chapter 3 chemical and physical features of seawater and world oceans
TRANSCRIPT
Chapter 3
CHEMICAL AND PHYSICAL FEATURES OF SEAWATER AND
WORLD OCEANShttp://www.learner.org/vod/vod_window.html?pid=804
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
All matter is made of atoms Elements are make from one kind of atom
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
A molecule is two or more different atoms combined Example: water
Water is a polar molecule ; one end is positively charged and the other is negatively charged
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
The Three States of Water Only substance on Earth to naturally exist in
three states or phases . Weak hydrogen bonds form between to the
positive end and the negative end of different water molecules
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
The Three States of Water Hydrogen Bonds
Sank the Titanic The Titanic sank because it hit an iceberg - a chunk of ice
floating on the surface of the ocean. The reason ice floats is because of hydrogen bonding.
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
The Three States of Water Hydrogen Bonds
Associated with Basilisk Lizard (Jesus Lizard) http://www.youtube.com/watch?v=45yabrnryXk&edufilter=DQBPVNZ5nlfNZmzO0OgIrQ
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
The Three States of Water Weak hydrogen bonds form between to the
positive end and the negative end of different water molecules Liquid
http://www.visionlearning.com/library/flash_viewer.php?oid=1380&mid=57
Solid http://www.visionlearning.com/library/flash_viewer.php?oi
d=1381&mid=57
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
The Three States of Water
Solid
Gas Liquid
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
The Three States of Water Solid water molecules pack close together &
locked in fixed three dimensional pattern Becomes more dense until about 4°C
(get less dense) & expands When water freezes in fresh and marine
water the ice forms on top allowing organisms to live underneath the ice
When marine water freezes it acts like an insulator to stop freezing all the water
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
Heat and Water Bonds must be broken before molecules can
begin to move around Melts at higher temperature & absorbs a
lot of heat when it melts (high latent heat of melting) and great deal of heat must be removed to freeze it
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
Heat and Water Melting ice, added heat breaks more hydrogen
bonds than increasing molecular motion Mixture of ice & water is 0°-adding heat
goes into melting the ice not raising temperature
High heat capacity -marine organisms not affect by temperature changes in atmosphere & latent heat of evaporation
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
Water as a Solvent Dissolve more things than any other natural
substance (universal solvent) especially salts Salts made of opposite charged particles and
conducts electricity Single atoms or groups of atoms
In water, strong ion charges attract water molecule, water molecules surround the ions and pull them apart (dissociation)
3.1 THE WATERS OF THE OCEANThe Unique Nature of Pure Water
Water as a Solvent In water, strong ion charges attract water
molecule, water molecules surround the ions and pull them apart (dissociation)
3.1 THE WATERS OF THE OCEANSeawater
Characteristics due to nature of pure water & materials dissolved in it
Dissolved solids due to chemical weathering of rocks on land & hydrothermal vents
3.1 THE WATERS OF THE OCEANSeawater
Salt Composition Sodium chloride account for 85% of all solids
dissolved Salinity is total salt dissolved in seawater
Number of grams left behind when 1000 grams evaporated
If 35 grams left then 35 parts per thousand or 350/00 or 35 psu (practical salinity units)
3.1 THE WATERS OF THE OCEANSeawater
Salt Composition Rule of constant proportions states that the
relative amounts of various ions in seawater are always the same
Differences in salinity results from removal (evaporation) and addition (precipitation) of water
Rarely have to deal with changes in ratio of ions as result easier to control salt & water balance
3.1 THE WATERS OF THE OCEANSeawater
Salt Composition Average salinity is 35 psu and between 33-37
psu in open ocean Dead Seahttp://www.youtube.com/watch?v=tzBJy6BXf5Y&edufilter=DQBPVNZ5nlfNZmzO0OgIrQ
3.1 THE WATERS OF THE OCEANSeawater
Salt Composition Red Sea is 40 psu Baltic Sea is 7 psu
Why is Red Sea salinity so high and the Baltic Sea so low?
3.1 THE WATERS OF THE OCEANSeawater
Salinity, Temperature, and Density Density – mass per unit volume (D=m/v) Get denser as it gets saltier, colder, or both -2° to 30°C
temps. below zero possible because saltwater freezes at colder temps.
