Discussion»Statements»Rosie's Corner» What happens when all icebergs have melted? What is the rate of evaporation or does evaporation not exist in salty seas?
If they are of sea-ice, their melting will not affect the sea-level. The whole North Polar ice-cap could melt with no sea-level change as it is just floating sea-ice.
If the ice is from glaciers and terrestrial ice-sheets that are retreating (i.e. not being replenished as fast as their snouts melt) then sea-level will rise.
If this terrestrial ice is replenished by snow-fall faster than its lower edges melt, on a sufficiently large scale, sea-level falls.
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Sea-water most certainly does evaporate, leaving the salt behind. That is the source of rain and snow! The Earth's water is in a constant cycle, even if individual "bits" of water are temporarily held somewhere or broken by chemical reactions.
Sea > vapour > clouds > precipitation > rivers (including via glaciers) > back to the sea .
and;
Sea > vapour > clouds > precipitation > living organisms > excretion / respiration / decomposition > the ground or air > back into the cycle.
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Wonderful stuff, water.
One unique and beautiful physical property of water that has allowed life to exist, is that its temperature of maximum density is approximately 4ºC (depending on salinity). So as water cools below that to its freezing-point (0ºC / 32ºF for fresh, a bit lower for salt) it expands again. That makes ice less dense than the water around it, so it floats.
If water behaved like other substances, its ice would be more dense then the surrounding water, so sink; so the planet's seas would be frozen solid except for a shallow surface layer thawed by the Sun's heat. That might mean the land would be mainly arid as there would be much less water free for significant precipitation, and virtually no ocean water circulation.
The deep ocean temperature is generally at that magic 4ºC, and there are plenty of animals living down there despite the chilly temperature and permanent darkness.
It has a further property helping life. I don't know if this is unique to water, but it has a "triple point", the temperature at which it can exist in any of the three "states": as a solid, liquid or gas - ice, (fluid) water, or water-vapour. That is the 0ºC, for pure water. It is a delicate stage, taking very little stimulus to change state, but important for climate, weather and life as it means water can evaporate at quite low temperatures.
The disadvantage of ice expanding is purely one of human affairs: water-pipes, road surfaces, etc. split by the expansion of ice.
Thank you for a very thoughtful and informative reply to my question. You say seas won't rise due to melting icebergs. I read that by 2050 the seas will have risen 19 inches due to melting icebergs...I think. Now sheets of ice vs icebergs. Why aren't their properties the same and the effect of their melting the same? By 2050 we are told coastal cities will be under water due to the rising seas. So I'm a little confused. Of course I won't be here then but others will. How will they be affected? :) Do you live inland in your country or close to the ocean?
This post was edited by RosieG at March 5, 2020 1:39 AM MST
Ammonia does that too, at a much lower temperature. Saturn's moon Titan has ammonia-based "weather". It's due to the fact that both compounds are polar molecules. E99 could probably explain it better than I can.
Durdle 