how does salinity in the oceans vary over the globe and what is the likely reasons for this?
828590
The major variable regarding ocean salinity is the 'Water Cycle.' Only pure water evaporates from oceans, lakes and seas. Not salt water. So, any body of water tends to get more salty over time. If all the water evaporates, all that is left is salt. That is why Utah has the great salt flats. The huge lake Bonneville evaporated and left behind miles and miles of salt. \n\nBut in the Water Cycle, the water that evaporates does not just stay up in the air. It forms clouds, rain or snow falls to Earth and flows down rivers back into the oceans, seas and lakes. The water that falls from the sky - not counting any pollution! - is pure water. The rivers and glaciers carry this water - with dissolved minerals and salts - back into the sea. \n\nThe concentration of dissolved minerals and salts of the rivers or glaciers is far less than that in the oceans. So near where fresher water is flowing into the oceans the salinity is lower than that out in the parts of the ocean where there is less rainfall.\n\n;-D There is a lot of water on planet Earth, but not much of it is drinkable! Don't waste water!
90693
At the moment, they are in balance.  The salt in the ocean came from minerals and rocks dissolved over millions of years. To markedly increase salinity in the world's ocean, a substantial quantity of water would have to be lost. In general, our planet biosphere has a set quantity of water. It is either tied up in oceans, living creatures, clouds/vapor, ice or the freshwater sources in wells, rivers, etc. What evaporates from the sea is ultimately returned via rivers, runoff, etc. The melting icecaps is actually a SUBSTANTIAL contributer to the total volume of the seas. However, as sea levels rise, so does rthe capacity to absorb more minerals, so the salinity would fluctuate over a few thousand years and stabilize about where it is now.
552585
Oceanic currents are part of the global system of circulation that distributes the Sun's energy (including warmth) in the planet. Just like the wind currents transport warmer and colder air masses, oceanic currents distribute colder water from the poles to lower latitudes (cold currents are usually deep because cold water sinks under warmer water masses), and warm water from intertropical areas gets transported to higher latitudes (surface currents). \nOceanic currents also differ in their salinity (salt concentration) levels, which is also very important for aquatic organisms as well as for the global circulation, because salinity affects the freezing point of water. Therefore, oceanic currents affect the normal formation of ice, which also affects neighboring land masses and in turn alters the global circulation. \n\nThe influence of oceanic currents is especially important in coastal areas, but the amounts of energy transported by oceanic currents equals the transport by wind currents, and can affect temperature/precipitation balances throughout the world. El Niño (it's complete name is ENSO - El Niño Southern Oscillation) is a good example of the way a change in an oceanic current can alter land climate, e.g. causing droughts.\nAnother example is the Gulf Stream which "warms up" the North Atlantic Ocean and northeaster Europe.\n\nAbout the El Niño-La Niña cycle (ENSO):\nhttp://www.cdc.noaa.gov/ENSO/
977415
Salt water does not have any specific effect on weather formation. But all sources of water whether it is river, lake, pond, sea or ocean; by evaporation affect humidity and therefore the weather conditions.
519909
It's a combination of less sunlight & density currents.\n\nCold salty water is very dense. It sinks. This along w/ surface flow created by winds creates currents in the sea.\n\nCold water ends up on the bottom.\n\nThe amount of geothermal energy located on the ocean floor is negligible here. It only makes a difference on a local scale. The ocean floor is very deep and very large. Too much space for geothermal vents to heat.
112651
The point you are talking about is Cape Agulhas.  I have been there and you can see different colors in the water where the oceans meet.  You do not see a perfect horizontal line dividing the oceans, but you do see bands and pockets of color as opposed to the smooth diffusion you might expect.\n\nThe different colors come from different kinds of plankton living in the water.  While it's true that pure water gets its color from refracting light, the ocean is not at all pure.  Plankton living in the water has a major effect on the color of the ocean. The Indian and Atlantic Oceans have different temperatures and different concentrations of salt, so different kinds of plankton live in them. Different kinds of plankton reflect different colors, so when you look at the ocean from the shore you see different colors in the water.\n\nThe bands and pockets of color appear because the oceans don't mix evenly.  The uneven mixture is caused by a current called the Agulhas Retroflection.
