Evaporation rate and salt concentration: Hard maybe?

Question

I know that evaporation during the day increases chlorine concentration in seawater, thus as the chlorine remains and water evaporates, the evaporation rate should decrease. But temperature also increases during the day so the temperature should increase, so which has the stronger effect? Please give a source as i need confirmation.

Answer 1

I am not sure what you are asking, Saif. Sea water evaporates during the day and the night, even at temperature below freezing point. The sea contains about 3.5% of salt, a.k.a. sodium chloride. The wind tears small droplets of seawater containing salt in the air. That's why coastal stuctures are more prone to rust than inland. But the evaporation, i.e. the binding of water molecules in the air, is water only and not salt. True, this process slightly increases the salinity of the water on the surface but the constant motion of the sea mixes it pretty fast.

Because the sunlight goes deep in the water and the mass of the water is relatively important, the daily variation of temperature doesn't affect the water temperature in deep water. In any case, the evaporation of the water, i.e. liquid becoming gas, only cools down the water. This is one of the amazing facts about water: When it goes from solid (ice) to liquid, or liquid to gas; it has to take heat energy. The opposite is also true: When it goes from gas to liquid or liquid to solid, it has to give heat energy.

That's why you sweat: as your moist skin dries (water evaporates) it cools it down.

Sorry, this is from my meteorological knowledge and I have no link or source to refer to. I teach meteorology to student pilots and I have sailed all my life.

Incidentally, here is how you wash your jeans when you're on a long sailing trip: You tow it after the boat for several hours. Then you hoist in as high as possible in the mast. The water will evaporate and the salt corns will be shaken out of it as it flies like a flag. if you do it on deck level, you'll never get rid of the salt and you'll always have pants that attract water, especially during the night. .... been there, done that!