that increases the salt concentration in the ocean which is actually not great and when done at scale.

I dealt with CaSO4 (calcium-sulfur salt) dumping before. It is considered fine (by DNV) as long as it not in brackish waters or too close to the shore or in most of the North Sea. It's just adding salt to salt water, salt is supposed to go there.

I guess if you were doing it at insane scales it would be best to run a pipeline out, run your seapumps harder, or have ships do the dumping. Not sure.