34823
Just like oxygen, hydrogen, nitrogen; NaCl is found everywhere on earth.\n\nBeing water soluable, it has been getting moved around ALOT.  When water evaporates completely, it will leave the salt behind.  The dead sea is a perect example.  Left long enough the dead sea will form a solid mass of dry salt.  Salt deposits like these can be fould all over buried the world.\n\nOne of the balancing acts with irrigation is that salt will build up in soils to point that nothing will grow.
534720
As water flows in rivers, it picks up small amounts of mineral salts from the rocks and soil of the river beds. This very-slightly salty water flows into the oceans and seas. The water in the oceans only leaves by evaporating (and the freezing of polar ice), but the salt remains dissolved in the ocean - it does not evaporate. So the remaining water gets saltier and saltier as time passes. \n\nSALINITY\nSea salts Parts per Thousand \nchloride 19.3 o/oo \nsodium 10.7 o/oo \nsulfate 2.7 o/oo \nmagnesium 1.3 o/oo \ncalcium 0.4 o/oo \npotassium 0.4 o/oo \nbicarbonate 0.15 o/oo \nbromide 0.07 o/oo \nother 0.06 o/oo \nTotal Salinity 35.08 o/oo \nThe salinity (salt content) of ocean water varies. The oceans and seas contain roughly 5 x 10 16 tons of salts. One cubic foot of average sea water contains 2.2 pounds of salt. \n\nThe oceans are about 3.5% salt (by weight). Salinity is generally reported in terms of parts per thousand (abbreviated o/oo), the number of pounds of salt per 1,000 pounds of water; the average ocean salinity is 35 o/oo. \n\nThe saltiest water is in the Red Sea and in the Persian Gulf, which have a salinity of about 40 o/oo (due to very high evaporation rates and low fresh water influx). The least salty seas are in the polar regions, where both melting polar ice and a lot of rain dilute the salinity.
781539
Salt is widely distributed in nature. It is found in solution in ocean water in concentrations of about 30 g/litre (about 4.08 oz/gal) of water, meaning that salt makes up about 3 per cent of ocean water by weight. The compound is also distributed throughout many rivers and inland lakes and seas, the concentration varying from 0.002 per cent in the Mississippi River to 30 per cent in the Dead Sea. Salt can occur as a surface crust or layer in swamps and dry lake bottoms, especially in extremely arid regions. The mineral halite, more commonly known as rock salt or massive salt, occurs in beds deposited by the dehydration of ancient bodies of salt water. The compound is constantly being formed by the action of rivers and streams on rocks containing chlorides and compounds of sodium. Salt melts at 804° C (1479° F) and begins to vaporize at temperatures just slightly above this; it has a relative density of 2.17.
221741
The density of seawater:\n\nhttp://hypertextbook.com/facts/2002/EdwardLaValley.shtml\n\nThe density of ice:\n\nhttp://www.elmhurst.edu/~chm/vchembook/122Adensityice.html\n\nThe figures for the world's volume of freshwater are available on a number of sites and in various texts.  Suffice to say that about 97% of the world's water is oceanwater, and some 80-90% of what's left over is frozen in the ice sheets.\n\n''With ice being significantly less dense than water will melted glaciers and ice mass really cause the ocean to rise? And even if that is so, would the volume of ice melting have to be incredibly dramatic to cause even a small rise?''\n\nDefinitely.  Sea ice will not contribute to rising sea level, but ice sequestered in glaciers will, because it was ultimately derived from the ocean.  The volume of melting would not have to be dramatic to make life interesting; if Greenland alone melted, that would raise sea level by some 20 feet.  A much smaller rise over the next century, of one to three feet, would still be disastrous for the most low-lying areas of the globe.
575768
No oceans are made of freshwater, unless I am mistaken. They are all made of salt water.
342985
Ocean currents can change the supply of scf level wind, and thier volume density, the fresher the water the more water vapor we would have.  Like with the effect of global warming yes, if there is too much fresh water entered into the oceans due to the melting of the sea ice at the poles, then the Thermohaline will indefinately stop, which would affect what are weather is like.  The waters in the tropics will become massively warmer and the water near the poles would be colder, and in order for the world to balance that out, it will create more hurricanes, to pick up the slack of lossing its main currents.
789602
It's also true with water going down the drain. It goes the other way in the southern hemisphere, because of the earths rotation.
427084
The density of water is greatly affected by salinity, or the salt concentration.  When salts are dissolved into pure water, the density of water increases because the salts have a greater density than the water; thus freshwater floats on salt water.  This is also why your ability to float differs between a swimming pool and an ocean.
