Transcript OCEANOGRAPHY

OCEANOGRAPHY
Physical and Chemical
Properties
Outline
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1. Chemical Make-Up of Water
2. Heat Capacity of Water
3. Salinity of Water
4. Density of Water
5. Viscosity
6. Surface Tension
7. Pressure
8. Transmission of Light in Water
9. Transmission of Sound in Water
10. Thermal Layers in Water
11. Dissolved gases
World Oceans
•
Long Island
•
Water Cycle
•
• Hi, I’m Special. Do You Know Why?
1. Chemical Make-Up of Water
• H2O – 2 hydrogen joined together with
1 oxygen
1. Chemical Make-Up of Water
• Water molecules are dipolar with a + charge on
the hydrogen side and a – charge on the
oxygen side.
Chemical Make-Up continued
• Hydrogen and Oxygen share electrons
forming a strong covalent bond. It is
hard to break the hydrogen and oxygen
molecules apart.
• There are also weak hydrogen bonds
between one water molecule and another.
These bonds are more easily broken.
Properties of Water
Video
Special Properties of water
What is so special about water?
What do we use the oceans for?
Dangers of oceans.
Heat Capacity
• Water has the ability to absorb or give off
heat without experiencing a large
temperature change.
• Water changes temperature at 10C
degree per gram per calorie in the liquid
state.
Heat Capacity
• Note: Organisms living in sea water
experience less seasonal temperature
fluctuation than those living in air, sand, or
wood. At 1,000 m the ocean is the most
thermally stable environment on earth with
an average temperature of 3.5 degrees
Celsius.
SALINITY
• Salinity – is the total amount of dissolved
ions in water.
• It is measured in parts per thousand (ppt)
0/00.
• Salts such as NaCl (sodium Chloride) split
apart and are attracted to the charged
poles of the water molecule.
• Na(+) is attracted to oxygen side(-),
• Cl(-) is attracted to hydrogen side(+)
SALINITY
• Seawater is:
– 96.5% or 965 ppt pure water
– 3.5% or 35 ppt dissolved ions
– Many of these dissolved ions are inorganic
salts from weathered rocks.
SALINITY
Salinity is altered by processes that add or
remove salts from the sea.
1. Evaporation – salinity increases
2. Precipitation – salinity decreases
3. River runoff – salinity decreases
4. Freezing of sea ice – increases the
salinity of surrounding water
5. Thawing of sea ice – decreases the salinity
of surrounding seawater
SALINITY
• Salinity and the Water Environment
– Freshwater - 0 – 6 ppt
– Brackish - 7 – 22 ppt
– Seawater - 23 – 40 ppt
OTHER SUBSTANCES
DISSOLVED IN WATER
• 1. Dissolved gases – O2, CO2
• 2. Organic compounds from living
organisms
– Wastes products, fats, oils, amino acids
3. Pollutants
DENSITY
• Density=mass/volume
• Temperature and Density
• Water above 40C decreases in density as
temperature increases
• Water increases in density as it’s temperature
decreases until it reaches 40C
• Water is most dense at 40C, then decreases in
density until it freezes
DENSITY
• Water Density and Salinity
• Water density is affected by the salts
dissolved in it. The more salt it contains,
the denser it becomes.
• The density of fresh water at 40C is
1.000g/ml
• The density of seawater at 40C is
1.028g/ml
DENSITY
• Water of low density floats
• Water of high density sinks
• Cooler water with high salinity is more
dense and will therefore cause surface
water to sink
Density Layers in Water
SALINITY, DENSITY,
TEMPERATURE GRAPH
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VISCOSITY
• Viscosity is the tendency of water to resist
external forces that would separate its
molecules (cohesion)
• Viscosity reduces the sinking tendency of
some objects and organisms which could
allow them to sink or float slowly.
• Viscosity slows down swimming due to
frictional drag.
VISCOSITY
• COLD water has a greater viscosity than
Hot water.
• Greater salinity results in greater viscosity.
