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Comment by matte_black | Hacker News Reader

Couldn’t it be fairly trivial to raise the salinity? We have tons of salt. Enough at least to kick the can further down the road.

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Approximate annual world salt production: 0.3 billion metric tons

Approximate salt content of the Atlantic Ocean: 11,000,000 billion metric tons

The question was not if we produce enough salt to bring a completely desalinated Atlantic ocean back up to normal Atlantic salinity.

It was whether we can produce enough to bring the fresh water that is being added from melting ice up to normal Atlantic salinity.

And the answer is that if we turned all of our energy to salt production, it wouldn’t even be a drop in the ocean, and our efforts would of course liberate more CO2 and contribute to global warming. Of all the possible ways we could geoengineer (all of them bad ideas frankly) this has to be one of the worst, least effective, most limited, and least likely to succeed.

If we’re going to hasten our demise, we might as well try sulfate aerosols or something with a more global effect. We’d still end up killing ourselves, but at least it wouldn’t be quite so much like trying to get a sailboat to move by blowing on the sails.

By my rudimentary estimation (based on numbers from https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/grl... Figure 3) I believe the annual ice melt in the Arctic each year is approximately 10,000 km^3 of ice. Let's assume all of it flows into the Atlantic. Remove 10% of that volume to approximate the liquid volume of the ice, then convert to kilograms of water = 9x10^15 kg. Average ocean salinity is 35g of salt to 1kg of water. That comes out to ~3.15*10^14 (315 trillion) kg of salt. You can pick a percentage that flows into the Atlantic, but it would still require on the order of trillions of kilograms of salt.

Where exactly do you think we get our tonnes of salt? Some of it is mined but a lot of it comes from the oceans in the first place.

Joking, right? If not, I’ll match your talent for understatement with my own: the ocean is very big.

Big is still not infinite.

There must be some quantity of salt we can dump a year to raise salinity. We should be rigorous, and find out what that quantity is. If we can change a climate, we can change an ocean.

The assumption there is a feasible application of something in a location to remediate a world wide problem is attractive but I think built on faulty logic. To try an analogy, gluing a broken cup back together doesn't make it never have broken.

Yes, we probably can re-salinate a flow to attempt to alter its dynamics. We'd also have altered its salinity profile in ways which have repercussions on e.g. cod fisheries, or krill, or other things. Thats the problem with complex biological systems with lots of interrelated parts: they don't reverse with simple tweaks because once you change one part, you change lots of parts in unexpected ways.

(I did once study this stuff back in the 80s and was very bad at it, but what I recall of even two-actor predator-prey relationships is that they are remarkably complex, cyclical, and do not just return to the same stable place if you alter them trivially. I believe this is probably even more true for physical systems like weather and climate)

I suspect that like most “magic” solutions to environmental problems, this would cost significantly more than just reducing CO2 emissions.

While you are right that reducing CO2 emissions is a must, I'm uncertain if we don't have to actively remove it as well. If it's not already too late anyway. With the methane hydrate already on the move...

1/100 of 1% of the world's oceans is a cube 32 miles on each side [0]. This volume of salt would weigh 317 billion tons [1]. World commercial production is .25 billion tons of salt [2].

So, to raise salinity by .01%, we'd need 1268 years of normal production (plus some when you exclude sea-water extraction).

[0] http://www.wolframalpha.com/input/?i=(volume+of+the+world%27...

[1] http://www.wolframalpha.com/input/?i=31956+cubic+miles+of+sa...

[2] http://www.saltinstitute.org/salt-101/production-industry/

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