[dentstudent (OP)]

So the sea is salty, I think because of rock weathering and mineral release - so why doesn't a large body of water like the Great Lakes become salty?

[another_someone]

The sea is salty because the only place for the water to go when it has reached the sea is to evaporate, leaving the salt behind.

The same is true of the dead sea - with is an inland sea, but because it has no significant outflow, so there is nowhere for the slightly salty water to go except to evaporate.

The great lakes also carry a small amount of salts and minerals into the lakes, but not enough to make them appreciably salty; but the also carry most of the water out again before much of it has a chance to evaporate, so the outgoing water also carries the salt with it, whereas the evaporating water does not.

[dentstudent (OP)]

OK - that makes perfect sense! I guess the sea doesn't keep getting salty because there is always fresh water going in as it evaporates......Does this mean that the net saltiness of the sea is going to reduce as global warming increases sea level, and piles in all that fresh water from the Greenland and Canadian ice caps?

[another_someone]

OK - that makes perfect sense! I guess the sea doesn't keep getting salty because there is always fresh water going in as it evaporates......Does this mean that the net saltiness of the sea is going to reduce as global warming increases sea level, and piles in all that fresh water from the Greenland and Canadian ice caps?

It depends on whether the rate of fresh water increases faster than the rate of evaporation.

If one has global warming, one would expect an increase in the rate of evaporation due to the warmer temperatures.  If that rate of increase of evaporation is faster than increased rate of ice melt, then the sea will become saltier, and if the converse is true, then the seas will become less salty.  This may also be a regional and temporal think (I would guess that the Arctic and Antarctic seas are anyway less salty than the equatorial seas), and you may get a sudden rush of fresh water when there is a sudden breakup of one part of the ice, and then a period as the sea gets saltier as not a lot of more ice is broken off for a while.  It will also depend a lot on the nature of the mixing of waters in the seas.

[mark71]

saw the answer in a cartoon once...is because the devil poured salt into the sea...