SEA WATER
ENVIRONMENT
OCEANS
The earth’s oceans make up
more than 70% of its total
surface area.
OCEANS
Global oceans participate in the global
energy balance ...
by transporting heat energy, which is
preferentially received in the tropics by solar
radiation, toward the polar regions. Over
half of the solar energy reaching the earth is
first absorbed by oceans and then
transmitted to other regions.
OCEANS
Global oceans take excess CO2 from
the atmosphere ...
at a rate that depends on ocean
temperature.
The partial pressure of CO2 in cold water is
depressed by enhanced solubility and (in the
spring bloom) phytoplankton growth making
cold water a sink for atmospheric CO2 .
OCEANS
Global oceans play a significant role in
determining where and how much
water vapor enters the atmosphere
which in turn influences the global energy
balance. Ocean processes are slow in
comparison to atmospheric processes, so
changes in ocean structure can introduce slow
changes of climate.
OCEANS
There are actually just three distinctly separate oceans
in the world today: the World Ocean, the Black Ocean
and the Caspian Sea.
The largest ocean on earth is the World Ocean, which is
continentally divided into five smaller parts, which
include the Atlantic Ocean, the Pacific Ocean, the Indian
Ocean, the Arctic Ocean and the Antarctic Ocean.
Smaller portions of these oceans are typically classified
as either seas, gulfs or straits.
The Mediterranean Sea unofficially became the world’s
fourth ocean.
OCEANS
Pacific Ocean
the largest ocean; covers 35% of the earth; is almost
half of all the oceans, as big as the other four oceans
combined. As the earth spins around, there is a
viewpoint from outer space where all you can see is the
Pacific Ocean.
Atlantic Ocean
is the second largest ocean; covers 21% of the earth; is
a little bigger than half as big as the Pacific Ocean.
PACIFIC YESTERDAY
OCEANS
Indian Ocean
is the third largest ocean; covers 15% of the earth.
Antarctic Ocean
also called the Southern Ocean; circles the globe and
surrounds the southern continent of Antarctica.
Arctic Ocean
covers the earth's north pole; is so cold that its surface
is often frozen during the winter.
SEA WATER
Properties
- physical
- chemical
- biological
Temperature
Tropical ocean water is warm, provides a stable
environment for solidified calcium carbonate.
Corals, clams and other sea creatures make
hard body parts from calcium carbonate salts
dissolved in the water. Solidified calcium
carbonate tends to dissolve faster in cold water.
VERTICAL MIXING
Equatorial surface currents collect heat, which is ultimately shed to the
atmosphere by the time the surface currents reach the North Atlantic. Once
cooled, the water sinks to the ocean bottom, reemerging ahundred or more years
later in the Indian or Pacific Oceans.
RESIDENCE TIMES OF WATER
Reservoir
Glaciers
Seasonal Snow Cover
Soil Moisture
Groundwater: Shallow
Groundwater: Deep
Lakes
Rivers
Typical residence times
20 to 100 years
2 to 6 months
1 to 2 months
100 to 200 years
10,000 years
50 to 100 years
2 to 6 months
SEA WATER
SEA WATER
Sea water has been
defined as a weak
solution of almost
everything !
COMPOSITION
Water in oceans and
seas is salty !
Salt builds up in the ocean because the
only way water can leave the ocean is
through evaporation. And when the water
evaporates it doesn't take the salt with it.
Salts dissolved in sea water
3,7% Mg
Ca K Minor salts
7,7% SO4
30,6% Na
55% Cl
Six major ions make up >99% of the total
dissolved in seawater.
They are sodium ion (Na+), chloride (Cl-), sulfate
(SO42-), magnesium ion (Mg2+), calcium ion (Ca2+),
and potassium ion (K+).
SALINITY
Salinity is related to the concentration
of dissolved salts in seawater.
Salinity has no units. The PSU or "practical salinity
unit" is incorrect, although frequently used. Salinity
is approximately equal to the weight, in grams, of
salt dissolved in 1000 g of seawater. This would be
the salt concentration in parts per thousand (o/oo).
COMPOSITION
One of the most baffling questions
in modern science is why
the oceans maintain an almost
constant composition
including every element known to
man. And these proportions never
seem to change.
COMPOSITION IS
CONSTANT
CONCENTRATION
IS DIFFERENT
SALINITY
Average salinity of the oceans is 35 o/oo.
The saltiest water (40 o/oo) occurs in the Red Sea and
the Persian Gulf, where rates of evaporation are very
high. Of the major oceans, the North Atlantic is the
saltiest; its salinity averages about 37.9 o/oo.
