sun
Most of the solar energy is absorbed near the equator
Warm air rises at the equator
Air from adjacent areas gets sucked in to replace the rising equatorial air creating wind
The wind does not move straight to the equator but are bent by the Coriolis effect – approach at a 45 angle

46. Winds Trade winds winds near the equator (northeast and the southeast)
steadiest winds on earth
between 0 and 30 degrees
Westerlies
driven by solar energy
more variable
between 30 and 60 degrees
move in the opposite direction to the trade winds
Polar easterlies
Most variable
Between 60 and 90 degrees

48. Surface Currents
The major wind fields of the atmosphere push the sea surface creating currents
All major surface currents of the open ocean are driven by the wind
When pushed by the wind the uppermost layer of water begins to move
The water does not move in the same direction as the wind but at a 45o angle because of the Coriolis effect
The top layer pushes the water below but at a 45o angle and so on

49. Ekman Spiral
Spiral change in the movement in the water column when the water is pushed by the wind
At a depth of a few hundred meters the wind is not felt at all
Ekman Layer – upper part of the water column that is affected by the wind

50. Ekman transport – taken as a whole the Ekman layer moves at 90o from the wind direction

51. Consequence of the Coriolis Effect
Trade winds move towards the equator the equatorial currents that these winds produce move parallel to the equator

52. Gyres
Wind driven surface currents combined into huge more less circular systems
Under the influence of the Coriolis Effect

53. Transportation of Solar Heat
Warm currents on the western sides of the gyres carry vast amounts of solar heat from the equator to higher latitudes
Cold currents flow in opposite direction on the eastern sides
Ocean currents act as a giant thermostat warming the poles and cooling the tropics

55. El Nino and La Nina
Large scale fluctuations in current patterns that can have a dramatic impact on weather around the world
El Niño and La Niña are the warm and cool phases of a recurring climate pattern across the tropical Pacific—the El Niño-Southern Oscillation, or “ENSO” for short.
The pattern can shift back and forth irregularly every two to seven years, and each phase triggers predictable disruptions of temperature, precipitation, and winds.
These changes disrupt the large-scale air movements in the tropics, triggering a cascade of global side effects.

56. Role of Surface Currents
Surface water temperatures are higher on the western sides of the oceans where currents carry warm water away from the equator

57. Waves Caused by winds Most familiar of all ocean phenomena
Affect the organisms that live on the shore
Parts
Crest – highest part of a wave
Trough – lowest part of a wave
Wave Height – vertical distance between trough and crest
Wavelength – distance between two successive crests or troughs
Period – time a waves takes to go by any given point

59. Water Movement In a wave crest, water moves up and forward
In a wave trough, water moves down and back
On the whole water particles do not go anywhere at all – just move in circles
Waves carry energy across the surface, not water

61. Formation of waves Begins when the wind starts to blow
The faster and longer the wind blows the larger the waves get
Fetch – span of open water over which the wind blows and it determines size of waves

63. Types of waves Seas Swells
waves that have sharp peaks and relatively flat wave troughs
Swells
Waves with smooth rounded crests and troughs
Similar to ideal waves

64. Surf
Waves that becomes so high and steep as it approaches the shoreline that it breaks
Waves become closer together
Energy is released on the shoreline when the wave breaks

65. Tsunamis Deadly waves Japanese word for “harbor wave”
Produced by earthquakes, landslides, volcanoes, and other disturbances of the sea floor
Tidal waves – properly called – seismic sea waves
Long fast moving waves
Wavelengths of 240 km (150 mi)
Travel 700 km/hr (435 mi/hr) – as fast as a jet plane
Open ocean – not very high – 1 m

66. Warning
Worldwide network of seismic monitoring stations that provide instant notice of an earthquake or other seismic disturbance
System has saved lives but is far from perfect
Can’t predict which earthquakes produce killer tsunamis
Also many people in developing countries do not get the warnings

67. Tides Dominant influence on near shore sea life
Expose and submerge organisms on the shore
Drive the circulation of bays and estuaries
Triggers spawning
Caused by the gravitational pull of the moon and sun by rotations of the earth moon and sun
Earth and the moon rotate around a common point (their combined center of mass)
This rotation produces a centrifugal force

68. Centrifugal Force
Earth and the moon rotate around a common point (their combined center of mass)
This rotation produces a centrifugal force
The centrifugal force just balances the gravitational attraction between earth and the moon
The centrifugal force and the moon’s gravity are not in perfect balance everywhere on earth’s surface
On the side nearest the moon, the moon’s gravity is stronger and pulls the water toward the moon
On the side away from the moon the centrifugal force dominates and pushes the water away from the moon
If earth were completely covered with water, the water would form two bulges on opposite sides of the planet
Water would be deep under the bulges and shallower away from the bulges

69. Centrifugal Force and Tides
Earth is spinning like a top on its own axis
As it does this any given point would be under the bulge and then away from the bulge
High tide occurs when a point is under a bulge and low tide occurs when it is away from a bulge
The earth rotates on its axis every 24 hours so a point will have two high tides and two low tides
The moon advances on it orbit each day so a full tidal cycle takes 24 hours and 50 minutes

71. The Sun’s Bulge Sun produces a bulge like the moon but is it smaller
When the sun and the moon are in line there bulges add up and when they are at right angle to one another they cancel each other out

72. Tidal Range
Difference in water level between successive high and low tides

73. Spring Tide When the sun and moon bulge add together
High high tides and low low tides
Named because they seem to surge up like spring water
Occur when there is a full or new moon

74. Neap Tide Occur when sun and moon are at right angles to one another
Moon is in the 1st and 3rd quarters
Average tides
Low high tide and a high low tide

76. Variations in Tides
Tides vary from place to place depending on the location and on the shape and depth of the basin

77. Bay of Fundy, Canada

78. Tide Terms Semidiurnal tides – two high and two low tides
Mixed semidiurnal tides- successive high tides of different height
Diurnal Tides – one high and one low - uncommon

79. Tide Tables Give the predicted time and height of high and low tides
Very accurate