Sea surface salinity, global map. The salinity (salt content) of the surface of the oceans depends on factors such as sea surface temperature (which determines evaporation), the effect of the wind, and the addition of fresh water from rivers, rain, and melting sea and pack ice. Here, lighter green indicates higher salinity, and darker green lower salinity. The Atlantic Ocean (centre) is highly saline because of water flowing in from the Mediterranean Sea. Areas of low salinity include the mouths of the Mississippi and Amazon rivers. The data used in this map is from the World Ocean Atlas 2005.