Most all of the sun's energy (solar
radiation) is absorbed at the surface, and has little effect in changing the temperature
of the ocean below a few hundred meters.
Compounding the lack of light penetration into the sea is
the fact that a tremendous amount of heat (energy) is required to alter the temperature of
a large body of water like the ocean, because of the high heat capacity of water, which is
the amount of energy required to raise 1 cm3 of water at atmospheric pressure
Used with Permission of Matthias Tomczak
We can see the variation of ocean temperature with
water depth in the ocean in the graph above. The irregular gray line at the bottom of the
graph is the sea floor and the horizontal line at the top is the sea surface.
Scales for water depth are shown on left, and color codes
for sea water temperature
are listed on right.
Is it now apparent why most of the ocean is cold?