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Comment by asimpleusecase | Hacker News Reader

Two questions come to mind. 1) what would our world be like if the oceans were not salty? We could pump fresh water all over the globe, but are there other things that would happen at scale without the salt? 2) by the article it seems like the oceans will always increase in salinity. What is that rate of increase? Then run that model backwards was there a time when salt content was low enough for ocean water to be potable ?

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Animals, and perhaps all life, would not exist. We carry the ocean around with us in our circulatory system, from a long ago bootstrap in which some creature needed to drag part of its "home" with it when it left home.

Why? Well fresh water is pretty boring. Seawater, with all those polar ions in it, enables and facilitates all sorts of interesting (i.e. useful) chemistry.

One of the reasons we can't drink seawater is that our body needs to maintain homeostasis on the blood so the chemistry continues to work properly. If you drink a lot of seawater the kidneys can't excrete the salt fast enough. For that matter, if you drink too much fresh water the opposite happens and you die too.

Exactly. We die if we don't get enough salt. There are all sorts of mechanisms in our body that rely on it. As an engineer, I like to think it's as simple as electricity not being nearly as conductive through pure water, various osmosis processes like happens in dialysis, etc.

If the ocean's hadn't been salty, we would likely have biochemistry that doesn't rely on salt so much.. instead of just keeling over.

Life finds a way

The chemical composition of the world ocean reflects the balance of inputs from the continents (as described, from riverine input as well groundwater), atmospheric cycling, and outputs: extraction via evaporite minerals in marginal environments, weathering at the seafloor, exchange over a range of temperatures with mid-ocean ridge basalt, and precipitation of minerals (mostly in the form of biogenic carbonates such as CaCO3, biogenic silica, etc.), as well as their subsequent dissolution, and lastly the biological processes of CO2 fixation and respiration of organic carbon (including electron acceptors other than O2, such as iron, sulfate, etc.).

It is the solubility of sparingly soluble phases such as CaCO3 that controls much of the seawater composition: surface seawater is close to saturation with respect to CaCO3 (calcite, aragonite). Because halite (rock salt, NaCl) is highly soluble, seawater is, conversely, fairly concentrated with respect to these ions. Seawater must be extensively evaporated to remove the far more soluble (evaporite) minerals. Over geologic time, the composition of seawater has changed, reflecting the relative pace of the various processes listed above that deliver and remove components from solution.

Global climate would be pretty different without ocean currents driven by salinity gradients.

https://en.wikipedia.org/wiki/Thermohaline_circulation

It would surely affect settlement not just in the positive sense (more potable water) but also in the negative (people need salt to live and it wasn’t always as abundant as it is now)

Just offhand thought is the earths geology over time tends to remove salt from the ocean. An example is the Messinian Salinity Crisis when the Mediterranean sea closed off and then mostly evaporated. The result was a huge layer of salt deposited under the seabed. And the rest of the earths oceans became much less salty. Would not surprise me if plate subduction doesn't sequester salts as well.

https://www2.atmos.umd.edu/~dankd/MessinianWeb/_private/HOME...

> And the rest of the earths oceans became much less salty.

Source for that claim?

Mediterranian is still more salty than oceans because of the high evaporation rate.

https://link.springer.com/article/10.1007/s40766-023-00042-9

I guess that at the time when ocean water would have been potable it would have had to wait millions of years for an animal to come along and drink. We don’t talk about air being potable ;)

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