SURFACE TENSION
• The mutual attraction of water molecules
creates a flexible molecular skin over the
water surface.
• Note: Both viscosity and surface tension
are temperature –dependent increasing
with decreasing temperature.
– Seawater at 00C is 25%more viscous than
seawater at 200C
Water Strider
PRESSURE
• Hydrostatic Pressure - is due to the weight
water pressing on submerged objects.
• Pressure = force/surface area
• 1atm = 14.7 pounds per square inch
• As an object descends to a greater depth the
pressure from the atmosphere and the water
pushes on it.
• Every 10 meters of depth exerts an additional
1 atmosphere of pressure on an object.
PRESSURE
• 1 atm (atmosphere) of
pressure from the air
surrounding the earth
is pushing on the
oceans, lakes, rivers
and ponds.
• For each additional
10 meters of depth
there is 1 more
atmosphere of
pressure.
PRESSURE
• 1 atm (atmosphere) of
pressure from the air
surrounding the earth Depth (m) Pressure
is pushing on the
(atm)
oceans, lakes, rivers
0
(surface)
1
and ponds.
10
2
• For each additional
10 meters of depth
20
3
there is 1 more
60
7
atmosphere of
pressure.
PRESSURE
• Marine and freshwater organisms bodies
change to equal the pressure of the water
as they swim to different depths.
• Some BENTHIC ORGANISMS are
subjected to a pressure of 340 atm.
• SPERM WHALES – dive from the surface
to a depth of 2,250 m and return in 1 hour.
PRESSURE
• Affects of Hydrostatic Pressure on Life
Functions
• Gases become more soluble at high
pressures.
• Gas filled spaces in an organism may
expand or contract with changes in depth.
• Some enzymes are inactivated.
• Metabolic Rates for a given temperature
tend to be slightly higher.
Pressure on diver
• Pressure on diver +1,248 psi
PRESSURE
Depth
(m)
Water
Volume
Pressure of air in
(atm)
lungs
(atm)
0
1
10
40
5.0
Light in Water
• Transparency – seawater is relatively
transparent allowing photosynthesis to
proceed at some distance below the
surface.
• Water is more transparent to some colors
than others. In clear water, blue light
penetrates deepest making deep clear
ocean water appear blue. Red is absorbed
at the surface.
Light in Water
• 70% of the photosynthesis in the world takes
place in the uppermost layer of the ocean.
• Some light is reflected off the surface.
• Light penetrating the surface is refracted
(bends) because light travels faster in air
than in water. The speed of light in water is
3/4 of its speed in air. Refraction increases
with greater salinity.
• Greater abundances of solids (dust, salts, bits of
body tissue) in the water decrease the depth of
light penetration.
Transmission of Light
Transmission of Light in Water
Refraction
SOUND IN THE SEA
• Sound can travel much greater distances
through water than light before being
absorbed.
• Because sound travels so efficiently
through water, many animals use sound
rather than light to see. (ex. Sperm Whale)
• The speed of sound in water is about
3,345 miles per hour but fluctuates with
depth.
SOUND IN WATER
• Sound waves refract (bend) toward layers
of lower sound velocity.
• Sound waves made in the minimum
velocity layer (SOFAR – SOund Fixing
And Ranging layer)
• Sound in the SOFAR layer can travel for
thousands of kilometers.
THERMAL LAYERS
• Water is warmer near the surface.
• Then as one descends the temperature of
the water gets cooler
• There is a layer of rapid temperature just
below the photic zone. This area is called
the themocline.
• In the deepest water even at the equator,
the water temperature is around 40C.
GASES IN WATER
• Water contains dissolved nitrogen,
oxygen, carbon dioxide, and other gases.
• Cold water can hold more dissolved gas,
(ex. oxygen) than warm water.
• Fresh water can hold more dissolved
gas than seawater.
GASES IN WATER
• Which body of water holds the most
dissolved oxygen?
• 410F freshwater
• 410F seawater
• 740F freshwater
• 740F seawater