Sagitta
276
s
Sagitta arrow worm, ~Chaetognatha.
salinity measure of the concentration of salt in seawater. In order to obtain
accurate comparable figures, an exact definition is necessary. The first definition (1889) was based upon the determination of the mass of all dissolved
salts in one kilogram of seawater by means of evaporation. This approach is
not practical for routine measurements and hence was replaced by a relation
based on the chlorinity titration, which, thanks to the constant composition of
seawater, was sufficiently close to the original definition. A good correlation
exists with chlorinity (the amount of chloride in grams per kg seawater):
S = 1.805 CI+0.03. However, with the possibility of measuring the salt content of seawater as conductivity, as accuracies increased, a new definition
became necessary. In 1978 the "practical salinity" was introduced, based
upon the conductivity of seawater. The (practical) salinity (S) is given by a nondimensional figure, in the ocean within the range S = 30 and S = 40. In older
publications, salinity (related to the older definition) is given in permilles. In
most cases, where the highest accuracy is not required, old and new figures
may be used together indiscriminately.
salinity crisis marine biotic crisis due to excessive salinity. Salinity substantially
greater than that of normal seawater may occur when the exchange of water
with the open ocean is poor, whereas the supply of salts (e.g., by rivers) continues. Moreover, an increase in water temperature or upwelling of
hydrothermal water may lead to the dissolution of preexisting evaporites.
The so-called hypersaline basins are the sites of extensive evaporite formations. The most spectacular development of evaporites in a major ocean
basin occurred in the western Mediterranean at the end of the Miocene
(Messinian), with evaporite thicknesses of up to 2 to 3 km in places. At that
time the Mediterranean is thought to have been completely separated from
the Atlantic, and the event seems to have caused an almost complete absence
of life.
salinometer an instrument which can estimate salinity from a physical property
of seawater. Fundamentally physical properties such as density, refractive
index, sound velocity and electrical conductivity can be used. Since 1960
electrical conductivity has become used widely after the development of an
accurate, fast salinometer by Brown and Hamon. Their inductively coupled
salinometer is electrode-less, has a temperature compensation circuit and
276
s
Sagitta arrow worm, ~Chaetognatha.
salinity measure of the concentration of salt in seawater. In order to obtain
accurate comparable figures, an exact definition is necessary. The first definition (1889) was based upon the determination of the mass of all dissolved
salts in one kilogram of seawater by means of evaporation. This approach is
not practical for routine measurements and hence was replaced by a relation
based on the chlorinity titration, which, thanks to the constant composition of
seawater, was sufficiently close to the original definition. A good correlation
exists with chlorinity (the amount of chloride in grams per kg seawater):
S = 1.805 CI+0.03. However, with the possibility of measuring the salt content of seawater as conductivity, as accuracies increased, a new definition
became necessary. In 1978 the "practical salinity" was introduced, based
upon the conductivity of seawater. The (practical) salinity (S) is given by a nondimensional figure, in the ocean within the range S = 30 and S = 40. In older
publications, salinity (related to the older definition) is given in permilles. In
most cases, where the highest accuracy is not required, old and new figures
may be used together indiscriminately.
salinity crisis marine biotic crisis due to excessive salinity. Salinity substantially
greater than that of normal seawater may occur when the exchange of water
with the open ocean is poor, whereas the supply of salts (e.g., by rivers) continues. Moreover, an increase in water temperature or upwelling of
hydrothermal water may lead to the dissolution of preexisting evaporites.
The so-called hypersaline basins are the sites of extensive evaporite formations. The most spectacular development of evaporites in a major ocean
basin occurred in the western Mediterranean at the end of the Miocene
(Messinian), with evaporite thicknesses of up to 2 to 3 km in places. At that
time the Mediterranean is thought to have been completely separated from
the Atlantic, and the event seems to have caused an almost complete absence
of life.
salinometer an instrument which can estimate salinity from a physical property
of seawater. Fundamentally physical properties such as density, refractive
index, sound velocity and electrical conductivity can be used. Since 1960
electrical conductivity has become used widely after the development of an
accurate, fast salinometer by Brown and Hamon. Their inductively coupled
salinometer is electrode-less, has a temperature compensation circuit and