3.1 THE WATERS OF THE OCEANSeawater
Salinity, Temperature, and Density Density controlled more by temperature than
salinity There are exceptions therefore salinity &
temp need to be measured to determine density
3.1 THE WATERS OF THE OCEANSeawater
Dissolved Gases O
2, CO
2 and N
2 in atmosphere & sea surface
Gas exchange happens between the surface & atmosphere
Dissolved gas concentration higher in cold water, lower in warm water
3.1 THE WATERS OF THE OCEANSeawater
Dissolved Gases Amount of oxygen in water is affected by
photosynthesis & respiration Most oxygen is released into the atmosphere
More susceptible to oxygen depletion than atmosphere
80% of gases is carbon dioxide
3.1 THE WATERS OF THE OCEANSeawater
Transparency Sunlight can penetrate, but it’s affected by the
material suspended in the water Important to the photosynthetic organisms Runoff makes coastal waters less transparent
than deep blue waters of open ocean
3.1 THE WATERS OF THE OCEANSeawater
Pressure 压力
• On land, organisms are under 1 atm at sea level
Marine organism have the pressure of the atmosphere & water
3.1 THE WATERS OF THE OCEANSeawater
Pressure With every 10m increase depth another atm is
added
3.1 THE WATERS OF THE OCEANSeawater
Pressure As atms increase gases are compressed
Organism have air bladders, floats and lungs that shrink and collapse
Limits depth range, some organism are injured when brought to the surface
Submarines & housing must be specially engineered to withstand pressure
3.2 OCEAN CIRCULATION
• http://www.youtube.com/watch?v=CCmTY0PKGDs&edufilter=DQBPVNZ5nlfNZmzO0OgIrQ
3.2 OCEAN CIRCULATION
Throughout depths of ocean are currents
• Move and mix oceans waters
• Transport heat, pollutants and organisms
3.2 OCEAN CIRCULATIONSurface Circulation
Driven by the wind
• Wind is driven by heat from sun
• Winds and currents influenced by Coriolis effect.
3.2 OCEAN CIRCULATIONSurface Circulation
The Coriolis Effect
• Because Earth is rotating anything that moves over the surface tends to turn a little rather in a straight line
• Deflects large-scale motions like winds and currents to the right in Northern Hemisphere and to the left in Southern Hemisphere.
3.2 OCEAN CIRCULATIONSurface Circulation
Wind Patterns•Winds driven by heat energy from sun
3.2 OCEAN CIRCULATIONSurface Circulation
Wind PatternsTrade winds -warmer at equator
• Wind at equator becomes less dense and air from
• Adjacent areas gets sucked in to replace it creating winds
• Wind bent by Coriolis Effect• Approach equator at 45° angle where there
is no land• Steadiest winds
3.2 OCEAN CIRCULATIONSurface Circulation
Wind Patterns•Westerlies at middle latitudes move in opposite direction
•Polar easterliesat high latitudesmost variablewinds
3.2 OCEAN CIRCULATIONSurface Circulation
Surface Currents
Direction of wind currents
3.2 OCEAN CIRCULATIONSurface Circulation
Surface Currents
Produce Ekman transport upper part of water column moves
perpendicular (90o) to wind direction to right N. Hemisphere & left in S. Hemisphere
3.2 OCEAN CIRCULATIONSurface Circulation
Surface Currents•Global wind patterns and the Coriolis effect produce gyres (+sun’s heat & gravity)
•Gyres large circular systems of ocean currents
3.2 OCEAN CIRCULATIONSurface Circulation
Surface Currents•West side of gyres carry warm water to higher latitudes while cold current flow on eastern sides
3.2 OCEAN CIRCULATIONSurface Circulation
Surface Currents•West side of gyres carry warm water to higher latitudes while cold current flow on eastern sides
3.2 OCEAN CIRCULATIONSurface Circulation
Surface CurrentsWest side - warm water East side – cold
• Giant thermostat warming the poles & cooling tropics
• Tropical organisms like corals tend to extend into high latitudes on the west sides of the oceans
• Cold loving organisms like kelp grow closest to equator on eastern shores
3.2 OCEAN CIRCULATIONSurface Circulation
Surface CurrentsEl Niño
•Pacific Ocean
•Southeast trade winds slacken or cease
•Cool, nutrient-rich water within the Peru Current prevented from moving up to replace warm surface water
3.2 OCEAN CIRCULATIONSurface Circulation
Surface CurrentsEl Niño
•No nutrient-rich water = no plankton, a major source of food for fish, dies off
•Major disruption of the ecosystem
•Also alters jet stream path in the Northern Hemisphere
• Causes unusual increase in precipitation.
3.2 OCEAN CIRCULATIONSurface Circulation
Surface CurrentsEl Niño
•Occurs about 14 times in a century
•Named El Niño (“the Child,” referring to the baby Jesus) because it usually begins around Christmas.
