Our magnetosphere protects the atmosphere from solar winds "blowing" water from Earth so Earth doesn't lose that much water.
Water finds its own level. The atmosphere always finds its own level with regard to water vapor as well. As we have all experience, it doesn't take that much for a bunch of water to fall from the sky and make its journey to the ocean. Gravity will pull ice and water to the oceans. The amount in the ocean and its precise shape and depth depends on many factors from plates moving (vertically and horizontally), to oceans warming and cooling, to ice on land melting, etc. Changes in temperature will change the volume of water and since the ocean is so massive, a small change will have a noticeable affect.
When we had the glaciers over much of North America, ocean levels were many hundreds of feet lower. Since then, ocean levels have risen significantly as the glaciers retreated toward the north. We have been in a minor warming interval for several hundred years now since the end of the Little Ice Age, and the sea level has been rising slowly. Only a portion of that may be from human emissions of CO2. Some would try to push their political agenda by pretending that any change in sea level is due to humans and therefore we need to give money and power to them but that isn't science and it would be really short sighted for people to go along. In fact, ocean levels are not static over the entire world and they are less so locally because land rises and falls depending on where you are. Land isn't as static (meaning it moves) as many believe.
Ice sublimates which is like evaporation.