Precipitation, such as rain or snow, decreases the salinity of seawater by diluting the salt concentration.
The Dilution Effect
When rain or snow falls over the ocean, the freshwater mixes with the saltwater. This process reduces the overall concentration of salts, making the seawater less saline or "fresher".
How Precipitation Impacts Salinity
- Dilution: The primary effect of precipitation on salinity is dilution. Freshwater from rain or snow mixes with the ocean's saltwater, decreasing the proportion of dissolved salts.
- Freshwater Input: Precipitation is a major source of freshwater input into the oceans.
- Localized Impact: The effect of precipitation on salinity is often localized. Areas that experience high rainfall tend to have lower salinity compared to areas with less precipitation.
- Long-Term Changes: Over time, consistent rainfall can lead to significant reductions in salinity in specific oceanic regions.
Examples and Practical Insights
| Scenario | Effect on Salinity |
|---|---|
| Heavy rainfall in a coastal area | Salinity decreases near the coast |
| Increased snowmelt into the ocean | Lower salinity in affected regions |
| Areas with high rates of evaporation and little rainfall | Salinity increases over time in those regions. |
The reference mentions, "Where more rain or snow falls over the ocean, it dilutes the salts in the seawater there. As a result, the water becomes fresher with time. If seawater becomes saltier, it may mean that rates of evaporation have increased or that precipitation has decreased over time."
Factors that impact Salinity
- Evaporation: High evaporation rates increase salinity by removing freshwater and concentrating the salt.
- Precipitation: As discussed above, precipitation decreases salinity by adding freshwater and diluting the salt.
