Ch. 6
WATER AND OCEAN
STRUCTURE
The Water Molecule
Water is a molecule formed by the
chemical bonds between two hydrogen
atoms and one oxygen atom.
 The covalent bond between the atoms
forms a polar molecule that is slightly
charged at each end.

1,2
The Water Molecule
The polar nature of the water molecule
allows for each end to attract other
water molecules.
 When one hydrogen ends attracts the
oxygen end of another molecule it is
called a hydrogen bond.
 This attraction leads to cohesion.

3,4
The Water Molecule
The Water Molecule
Cohesion gives water an unusually high
surface tension, which results in a
surface “skin”.
 The tendency for water to stick to other
materials is adhesion.
 Cohesion and adhesion are the
properties that allow water to soak
through fabrics.

6
The Water Molecule
Surface tension is the measure of how
difficult it is to stretch or break the surface
of a liquid
Water has the highest
surface tension of all
common liquids
7,8
The Water Molecule
When water molecules vibrate, more
red light is absorbed, leaving more
space for blue light to be reflected.
 This gives water its blue color.

7
Water and Heat
Temperature vs. Heat
 Temperature is a measure of how fast
the molecules in a substance are
moving
 Heat is a measure of how much energy
has to be put into (or gotten out of) a
substance to change its temperature, or
“state” (solid, liquid, gas)
10,11
Water and Heat
Different substances have different heat
capacities.
 Heat capacity is a measure of the heat
required to raise the temperature of 1
gram 1°C and is measured in calories.

12
Water and Heat
Because of the hydrogen bonds in
water, it has the ability to
absorb/release large amounts of heat
while changing relatively little in
temperature.
 Water’s heat capacity is among the
highest of known substances.

13,14
Water and Heat
Most substances become more dense
as they get colder.
 Water though does not behave as other
liquids.
 It does become more dense as it cools
but becomes less dense as it
approaches freezing.

15
Water and Heat
The density curve shows that as water
losses heat, its density increases.
 As it nears freezing though, the
hydrogen bonds become rigid and
expand, thus decreasing its density.
 This explains why ice floats even
though it is in a solid state.

16
Density of Pure Water
Water and Heat
As liquid
absorbs/releases
heat energy, its
phase will change.
 Both the solid and
gas phases are less
dense than the liquid
phase.

water vapor
ice
liquid water
Water and Heat



Sensible heat is what we sense from different
temperatures.
As a sample of water losses heat, its
temperature does not change until the entire
amount has lost 80 calories of heat energy.
The energy needed to change state (ice to
water, water to vapor) is referred to as latent
heat.
17,18
Water and Heat
Water and Heat

There are two types of latent heat
– Latent heat of fusion – some of the
hydrogen bonds break when freezing
occurs
– Latent heat of vaporization – all of the
hydrogen bonds break during vaporization
which requires more heat
19
Evaporation (surface vaporization) from
lakes, oceans, rivers, etc. occurs for
temperatures lower than 100 oC.
But it
requires
more energy
to do so
Water and Heat
Seawater is about 96.5% pure.
 The added dissolved particles and
gasses change the properties.

– Less calories are needed to raise
temperature,
– lower freezing point (-1.91°C),
– evaporation is slowed by the salt,
– more dense than pure water
20,21
Global Thermostatic Effects



Thermostatic properties are those that act to
moderate changes in temperature.
Since water has a very high heat capacity, it
is affected little by increases in heat energy.
Thermal inertia is the tendency to resist a
change in temperature with the gain/loss of
heat energy.
22
Global Thermostatic Effects
Temperature on land can vary as much
as 140°C between the hottest and
coolest places on Earth.
 The water in the ocean only varies
34°C.

Global Thermostatic Effects



Currents, in the ocean and atmosphere,
between the poles and the equator equalize
the heat imbalance.
It is the transfer of heat from location to
location that generates the ocean currents
and influences weather patterns.
Masses of moving air accounts for 2/3 of
poleward heat transfer with ocean currents
moving the other 1/3.
23,24
Density of the Ocean
Salt water density is about 1.025 g/mL
compared to pure water at 1.00 g/mL.
 Cold, salty water is more dense than
warm, less salty water.
 It’s density increases with salinity and
pressure and decreases with
temperature.

25,26
Density of the Ocean

The ocean can be divided into three
zones:
– Surface zone (mixed layer)
– Pycnocline
– Deep-ocean
27
Density of the Ocean
Surface zone (mixing layer):
 Temperature and salinity are relatively
constant in the surface zone due to waves
and currents keeping it well mixed.
 It contains the least dense water and only
accounts for about 2% of all ocean water.
 Extends to a depth of 150 m but can range
from 0 m to 1,000 m in some areas.
28
Density of the Ocean
Pycnocline:
 In the pycnocline zone, density
increases as depth increases.
 This zone keeps the surface layer and
the deep ocean layer from mixing.
 It accounts for 18% of the ocean’s
volume of water.
29
Density of the Ocean
Deep-ocean:
 The deep ocean zone occurs in the midlatitudes below 1,000 m with little
change in density throughout the zone.
 Accounts for 80% of all ocean water.
30
Density of the Ocean


The layers of the ocean are distinct water
masses- a body of water with characteristic
temp., salinity, and density.
This layering traps about 80% of dense water
at great depths below the pycnocline, only
allowing the other 20% to actively circulate
and interact with its surroundings.
30
Temperature of the Ocean
As the temperature of water decreases.
Its density increases.
 There are three layers based on
temperature differences

– Surface
– Thermocline
– deep
31
Temperature of the Ocean
Not all zones are the same due to
exposure to the sun.
 The surface layer is thicker in the
tropics.
 In the polar areas, there is a general
lack of a thermo cline since the surface
temperature is not that much greater
than the deep water.

