chapter 3 chemical and physical features of seawater and world oceans

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


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


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


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.


The Three States of Water Hydrogen Bonds

Associated with Basilisk Lizard (Jesus Lizard) http://www.youtube.com/watch?v=45yabrnryXk&edufilter=DQBPVNZ5nlfNZmzO0OgIrQ

http://www.youtube.com/watch?v=45yabrnryXk&edufilter=DQBPVNZ5nlfNZmzO0OgIrQ


The Three States of Water Weak hydrogen bonds form between to the

positive end and the negative end of different water molecules Liquid

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Solid http://www.visionlearning.com/library/flash_viewer.php?oi

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The Three States of Water

Solid

Gas Liquid


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


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


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


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)


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


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)


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


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

http://www.youtube.com/watch?v=tzBJy6BXf5Y&edufilter=DQBPVNZ5nlfNZmzO0OgIrQ


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?


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.


Salinity, Temperature, and Density Density controlled more by temperature than

salinity There are exceptions therefore salinity &

temp need to be measured to determine density


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


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


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


Pressure 压力

• On land, organisms are under 1 atm at sea level

Marine organism have the pressure of the atmosphere & water


Pressure With every 10m increase depth another atm is

added


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

http://www.youtube.com/watch?v=CCmTY0PKGDs&edufilter=DQBPVNZ5nlfNZmzO0OgIrQ

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.


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.


Wind Patterns•Winds driven by heat energy from sun


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


Wind Patterns•Westerlies at middle latitudes move in opposite direction

•Polar easterliesat high latitudesmost variablewinds


Surface Currents

Direction of wind currents


Surface Currents

Produce Ekman transport upper part of water column moves

perpendicular (90o) to wind direction to right N. Hemisphere & left in S. Hemisphere


Surface Currents•Global wind patterns and the Coriolis effect produce gyres (+sun’s heat & gravity)

•Gyres large circular systems of ocean currents


Surface Currents•West side of gyres carry warm water to higher latitudes while cold current flow on eastern sides


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


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



•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.



•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


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



The Three-layered Ocean•Intermediate layer/ 中间层 depth of 1000 to 1500m

• Main thermocline rarely breaks down & in open ocean



The Three-layered Ocean•Deep or bottom layers/ 深或底层

• Below 1500 m• typically less than 4°C



•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 .



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


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.


Waves Fetch -span of open water

• Larger the fetch the bigger the wave


Seas

• Sharp peaks stretch over trough Move away get faster than speed of wind


Swells Waves settle


Surf Bottom forces water to move elongated ellipses Wavelength gets shorter Waves “pile up” becoming higher & steeper until

they fall forward


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


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


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

http://en.wikipedia.org/wiki/File:Tidal_Range.jpg


Why Are There Tides?


Tides in the Real World Tides vary depending on location and the shape

and depth of the basin


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.


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


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

chapter 3 chemical and physical features of seawater and world oceans

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