Unfortunately the seas of the earth are not smooth, in fact sea level is different in every place on earth, depending upon wind, tidal state, and the earths gravitational pull.
In addition there is that menacing issue of global warming, a big factor in our now constantly rising sea levels. Yet there is something else.
As you well may know, this global warming problem is to do with the glaciers melting, but there is more to it then that. More water will leave the poles then there is in the glaciers themselves, the question is, Where is that extra water coming from?
The answer is the bumpy sea levels, the water is already there, the seas at both poles are extremely deep, but the earth’s gravity isn’t strong enough to hold all of the extra water in its place, so there is some other force acting on the water. Actually it’s still gravity. As you know, the poles are covered in ice sheets, ice fields and glaciers. These are the source of the extra force.
The ice sheets at both poles are simply so massive, that they have pulled in the seas and oceans of the world, this excessive gravity means water is stacked extremely highly around the poles, leaving less water about the equator. When glaciers are gone, so is that gravity and we will all be visited by a not insignificant amount of extra water.
So let’s try to avoid melting the glaciers shall we?