The horizontal distribution of atmospheric pressure across the Earth's surface is controlled mainly by air temperature, the amount of water vapour present and the Earth's rotation.

Higher air temperature expands the air column and lowers surface pressure, while cooler dense air raises it; moist air containing water vapour is lighter than dry air of the same temperature, so it also reduces pressure.

The Earth's rotation deflects air through the Coriolis force and helps organise the pressure belts into a zonal pattern.

Ocean salinity acts on sea-water density and ocean circulation, but it is not a direct control on the horizontal spread of atmospheric pressure.

Hence, the factor that does NOT influence the horizontal distribution of air pressure is ocean salinity.