Intro (Micro Notes Format):
Ocean salinity refers to the concentration of dissolved salts (measured in ppt). Average salinity = 35 ppt, but it varies spatially due to multiple physical, climatic, and hydrological factors.
Factors Causing Variations in Ocean Salinity:
1. Evaporation:
- High in subtropics (20°–30° N/S) → e.g., North Atlantic = 37 ppt.
- Increases salinity by removing water, leaving salts behind.
2. Precipitation:
- High rainfall zones (e.g., equatorial belt, SE Asia coast) → lower salinity (<34 ppt).
- Dilutes ocean water.
3. River Influx:
- Coastal areas with major rivers (e.g., Amazon, Ganges) → reduced salinity.
- Freshwater inflow lowers salt concentration.
4. Ice Formation and Melting:
- Freezing increases salinity (brine rejection).
- Melting (e.g., Arctic summer) decreases salinity.
5. Ocean Currents:
- Warm currents → higher salinity (enhance evaporation).
- Cold currents → lower salinity (suppress evaporation).
6. Enclosed Seas:
- Limited exchange → high salinity (e.g., Red Sea = 41 ppt, Mediterranean = 38 ppt).
- In contrast, Baltic Sea = 10–15 ppt due to riverine input.
Multi-Dimensional Effects of Salinity Variation:
1. Ocean Circulation (Thermohaline):
- Salinity + temperature differences drive deep water currents (global conveyor belt).
- Affects global heat distribution.
2. Marine Biodiversity:
- Many species are salinity-specific (e.g., corals prefer 32–35 ppt).
- Changes affect species migration, reproduction, and survival.
3. Climate Influence:
- Salinity-driven currents regulate regional climates (e.g., warming Europe via Gulf Stream).
- Altered salinity impacts monsoons and precipitation.
4. Sea Ice Formation:
- Higher salinity lowers freezing point → affects ice formation cycles.
- Important in polar feedback mechanisms.
5. Fishing Industry:
- Influences plankton growth, fish breeding zones.
- Example: upwelling in Peru coast (cold + saline) → high fish productivity.
6. Submarine Cable & Naval Operations:
- Salinity alters acoustic properties of water.
- Affects sonar systems, undersea communication.
Conclusion:
Ocean salinity variation is a crucial driver of physical, biological, and climatic processes, shaping the planet’s hydrosphere and climate systems. Understanding it is key to marine resource management and climate resilience.
