Water influences salinity by either adding fresh water (decreasing it) or removing fresh water (increasing it) through various natural processes.
Water's Role in Salinity
Salinity refers to the amount of dissolved salts in a body of water, particularly the ocean. The concentration of these salts is constantly being adjusted by the movement and phase changes of water, which is the solvent for the salts. The water cycle plays a crucial role in this dynamic balance.
How Water Increases Salinity
Certain water cycle processes remove fresh water from the ocean, leaving the dissolved salts behind and thus increasing the salinity of the remaining water. According to the provided information, these salinity-raising factors include:
- Evaporation of Ocean Water: When water evaporates from the ocean surface, it turns into water vapor, which is pure water without the dissolved salts. The salts remain in the ocean, increasing the concentration of salt in the remaining liquid water.
- Formation of Sea Ice: When seawater freezes to form sea ice, most of the dissolved salts are excluded from the ice structure. The salts are pushed back into the surrounding seawater, making the water just below the ice saltier and denser.
How Water Decreases Salinity
Conversely, other water cycle processes add fresh water to the ocean, diluting the saltwater and decreasing salinity. These processes offset the salinity-raising factors and include:
- Input of Fresh Water from Rivers: Rivers collect water from land and flow into the ocean, carrying relatively low concentrations of salt compared to seawater. This continuous inflow of fresh water dilutes the ocean water near coastlines.
- Precipitation of Rain and Snow: Rain and snow falling directly onto the ocean surface are forms of fresh water. This adds pure water to the ocean, which lowers the salt concentration.
- Melting of Ice: When sea ice or icebergs (which are formed from compacted snow and are therefore fresh water) melt, they release fresh water into the ocean, diluting the saltwater.
In summary, water, through its movement and phase changes in the water cycle, acts as the primary agent affecting ocean salinity by either concentrating salts (evaporation, freezing) or diluting them (inflow, precipitation, melting).
