Which coastal region is where seawater and freshwater mix?

"You can't even measure the concentration of [sea] salt in the region yet, " says John Tait at the University of Reading. One way of measuring is by taking samples of what's under the sea, such as seawater or seawater from a river.

A second approach involves measuring the ratio of two types of salt- soluble nutrients in water, which is known as salinity. These ratios– measured by chemical analyses– are "the fingerprint of the ocean environment", says Tait, who thinks we can infer the composition of the sea via the ratios of some of these two types of salt.

The concentrations of these two nutrients will be higher in the eastern North Atlantic than in the south. This could indicate that there is more saline water in the region and less freshwater, which would suggest the presence of large deposits of clathrate salts– salts that form from the interaction between salts and water, but are also formed when salt is dissolved and is transported by wind and wave.

The findings are detailed in a study published in Nature Chemical Biology.