The correct option is 2 only.
Explanation
Ocean salinity refers to the total content of dissolved salts in seawater. It is calculated as the amount of salt (in grams) dissolved in 1,000 grams (1 kg) of seawater and is usually expressed as parts per thousand (ppt or ‰). The horizontal distribution of salinity is influenced by evaporation, precipitation, the influx of fresh water from rivers, and ocean currents.
Statement-wise Analysis
- Statement 1 is Incorrect. The salinity for normal open ocean typically ranges between 33 ppt and 37 ppt. A range of 10 ppt to 15 ppt represents brackish water, which is found in areas with significant freshwater mixing, such as the Baltic Sea or near large river mouths, but does not characterize the open ocean.
- Statement 2 is Correct. The Red Sea experiences very high evaporation due to high temperatures and receives very little precipitation. Additionally, there is no major river influx, and its connection to the open ocean is restricted. Consequently, the salinity in the Red Sea is significantly higher, reaching as high as 41 ppt.
- Statement 3 is Incorrect. Estuaries are transition zones where fresh water from rivers mixes with salt water from the ocean. The salinity in estuaries is highly variable, ranging from 0 ppt to 35 ppt depending on the volume of river discharge and tidal action. It does not remain constant at 35 ppt.
Key Takeaway
Key Takeaway: The average salinity of the open ocean is approximately 35 ppt. High salinity (e.g., Red Sea) occurs in enclosed seas with high evaporation and low freshwater influx, while low or variable salinity occurs in estuaries and areas with heavy precipitation or river drainage.