Consider the following statements about salinity in oceans 1 The average salinity of ...........

Geography World - Water Bodies

Consider the following statements about salinity in oceans

1. The average salinity of oceans is about 35 parts per thousand.

2. The salinity of Bay of Bengal is higher than that of Arabian Sea.

3. Generally partially or wholly enclosed seas display higher salinity than the open seas where there is free mixing of ocean water.

Select the correct answer using the codes given below

1 and 2 only

2 and 3 only

1 and 3 only

2 only

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Explanation:

The salinity in oceans is mainly due to salts brought down by rivers and those added through the seepage of minerals at ridges and volcanic sites. About 77% of oceanic salinity is due to Sodium Chloride or common salt.
There are several factors that affect the salinity of oceans-
•   Rate of evaporation- The oceanic waters around 20-300 N/S have high salinity due to high rate of evaporation and low rainfalls.
•   Amount of fresh water added by rivers, precipitation and icebergs- Salinity is lower in equatorial areas due to addition of fresh water by rainfall. Also in polar regions the salinity is low due to low rate of evaporation and melting of icebergs. The seas in which large rivers discharge also have lower salinity. The salinity of Bay of Bengal is lower than that of Arabian Sea due to discharge by large rivers like Ganga, Brahmaputra Irrawaddy etc.
So much so that scientists recently discovered that the coastal areas of Bay of Bengal have a stream of fresh water flowing along the coastline during rainy season due to vast volumes of fresh waters brought down by several rivers.
•   The degree of water mixing- partially enclosed seas like red sea, Mediterranean etc have higher salinity due to lack of free mixing with oceanic waters.