makes up 97% of the global water inventory, a large portion
of which is constituted as ocean ice. It is important to note
that the sea water which is in the form of ice is completely
unusable for human purposes.
Polar ice-caps are a very significant feature of the present-day
Earth. The outer layer of ice, covered with snow, reflects the
incoming solar radiation more
effectively than land or open water. Thus, a situation is
created where only a small amount of energy is able to penetrate
into the surface water or the underlying land. Once these polar
ice-caps are established, they have the tendency to act in a
The freezing of sea water itself creates a form known as sea-ice.
When sea water freezes, the salts concentrate into small brine
droplets that are trapped within the ice. These brine droplets
become more saline and the freezing point of the droplets becomes
greatly depressed in comparison to that of the ice surrounding
the droplets. Therefore, the brine droplets will remain in the
liquid form at temperatures well below that of the ice formation.
Icebergs make up another major form of ice in the oceans. Icebergs
in the Arctic are carried to sea by valley glaciers from land
masses such as Greenland. These icebergs come in irregular shapes
as they are remnants of thick ice sheets that fringe on the
Arctic Ocean. The icebergs in the Southern Ocean are tabular
icebergs which are formed by the calving of the ice-shelves
found in the Ross and the Wedell Seas.
Sea water itself is very different from freshwater. Two of
the most important properties of sea water are temperature and
salinity, the concentration of dissolved salts. The two properties
work in conjunction to control the density of the water. The
density of water is a major factor which controls the vertical
movement, via condensation, of the ocean waters. The salinity
of sea water is the most important factor in the consideration
of human use. The average salinity of sea water is 35 part per
thousand by weight (3.5 percent by weight). The major ions that
make up 99.9% of sea water are as follows:
Dissolved Constituents Parts
Per Thousand By Weight
dissolved salts of sea water is 300 times that of river water.
The main dissolved constituents in rainwater are sodium and chloride.
The main dissolved constituents of river water are hydrogen carbonate
and calcium. Whereas, the main dissolved constituents of sea water
include sodium and chloride.
|Total Dissolved Salts Milligrams Per
|Note that the TDS of river water is 15 times the TDS of rainwater
while the TDS of sea water is 400 times that of rainwater. This
is the main reason why sea water is not a good source of drinkable
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Water Systems, Division of Clean Water Systems & Stores Inc. All