3.2 OCEAN CIRCULATIONThermohaline Circulation and the
Great Ocean Conveyor
•Ocean water stratified• Cold more dense on the bottom &
warmer less dense on top
3.2 OCEAN CIRCULATIONThermohaline Circulation and the
Great Ocean ConveyorThe Three-layered Ocean0Surface layer or mixed layer
• 100 to 200m thick
• Mixed by wind, waves and currents
• Sometimes in summer & spring in temperate & polar waters sharp transition to cooler water (thermoclines)noticed by divers
3.2 OCEAN CIRCULATIONThermohaline Circulation and the
Great Ocean Conveyor
The Three-layered Ocean•Intermediate layer/ 中间层 depth of 1000 to 1500m
• Main thermocline rarely breaks down & in open ocean
3.2 OCEAN CIRCULATIONThermohaline Circulation and the
Great Ocean Conveyor
The Three-layered Ocean•Deep or bottom layers/ 深或底层
• Below 1500 m• typically less than 4°C
3.2 OCEAN CIRCULATIONThermohaline Circulation and the
Great Ocean Conveyor
•Upwelling 上涌 occurs where Ekman transport moves surface waters away from the coast; surface waters are replaced by water that wells up from below.
•Where Ekman transport moves surface waters toward the coast, the water piles up and sinks in the process known as coastal downwelling下行 .
3.2 OCEAN CIRCULATIONThermohaline Circulation and the
Great Ocean Conveyor
The global ocean conveyor belt is a constantly moving system of deep-ocean circulation driven by temperature and salinity
3.3 WAVES AND TIDESWaves Caused by wind Parts of a wave: crest, trough, wavelength (,
wave height, amplitude
3.3 WAVES AND TIDESWaves
Waves
3.3 WAVES AND TIDESWaves
Waves Wave crest moves up & forward Trough moves down and back Water particles do not go anywhere
Moves in a circle
ADD TO REVIEW GUIDE
26. Why do surfers like to go surfing after a big offshore storm?
27. What is the difference between sea, swell, and surf?
28. What causes tides?
29. What causes spring tides and neap tides.
30. Describe the varying types of tides that occur within a 24 hour period.
3.3 WAVES AND TIDESWaves
Waves Fetch -span of open water
• Larger the fetch the bigger the wave
3.3 WAVES AND TIDESWaves
3.3 WAVES AND TIDESWaves
Seas
• Sharp peaks stretch over trough Move away get faster than speed of wind
3.3 WAVES AND TIDESWaves
Swells Waves settle
3.3 WAVES AND TIDESWaves
Surf Bottom forces water to move elongated ellipses Wavelength gets shorter Waves “pile up” becoming higher & steeper until
they fall forward
3.3 WAVES AND TIDESWaves
Water affected by mixture of waves Two crest adding to make a higher wave (wave
reinforcement) As high as ten stories
Trough & crest combine & cancel out the wave (wave extinction)
3.3 WAVES AND TIDESTides
Influence marine organisms Organisms are exposed & submerged on shore Drive circulation of bays and estuaries, trigger
spawning
3.3 WAVES AND TIDESTides
Why Are There Tides? Gravitational pull of sun & moon & rotation of
Earth, moon, & sun Moon’s influence
Gravity strongest on side of earth closest - pulls water in ocean toward it
Opposite side furthest from moon - pull is weakest
Earth’s rotation is like unbalanced tire (wooble) creates a centrifugal force - makes the
oceans bulge out toward the moon & away from moon
3.3 WAVES AND TIDESTides
Why Are There Tides? Sun ½ as strong as moon because so far
away Full & new moon (sun moon in line)
Tidal range (difference between high and low tide) is large
Spring tides First and third quarter
Sun & moon at right angles partially cancel each other out – tidal range small
Neap tides
3.3 WAVES AND TIDESTides
Why Are There Tides?
3.3 WAVES AND TIDESTides
Tides in the Real World Tides vary depending on location and the shape
and depth of the basin
3.3 WAVES AND TIDESTides
Tides in the Real World
• Diurnal tides
1 high, 1 low
• Semidiurnal tides
2 highs, 2 lows
• Mixed semidiurnal tides
2 highs, 2 lows of different heights.
3.3 WAVES AND TIDESTides
Tides in the Real World East coast of N. America & most of Europe &
Africa have semidiurnal tides (2 highs and 2 lows)
West coast of USA & Canada mixed semidiurnal tide- successive tides of different height
Diurnal ( 1 high and 1 low) rare on Antarctica and parts of Gulf of Mexico, Caribbean, & Pacific
3.3 WAVES AND TIDESTides
Tides in the Real World Tide tables give predicted time and height of
high and low tides Determined by local geology
Weather like strong winds can cause water to pile on the shore creating higher tide than predicted