Because freezing will reduce the water content of seawater and, conversely, increase its salinity, melting ice will reduce the salinity of seawater;
The general distribution pattern of seawater salinity is that it decreases from the subtropical seas of the northern and southern hemispheres to high and low latitudes on both sides. It follows from this rule that the salinity of seawater does not decrease from the equator to the poles, that is, the distribution pattern of seawater salinity is not consistent with the latitudinal distribution pattern of seawater temperature, because the factors that affect the salinity of seawater are climatic factors. It is also affected by factors such as ocean currents, land runoff, melting ice, and whether the sea closes.
The main factors affecting salinity are precipitation. and the evaporation, ocean currents and runoff to the sea. ?
Precipitation and evaporation are factors that determine the salinity of seawater at different latitudes. Ocean currents have a significant impact on the salinity of seawater at the same latitude, and runoff to the sea has a greater impact on seawater in coastal areas of the continent. The area shown in the photo is the Bohai Sea. Isohalinity lines show that salinity in coastal areas is highest in February and is lowest in coastal areas in August. Combining the climatic characteristics and runoff conditions of this area, it can be seen that the main driver of seasonal changes in salinity in coastal areas is seasonal changes in river runoff.
In addition to the three influencing factors of precipitation and evaporation, ocean currents, runoff to the sea, melting ice and the closing and opening of sea areas, the salinity of seawater will also be affected. ?
In high latitude seas, due to freezing and melting of sea water, the same sea area will experience seasonal salinity changes in winter and summer. In winter, the temperature is low, sea water freezes and salinity is high; after spring, the seawater melts and the salinity is low. The Baltic Sea is the saltiest sea in the world and the Red Sea is the saltiest sea in the world. In addition to the influence of "climatic factors and the presence or absence of fresh water inflows from terrestrial rivers", the Baltic and Red Seas have another reason. All this is due to the fact that the maritime area is relatively closed and there is little exchange between sea water and the open sea.
Sea water and fresh water have special conditionsdifferent freezing speeds. ?
Everyone who lives by the sea has this experience. Whenever cold air arrives in winter, shallow pools on land quickly freeze into a thin layer of ice; at the end of winter, the rivers freeze, but the sea surface is still rough and wavy. Only when cold spells occur frequently and the air remains cold for a long time does sea water freeze.