Opener
CH 3 Features of Seawater
and the World Ocean
Fig. 3.4
Waters of the Ocean
•Earth
•only planet with liquid water on its surface
•80% or more of our bodies
•Water cycle (condensation, precipitation, evaporation)
Properties of Water
•Arrangement of its atoms
•Nature’s solvent
•Covalent and hydrogen bonds
•Polar properties
•Cohesion
•Adhesion
•Heat storage
Water exists naturally on Earth in all
three states
•Hydrogen bonding
•Regulates global temperatures
Density of water
• Density increase as temperature decreases
– 40 C or 390 F
• Below this density decreases as water freezes
• Ice floats on water
Salinity
• Amount of dissolved solids in ocean water
– 35 grams of dissolved solids/kg of ocean water
– Ranges from brackish to hypersaline
• 6 ions
– Chloride, sodium, sulfate, magnesium, calcium,
and potassium
– Constant proportion to each other
Physical Properties of
Pure Water vs Salt Water
• Salt water
•Higher in pH (basic)
•More dense
•Higher boiling point
•Lower freezing point
Seawater
• Dissolved components are added and
removed by variety of processes
o Precipitation
o Runoff
o Melting of icebergs and sea ice
o Evaporation
Fig. 3.6
Salinity, Temperature, and Density
• Salinity of surface water varies considerably
due to surface processes
– Maximum salinity found near tropics
– Minimum found in high – latitude regions
• Halocline
– Layer of rapidly changing salinity
– Deeper waters more constant
• 1000 meters
Fig. 3.7
Seawater Density
• Density increases as temperature decreases
and salinity increases
• Pycnocline
– Rapidly changing density in low – latitude
regions
• Thermocline
– Rapidly changing temperature in high – latitude
regions
Fig. 3.9
Fig. 3.10
Temperature of the ocean; coldest in blue, warmest in red
Dissolved Gases
•Oxygen, Carbon Dioxide, Nitrogen
•Cold water vs warm water
•Oxygen affected by the rate of photosynthesis
•Carbon Dioxide represents 80% of the dissolved
gas in the ocean
Transparency
•Sunlight can penetrate into the ocean
o Photosynthesis
o ROY G BIV
•As depth increases colors are filtered out
•Only blue light remains approx 200ft
•Affected by material suspended and dissolved in
the water
Fig. 3.11
Fig. 3.12
At 30m only blue light remains, (a) natural light (b) flash
Pressure
•Changes with the water depth
•All the weight from above
pushing down
•Pressure increases with depth
o For every 33ft = 1
atmosphere of pressure
o
(1 atm = 14.5 lbs. /sq. ft)
Fig. 3.14
Fig. 3.15
Reverse effect of pressure for deep sea creatures being brought
to the surface.
Critical Thinking
• In unusually cold winters the northern
Black Sea sometimes freezes while the
nearby Adriatic Sea usually doesn’t, even if
it is just as cold. Freshwater runoff gives
the surface of the Black Sea a low salinity
of about 180/00 . What would you guess
about the salinity of the Adriatic?
Ocean Circulation
•Transports;
•heat, nutrients, pollutants, and organisms
•Surface Circulation
•Wind driven is the strongest
•Driven by the sun (thermal)
Fig. 3.16
Earth’s rotation causes an arc in the movement of currents
Coriolis Effect
•Nonlinear movement of
currents
•Right or clockwise in the
Northern Hemisphere
•Left or counterclockwise in
the Southern Hemisphere
Wind Patterns Affect on Currents
•Heat energy
•Equator is warmer than the poles
1.
Air is heated
2.
Less dense and begins to rise
3.
Air gets pulled into pocket
•
curved at an angle due to Coriolis
Effect.
Fig. 3.17
Fig. 3.18
Surface Currents
•Wind push sea surface creating currents
o Surface water moves at an angle from the
wind
o Pushes layer of water below moving it at
an angle
o Continues to move down the water column
resulting in a spiral (Ekman spiral)
Fig. 3.19
Fig. 3.20
Main ocean basin currents combine to form wind – driven gyres.
Global Wind Patterns
•Regulate the earth’s climate
o Transporting heat from tropical to polar
regions
•Affect the distribution of organisms
•Currents shift with the season or weather
Thermohaline Circulation and the
Great Ocean Conveyor
•Ocean is a 3 – dimensional habitat
•Densest water sinks creating layers
(stratified)
•Dense water on bottom and least
dense at the surface
Fig. 3.21
3 – Layered Ocean/Thermocline
•Surface layer – approx. 660ft thick.
o Mixed by wind, waves, and currents.
o Can be heated and warmer than deeper
water
• Intermediate Layer
• Deep or Bottom Layer
Fig. 3.22
Seasonal changes in
surface temperature can
change density of water
causing surface water to
sink, known as
downwelling.
Fig. 3.24
Fig. 3.25
Great Ocean Conveyor as a result of changes in water temperature
and salinity. Critical in regulating earth’s climate.
Just for Fun
• Someone in Beaufort, South Carolina,
throws a message in a bottle into the sea.
Some time later, someone in Perth, on the
west coast of Australia, find the bottle.
Referring to fig. 3.20 and the fold – out map
at the back of your textbook, trace the path
the bottle probably took?