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seasonal changes
sea level may change because of thermal expansion or contraction of the
water, and also by: (a) melting of glaciers. During a glacial epoch a large quantity of water is stored in glaciers and the sea level is low; during a period of
maximal glaciation the sea level is probably about 130 m lower than at present. If the climate warms, glacial melting increases and the sea level will rise;
if all the present-day glaciers melted, a sea-level rise of about 65 m would
occur; and by: (b) changes in the mean depth of the ocean floor. Young
ocean floor is relatively warm (~plate tectonics); cooling and shrinking with
increasing age causes the ocean floor to deepen. Consequently, if the global
mean age of the ocean floor is low, the mean depth of the oceans is low and
the sea level is high; vice versa: if the mean ocean floor is old the sea level is
low. On a regional scale, sea-level changes may also originate from isostatic
movements of land masses. ~climatic variation.
seals ~mammals, marine.
sea mile ~nautical mile.
seamount an isolated, steep-sloped submarine mountain, roughly circular or
elliptical in plan and rising more than 900 m above the ocean floor. Most are
extinct volcanoes. ~volcanism and ~tablemount.
sea salt production of salt by evaporation of seawater (crystallization) has been
practiced for thousands of years and was described already by the ancient
Egyptians, Greeks, and Romans. The early Scandinavians produced brine by
removing ice from freezing seawater. Crude salt was obtained by means of
continuous seawater flow through shallow artificial ponds where evaporation by sun and wind followed. Almost dry, this product has a very bitter
taste caused by high content of magnesium salts; it contains only about
65 % sodium chloride. The first precipitate in brine concentration is gypsum
which can be removed before the crystallization of sodium chloride begins.
Later on it was noticed that a much purer product could be obtained by
draining a small amount of residual brine from the crude salt. Solar salt
production still contributes over 40 % of the total world sodium chloride
production.
sea snakes ~Reptilia, marine.
seasonal changes at increasing distance from the equator, the amount of radiation
of sunlight on the earth's surface follows at an increasing degree an annual
cycle, leading to darker and colder, versus lighter and warmer parts of the
year with in between the transition periods (the seasons). In the sea these
fluctuations are dampened considerable, due to the large heat capacity of the
enormous waterbody, and due to convection: transportation of warmth by
seasonal changes
sea level may change because of thermal expansion or contraction of the
water, and also by: (a) melting of glaciers. During a glacial epoch a large quantity of water is stored in glaciers and the sea level is low; during a period of
maximal glaciation the sea level is probably about 130 m lower than at present. If the climate warms, glacial melting increases and the sea level will rise;
if all the present-day glaciers melted, a sea-level rise of about 65 m would
occur; and by: (b) changes in the mean depth of the ocean floor. Young
ocean floor is relatively warm (~plate tectonics); cooling and shrinking with
increasing age causes the ocean floor to deepen. Consequently, if the global
mean age of the ocean floor is low, the mean depth of the oceans is low and
the sea level is high; vice versa: if the mean ocean floor is old the sea level is
low. On a regional scale, sea-level changes may also originate from isostatic
movements of land masses. ~climatic variation.
seals ~mammals, marine.
sea mile ~nautical mile.
seamount an isolated, steep-sloped submarine mountain, roughly circular or
elliptical in plan and rising more than 900 m above the ocean floor. Most are
extinct volcanoes. ~volcanism and ~tablemount.
sea salt production of salt by evaporation of seawater (crystallization) has been
practiced for thousands of years and was described already by the ancient
Egyptians, Greeks, and Romans. The early Scandinavians produced brine by
removing ice from freezing seawater. Crude salt was obtained by means of
continuous seawater flow through shallow artificial ponds where evaporation by sun and wind followed. Almost dry, this product has a very bitter
taste caused by high content of magnesium salts; it contains only about
65 % sodium chloride. The first precipitate in brine concentration is gypsum
which can be removed before the crystallization of sodium chloride begins.
Later on it was noticed that a much purer product could be obtained by
draining a small amount of residual brine from the crude salt. Solar salt
production still contributes over 40 % of the total world sodium chloride
production.
sea snakes ~Reptilia, marine.
seasonal changes at increasing distance from the equator, the amount of radiation
of sunlight on the earth's surface follows at an increasing degree an annual
cycle, leading to darker and colder, versus lighter and warmer parts of the
year with in between the transition periods (the seasons). In the sea these
fluctuations are dampened considerable, due to the large heat capacity of the
enormous waterbody, and due to convection: transportation of warmth by