Salinity of the ocean

Table 10-3 Average temperatures and salinity of the oceans, excluding adjacent seas ...

In this opinion he disagreed with Halley (1715), who suggested that the salinity of the oceans has increased with time, and that the ratio of the total salt content of the oceans to the rate at which rivers deliver salt to the sea could be used to ascertain the age of the Earth. The first really serious attempt to measure geologic time by this method was made by Joly (1899). His calculations were refined by Clarke (1911), who inferred that the age of the ocean, since the Earth assumed its present form, is somewhat less than 100 Ma. He concluded, however, that the problem cannot be regarded as definitely solved until all available methods of estimation shall have converged on one common conclusion. There was little appreciation in his approach for the magnitude of ... 

Classification of the chemical constituents of seawater into conservative, bioactive and adsorbed (Chapter 1) revealed much about the processes that control concentration distributions in seawater of the latter two categories, but little about the conservative elements. Concentrations of the elements that make up most of the salinity of the oceans provide clues to the mechanisms that control their sources and sinks. Thus, the chemical perspective of oceanography revealed by conservative element concentrations is about processes that occur at the ocean boundaries weathering reactions on land, authigenic mineral formation in marine sediments and reactions with the crust at hydrothermal areas. The amount of time some of the dissolved constituents remain in solution before they are removed chemically is very long, suggesting the possibility for chemical equilibrium between seawater and the minerals in the ocean... 

Following the last glaciation, the salinity of the oceans decreased due to melting of the polar ice caps. This decrease in chloride and sodium and other major ions of sea water has led to a lowered concentration in the pore water of the upper seabed. By using the equation for diffusion distance versus time (ca. 10,000 years), calculate how deep this concentration decrease has diffused into the seabed. Diffusion coefficients are given in Chapter... 

The statistical collection and representation of the weather conditions for a specified area during a specified time interval, usually decades, together with a description of the state of the external system or boundary conditions. The properties that characterize the climate are thermal (temperatures of the surface air, water, land, and ice), kinetic (wind and ocean currents, together with associated vertical motions and the motions of air masses, aqueous humidity, cloudiness and cloud water content, groundwater, lake lands, and water content of snow on land and sea ice), nd static (pressure and density of the atmosphere and ocean, composition of the dry ir, salinity of the oceans, and the geometric boundaries and physical constants of the system). These properties are interconnected by the various physical processes such as precipitation, evaporation, infrared radiation, convection, advection, and turbulence, climate change... 

All the chemical elements can be detected in seawater, but obviously with very different concentrations. Among the 90 natural elements, 73 can be detected using the traditional techniques of analytical chemistry the 17 others require finer physical methods and are regarded as trace elements. An important observation, called Murray s law, stipulates that if the salinity of the oceans (the total quantity of salts per kilogram of seawater) varies in space -that is, from one point to another in the world s oceans -and is overall equal to 35 2gl (that is to say, 35%o), then the composition of seawater (as a percentage of the various elements) remains constant whatever the place and the depth. 

Halophiles require salinity to be at least equal to 1.5 M (NaCl) and can survive up until 5 M (NaCl or KCl). At about 35 gl (3.5%), the salinity of the oceans is close to 1.5 M (NaCl) at about 275 gl (27.5%), the salinity of the Dead Sea is close to 4.7 M (NaCl), as well as containing more bromine, potassium, and magnesium and less sulfate than the world s oceans. 

Because temperature (T) and salinity (S) are the main factors controlling density, oceanographers use T-S diagrams to describe the features of the different water masses. The average temperature and salinity of the world ocean and various parts of the ocean are given in Fig. 10-3 and Table 10-3. The North Atlantic contains the warmest and saltiest water of the major oceans. The Southern Ocean (the region around Antarctica) is the coldest and the North Pacific has the lowest average salinity. 

The saltiness of the ocean is defined in terms of salinity. In theory, this term is meant to represent the total number of grams of dissolved inorganic ions present in a kilogram of seawater. In practice, salinity is determined by measuring the conductivity of a sample and by calibration through empirical relationships to the International Association of Physical Sciences of the Ocean (IAPSO) Standard Sea Water. With this approach, salinity can be measured with a precision of at least 0.001 parts per thousand. This is fortunate, considering that 75% of all of the water in the ocean falls neatly between a salinity of 34 and 35. Obviously, these high-precision measurements are required to observe the small salinity variations in the ocean. 

Marcet, A. 1819. On the specific gravity, and temperature, in different parts of the ocean, and in particular seas with some account of their saline contents. Philosphical Transactions Royal Society of London 109 161-208. 

The mathematical models used to infer rates of water motion from the conservative properties and biogeochemical rates from nonconservative ones were flrst developed in the 1960s. Although they require acceptance of several assumptions, these models represent an elegant approach to obtaining rate information from easily measured constituents in seawater, such as salinity and the concentrations of the nonconservative chemical of interest. These models use an Eulerian approach. That is, they look at how a conservative property, such as the concentration of a conservative solute C, varies over time in an infinitesimally small volume of the ocean. Since C is conservative, its concentrations can only be altered by water transport, either via advection and/or turbulent mixing. Both processes can move water through any or all of the three dimensions... 

One point is central life endures. Despite major changes in the composition of the atmosphere of the Earth, repeated ice ages, changes in the salinity of ffie oceans, massive movements of the continents and ffie oceans, and extraterrestrial insults, life endures. Once life had emerged, it proved to be enormously resilient. More man 99% of all the species that ever existed no longer exist, yet we have more species on Farm... 

Besides temperature, a variable isotopic composition of the ocean is another factor responsible for variations in foraminifera. A crucial control is salinity ocean waters with salinities greater than 3.5% have a higher 0 content, because 0 is preferentially depleted in the vapor phase during evaporation, whereas waters with salinities lower than 3.5% have a lower content due to dilution by fresh waters, especially meltwaters. The other factor which causes variations in the isotopic composition of ocean water is the volume of low- 0 ice present on the continents. As water is removed from the ocean during glacial periods, and temporarily stored on the continents as 0-depleted ice, the ratio of the global ocean increases... 

Usually the most publicized and one of the most dramatic examples of ocean water (and adjacent shoreline) pollution involves oil tanker or barge accidents. Most often, the saline waters of the oceans and seas are polluted, although tiiere are instances where such accidents have occurred in fresh and brackish waters. 

Natural processes, operating both at the surface and at great depths, result in most of the ocean being stirred continuously. It is found that the relative proportions of dissolved salts are virtually the same everywhere, although the total salt content (salinity) may show appreciable variations with geography. 

Sea water feed for the stills is pumped from the Halifax River, which at the point of feed intake has a salinity of about 35,000 p.p.m., the same as that of the ocean. Much of the research instrumentation is housed in a centrally located concrete block shelter, which was constructed underground principally to prevent its shading the nearby stills. One of the previously existing buildings on the reservation was renovated to provide an office, a conference room, and equipment storage space. 

Species that live in northern seas may be structurally differentiated by environmental conditions, which vary considerably from the centre to the periphery of the area. Crucial factors are the temperature and salinity of the water and the character of the nutritive base. Populations of cod, herring and flounder exist in two forms, oceanic and coastal (Shatunovsky, 1980). 

Phytoplankton is at one of the initial levels of the trophic hierarchy of the ocean system. As field observations have shown, the World Ocean has a patchy structure formed by a combination of non-uniform spatial distributions of insolation, temperature, salinity, concentration of nutrient elements, hydrodynamic characteristics, etc. The vertical structure of phytoplankton distribution is less diverse and possesses rather universal properties. These properties are manifested by the existence of one to four vertical maxima of phytoplankton biomass. 

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