Earth is the only known planet with seas of liquid water on its surface. All of them have notable differences that cause the density of sea water to vary depending on several factors.
To get an idea, pure water, without salt, has a density of 1,000 kg / m3, while ocean water is 1,027 kg / m3 . To calculate this density of sea water, it is necessary to take into account three factors that imply a variability in each of them. These factors are: temperature, salinity and pressure.
Temperature
As the degrees decrease in seawater, it becomes somewhat denser. Likewise, the increase in salt within the water surface considerably increases the temperature level. For this reason, when we swim in the ocean we notice the currents below the feet and not on the surface itself. This is mainly due to the fact that the water is less dense and warmer.
Salinity
This factor depends on the minerals and chemical elements that are usually dissolved in the water. These can be sodium, sulfur, chlorine, or calcium. These minerals come from two main places : on the one hand from the rocks and on the other hand from the seabed itself.
It is a direct consequence of decomposition and organic waste found in seawater.
Pressure
The third and last factor to know the density of sea water is pressure. This translates into knowing how deep the sample of the chosen fluid is. If we get closer and closer to the bottom of the sea, the density of the liquid element will be higher . On the contrary, the closer to the surface the sample is collected, the lower the density.
In addition, the way the water circulates influences at this point. In this case it is a horizontal circulation, so it moves along with other plates of water of the same density.
The formula for the density of sea water
Therefore, knowing these three factors as keys to knowing the density of sea water, we can use a formula to calculate the final value.
Although it seems a simple process, the truth is that it is difficult to measure exactly the density of seawater since many factors intervene in the equation.
This requires collecting samples from the ocean and taking them to the laboratory. Once there, using the equation ρ = ρ (T, S, p) , and the help of an instrument known as CTD, you can know the density of seawater. Normally the result is 1.02819 Kg / L at -2 degrees, 1.02811 kg / L at 0 degrees and 1.02778 Kg / L at 4 degrees.
