Do the oceans get saltier over time?

Has this had any biological impact?  There's a constant influx of salt into the ocean. But from evaporation no salt leaves. It seems to me that this would imply an increase in salt concentrations.
The salinity of the oceans fluctuates up and down to stay in a rough equilibrium. This paper (paywall) shows fluctuations for the last few thousand years. Salt does constantly trickle in from the land, but it can also be deposited through different mechanisms. For instance, the Mediterranean Sea became walled off from the Atlantic Ocean around 6 million years ago and most of its water evaporated. This created huge salt deposits. When the Atlantic eventually flooded the basin again much of this salt was covered in mud and effectively removed from the ocean. Also, plate tectonics can slowly raise sea basins and isolate them from the ocean, taking their salt with them. The Paratethys sea is an example of this.

Your idea that the salinity of the ocean could be used as a sort of geological clock does have a long history behind it. Edmund Halley, the astronomer, proposed it in 1715. And attempts to estimate the age of the Earth in the 19th and early 20th centuries based on the assumption that the sea started as fresh water and gains salt from streams and rivers at a steady rate gave estimates on the order of 100 million years. We know that these estimates are off because they didn't take into account that salt could be removed from the ocean. Sometimes you see young earth creationists still citing these numbers, either dishonestly or out of ignorance.

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