Question

At area 1, a stream empties into the ocean. At area 2, precipitation enters the ocean in the form of rainfall. At area 3, evaporation takes place at the ocean’s surface. In which areas does the salinity of the ocean decrease?

Answer 1

The salinity of the ocean decreases at area 1, where a stream enters the ocean, and at area 2, where rainfall adds fresh water to the ocean. However, salinity does not decrease at area 3, where evaporation occurs.

Step-by-step explanation:

The salinity of the ocean decreases in areas where freshwater is added. At area 1, where a stream empties into the ocean, salinity decreases due to the influx of stream water, which is generally less saline than ocean water. Similarly, at area 2, when precipitation in the form of rainfall enters the ocean, it dilutes the salinity because rainwater has a very low concentration of salts compared to seawater.

However, at area 3, evaporation occurs and only pure water evaporates, leaving the salts behind, thus increasing the ocean's salinity. Therefore, the salinity decreases at areas 1 and 2, but not at area 3. It is essential to note that the water cycle involves the movement of water from the land and oceans into the atmosphere by evaporation or sublimation, where it condenses into clouds and eventually falls as precipitation, completing the cycle when surface or groundwater reenters the ocean.

Answer 2

Evaporation of ocean water and formation of sea ice both increase the salinity of the ocean. However these "salinity raising" factors are continually counterbalanced by processes that decrease salinity such as the continuous input of fresh water from rivers, precipitation of rain and snow, and melting of ice.