32
Identify these layers of the ocean according to
temperature.
Salinity of the Ocean

The ocean can be layered based on
salinity as well with the three layers as
– Surface
– Halocline
– Deep

The halocline and the thermocline often
coincide creating a more pronounced
pycnocline.
33,34
Ocean Surface salinities
Refraction, Light, & Sound
Refraction of light and/or sound occurs
when the wave enters a medium of
different density.
 When light enters the water, it bends at
an angle because the wave travel at
different speeds in different mediums.
 The bend of the angle must always be
other than 90° to refract.

35,36
Refraction, Light, & Sound
The speed of light is about ¾ slower in
water than in air.
 Because of this, water effectively
refracts light.
 The refractive index is a ratio
representing the degree to which light is
refracted.

37
Refraction, Light, & Sound
The higher the refractive index, the
greater the bending of waves between
media.
 Water’s refractive index increases with
salinity.
 This refraction can be seen when
looking at a pencil in water or trying to
find a coin at the bottom of a pool.

38
Refraction, Light, & Sound
Light in the Ocean
Light is radiant energy (or electromagnetic
radiation) that travels as waves through
space, air, and water.
 The wavelengths of the visible spectrum
determine the color that is seen.
 Shorter wavelengths are bluer while
longer wavelengths are redder.

39
Light in the Ocean
Water absorbs nearly all
electromagnetic radiation, with only blue
and green passing through water at any
great distance.
 When sunlight does reach the water, it
is scattered and absorbed.
 The greater the density of the water, the
greater the affect.

40,41,42
Light of the Ocean
Absorption of light is determined by the
structure of the water molecule.
 As light travels through the water
column, the molecules begin to vibrate,
turning the light into heat energy.
 This is why the depths of the ocean are
dark.

42,43
Light in the Ocean
The thin area of lighted water in the
surface zone is called the photic zone.
 In the very clearest waters, this zone
extend 600m deep but a typical depth is
around 100m.
 Along the coast the depth is only about
40 m.

44
Light in the Ocean
All of the production of food occurs in
the photic zone, this heated by the sun.
 It is therefore very important to the
balance of life in the ocean.
 The area below this is called the aphotic
zone, without light, due to its darkness.

45
Light in the Ocean
Different depths of the ocean absorb
different electromagnetic wavelengths.
 The very surface absorbs infrared
radiation which in turn heats the water.
 The first meter of depth absorbs 71% of
the red light.
 With depth, eventually the yellow and
orange are absorbed.

47
Light in the Ocean
By 300m even blue is absorbed and
converted into heat.
 It is because of the absorption of certain
colors and the reflection of the blue that
gives the ocean it’s color.

48
Light in the Ocean

Waters with others color, the Red Sea,
appear to have shades of color other
than blue due to dissolved particles
within the water molecule.
Sound in the Ocean
Sound waves are created from changes
in pressure.
 The intensity of sound waves decreases
in water due to scattering, spreading,
and absorption.
 Ever tried talking under water?
 Eventually, the sound energy is
49
converted into heat.

Sound in the Ocean
Sound waves travel much farther in the
ocean than light which is why many
marine animals use sounds to guide
them instead of light.
 The speed of sound in the surface layer
of seawater is 5 times greater than that
of light.

50
Sound in the Ocean
The speed of sound is dependent on
temperature and pressure.
 As they increase, so does the speed of
sound.
 Sound travels faster in warm water
since it has more vibrating molecules
than in cooler water.

51,52
Sound in the Ocean
The speed of sound decreases as the
depth nears 1000m due to the lower
temperatures but it begins to increase
after this depth.
 It increases because the increasing
pressure compensates for the lacking
temperature.

53
Sound in the Ocean

It is thought that the speed of sound
may be greater at the deep ocean basin
than it is in the surface zone due to the
great pressures of that depth.
Sound in the Ocean
Sound in the Atlantic reaches a
minimum at about 1200m and 600m in
the Pacific.
 Sound at these depths is efficient
enough that a depth charge detonated
in the Indian Ocean was heard along
the Oregon coast.

Sound in the Ocean
At times this minimum depth was used
to save lives.
 Those stranded at sea would drop
explosives, detonating at the minimum
depth so that stations on land would
receive the signal.
 This depth is now called the sofar layer,
for sound fixing and ranging.

Sound in the Ocean
As sound waves travel in the ocean,
they can split and bend outward and
away from each other.
 The area between the sound waves is
called the shadow zone.
 In this zone, the sound waves cannot
bounce back to alert of a submarine
being there, etc. , since they do not
54,55
reach this area.

Sound in
the Ocean