system
Given the following post, respond as if you're commenting on Reddit:
human
If all the polar ice caps melted, would the ocean become less salty?
gpt
Physical oceanographer here.
There was an article published in Science 7  years ago answering this exact  a question using Paleo oceanographic  evidence from the last deglaciation (Synchronous deglacial overturning and water mass source changes by Natalie Roberts and others).


Deglaciation does, by simple math make the world's oceans less salty but not in the way you think it would. It takes gargantuan amounts of energy to mix water masses with different properties, so instead of the entire ocean reducing its spicyness (salt concentrations), you'd see certain currents take the biggest hits while others remain pretty much unchanged. 

Now, the ocean currents that have been shown to be most affected by current and past deglaciation are those feeding deep, cold water to the world's oceans (water can only sink to the bottom of the ocean near Antarctica and Greenland). In case of a total deglaciation, this supply would stop, meaning that:

 **The rates at which deep water resurfaces and that at which surface water sinks to abyssal levels would reduce drastically. Freshwater, the article finds, would remain in the upper ocean and drive overturning there.**

In short, a deglaciation partially stops the exchange of energy, salt, and heat between the deep and upper ocean, leaving only topography-driven and tidally-aided sources for turbulence to cause 'communication' between these two layers. This is pretty much how lakes work (no tides though, but being smaller, lakes can have their bottom layers accelerated by wind under some special conditions), so oceans would become much more similar to them. This is by no means that currents would stop (wind and tides would remain stirring everything up), but it is only the deep/upper water exchange that would pretty much disappear.