Low salinities occur in polar seas where the salt water
is diluted by melting ice and continued precipitation.
The Baltic Sea ranges in salinity from about 5 to 15
o
/oo. The salinity of the Black Sea is less than 20 o/oo.
SALINITY CHANGES
CONSEQUENCES OF
CONSTANT COMPOSITION
Measure Clconcentration and ... calculate salinity
because of seawater's constancy of chemical composition, the total
salinity can be determined from the concentration of the chloride
ion since the ratios of sodium to chloride to magnesium to calcium
and to any other major constituent remain constant
SEA WATER AND RIVER WATER
obviously are very different from
each other
(1) Sodium and chloride (the components of
common table salt) constitute a little more
than 85 % of the dissolved solids in ocean
water and give to the water its characteristic
salty taste, but they represent less than 16 %
of the salt content of river water.
SEA WATER AND RIVER WATER
obviously are very different from
each other
(2) Rivers carry to the sea more calcium than
chloride, but the oceans nevertheless contain
about 46 times more chloride than calcium.
SEA WATER AND RIVER WATER
obviously are very different from
each other
(3) Silica is a significant constituent of river
water but not of sea water.
SEA WATER AND RIVER WATER
obviously are very different from
each other
(4) Calcium and bicarbonate account for nearly
50 % of the dissolved solids in river water yet
constitute less than 2 % of the dissolved solids
in ocean water.
GASES
IN THE OCEANS
CO2
Carbon dioxide is considered a trace
gas in the atmosphere because it is
much less abundant than oxygen or
nitrogen. However, this trace gas plays
a vital role in sustaining life on Earth
and in controlling the Earth's climate
by trapping heat in the atmosphere.
OCEAN IS A SINK FOR CO2
The oceans play an important role in regulating the
amount of CO2in the atmosphere because CO2 can
move quickly into and out of the oceans. Once in the
oceans, the CO2 no longer traps heat. CO2 also
moves quickly between the atmosphere and the
land biosphere (material that is or was living on
land).
Of the three places where carbon is stored —
atmosphere, oceans, and land biosphere —
approximately 93 % of the CO2 is found in the
oceans.
Oxygen dissolves in ocean surface water from the
atmosphere. Photosynthesis is also a source of
oxygen to ocean surface waters. Oxygen is
consumed by respiration. Rarely, animals and
bacteria use all of the oxygen in sub-surface waters,
which become anoxic. This can only happen if the
waters are isolated from the atmosphere in some
way.
Carbon dioxide is consumed during photosynthesis
and released during respiration. It can also be
exchanged with (dissolved from and released to) the
atmosphere. Carbon dioxide can react with water to
form bicarbonate and carbonate ions.
CO2 + H2O  HCO3- + H+  CO32- + 2H+
These reactions control the acidity (pH) of seawater.
pH of sea water
pH of sea water
CO2 + H2O
 HCO3- + H+
 CO32- + 2H+
these reactions control the
acidity (pH) of water
pH of sea water
normal pH values in seawater are about
8.2 at the surface and decrease to about
7.7 in deep water
the different salts in sea water tend to
buffer the water
HYDROLOGIC OPTICS
Hydrologic optical principles
determines the penetration of
biologically damaging ultraviolet
light underwater.
HYDROLOGIC OPTICS
The depth to which sunlight penetrates into the
water determines the transparency of a water
body. Light penetration is dictated by the
composition of the water. Water itself strongly
absorbs light in the red region of the light
spectrum, which is why clean, clear waters are
blue. Other components in the water that impact
its optical properties, include colored dissolved
organic matter (CDOM), decaying organic matter,
inorganic particulate matter, such as silt and clay,
and phytoplankton.
At about 20 feet deep, this diver's red weight belt is
nearly colorless, while the color in his blue flotation
vest is solid and true.
LIGHT PENETRATION
Light from the sun
A b s o r b e d
l i g h t
Scattered
light
PHYTOPLANKTON
DISSOLVED
ORGANICS
TOTAL SUSPENDED
SOLIDS (PARTUCULATES)
The intensity of this light decreases rapidly
with water depth, for example:
*
*
*
*
*
only 73% of the surface light reaches a depth of
1 centimeter
only 44.5% of the surface light reaches a depth
of 1 meter
22.2% of the surface light reaches a depth of 10
meters
0.53% of the surface light reaches a depth of
100 meters
0.0062% of the surface light reaches a depth of
200 meters