>>13766134There is about 2 billion dead weight tons of merchant ships on the ocean. This does not include the weight of the ship but let's for the sake of argument say that the ships are as heavy as that so we double the number, which would also account for all small ships and other not included. In a large oil carrier this ratio would be more like 15% and in a cargo ship maybe 33% or slightly more but not near 100% so this will give some good leeway and benefit of doubt.
4 billion tons of water is conveniently 4 billion cubic metres of water. Worlds seas have a surface area of 361 million square kilometres, or 11 cubic metres of water per square kilometre. 1 square kilometre is 1 million square metres, so 11 cubic metres of water per 1M square metres. This comes out to about 11 micrometres, or 0.011 millimetres when evenly spaced.
For comparison, sea level rise is about 3 millimetres a year. Greenland alone loses about 275 billion tons of ice a year to melting, adding to the water in the ocean.
Ships make up such a tiny fraction of oceans weight I wouldn't be surprised if land reclamation projects or even simple water construction like harbors contribute more than them.
