What is the reason for the difference in the salinity of sea water at different latitudes

The temperature and evaporation rates determine the salinity of seawater and its variations at different latitudes.

Explanation:

The seawater is saline. This basically means that it contains salt in it in amounts that are high enough to make it salty. The water in the sea is saline because of the enormous amounts of salt on the rocks that are covered with seawater, so the salt dissolves into the water, mixes with it, and gives its salinity. The salinity is not the same everywhere though and there are great variations.

The seawater tends to have the highest salinity near the in the lower latitudes, thus at the tropical areas, while the salinity is the smallest at the high latitudes, thus around the poles. This is due to the difference in temperature and based on it, rates of evaporation. At the lower latitudes, the temperatures are constantly high so the evaporation rates are constantly high as well. This leads to a higher concentration of salt in the water. In the higher latitudes, the temperature is very low so the evaporation is very low as well. This leads to a smaller concentration of salt in the water.

it is very hard for the climatologists to precisely predict how will the global temperatures be changing so there's lots of models, some of which differ significantly, this is due to multiple factors, and probably the most important is the human activity.

humans have been a key factor in climate change around the globe since the start of the industrial revolution, and in the past few decades the consequences are becoming more obvious. there's lots of emission of pollutants in the atmosphere as well as changing the environment on the surface itself, so it's really hard to predict how will that go in the future because there's some countries that are reducing the damage and are going towards green energy, while others are stubbornly continuing with pollution and damages to the environment.