829824
If this all was true, the waters off the EAST coast would be higher, since Earth spins toward the east. \nHowever; even the ocean has areas of higher/lower elevation, according to Topex Dynamic Ocean Topography.\nhttp://seawifs.gsfc.nasa.gov/OCEAN_PLANET/MOVIES/Topex_Dynamic_Ocean_Topography.mpg\nBut there, around NZ, the ocean does not show higher elevation; it's at a normal  level.
290700
(m)\n\nEveryone who has been to the beach knows that seawater is salty. Everyone also knows that fresh water in rain, rivers, and even ice is not salty. Why are some of Earth’s waters salty and others not? There are two clues that give us the answer. First, “fresh” water is not entirely free of dissolved salt. Even rainwater has traces of substances dissolved in it that were picked up during passage through the atmosphere. Much of this material that “washes out” of the atmosphere today is pollution, but there are also natural substances present.\n\nAs rainwater passes through soil and percolates through rocks, it dissolves some of the minerals, a process called weathering. This is the water we drink, and of course, we cannot taste the salt because its concentration is too low. Eventually, this water with its small load of dissolved minerals or salts reaches a stream and flows into lakes and the ocean. The annual addition of dissolved salts by rivers is only a tiny fraction of the total salt in the ocean. The dissolved salts carried by all the world’s rivers would equal the salt in the ocean in about 200 to 300 million years.\n\nA second clue to how the sea became salty is the presence of salt lakes such as the Great Salt Lake and the Dead Sea. Both are about 10 times saltier than seawater. Why are these lakes salty while most of the world’s lakes are not? Lakes are temporary storage areas for water. Rivers and streams bring water to the lakes, and other rivers carry water out of lakes. Thus, lakes are really only wide depressions in a river channel that have filled with water. Water flows in one end and out the other. \n\nThe Great Salt Lake, Dead Sea, and other salt lakes have no outlets. All the water that flows into these lakes escapes only by evaporation. When water evaporates, the dissolved salts are left behind. So a few lakes are salty because rivers carried salts to the lakes, the water in the lakes evaporated and the salts were left behind. After years and years of river inflow and evaporation, the salt content of the lake water built up to the present levels. The same process made the seas salty. Rivers carry dissolved salts to the ocean. Water evaporates from the oceans to fall again as rain and to feed the rivers, but the salts remain in the ocean. Because of the huge volume of the oceans, hundreds of millions of years of river input were required for the salt content to build to its present level. \n\nRivers are not the only source of dissolved salts. About twenty years ago, features on the crest of oceanic ridges were discovered that modified our view on how the sea became salty. These features, known as hydrothermal vents, represent places on the ocean floor where sea water that has seeped into the rocks of the oceanic crust, has become hotter, and has dissolved some of the minerals from the crust, now flows back into the ocean. With the hot water comes a large complement of dissolved minerals. Estimates of the amount of hydrothermal fluids now flowing from these vents indicate that the entire volume of the oceans could seep through the oceanic crust in about 10 million years. Thus, this process has a very important effect on salinity. The reactions between seawater and oceanic basalt, the rock of ocean crust, are not one-way, however; some of the dissolved salts react with the rock and are removed from the water.\n\nA final process that provides salts to the oceans is submarine volcanism, the eruption of volcanoes under water. This is similar to the previous process in that seawater is reacting with hot rock and dissolving some of the mineral constituents.\n\nWill the oceans continue to become saltier? Not likely. In fact the sea has had about the same salt content for many hundred of millions if not billions of years. The salt content has reached a steady state. Dissolved salts are being removed from seawater to form new minerals at the bottom of the ocean as fast as rivers and hydrothermal proce
968670
Water in the sea can vary in salt concentration, temperature and in ion ratios. The first two create differences in the density of the water and therefore warm / less salty (light) water floats on cold/ salty (heavy) water.\n\nSince these currents do not mix easily, different ratio's of ions in seawater can maintain their difference. These differences are created by sources of ions (vulcanic activity which can create specific ions, incoming rivers) or by the fact that certain ion concentrations (HCO3-, HSOx-) are very temperature dependent. \n\nusefull info can be found on http://www.biosbcc.net/ocean/marinesci/02ocean/swcomposition.htm