Halocline
Topic: Oceans: Hydrological Cycle, Relief of the Ocean Floor, Temperature and Salinity · NCERT: Class 11, Ch 12 "Water (Oceans)"
Meaning
A halocline is a layer in the ocean where salinity rises sharply with depth. It forms when fresher, lighter water from rivers, rain or melting ice rests on top of denser, saltier water. The two do not mix easily, so the water column forms layers. This stops nutrients and oxygen from moving up and down. A strong halocline can also keep surface water warm, because the cold water below cannot rise.
Example
In the northern Bay of Bengal, fresh water from the Ganga and Brahmaputra floats over saltier seawater, which forms a strong halocline. This limits mixing and helps keep the sea surface warm.
Don't confuse with
- Thermocline: a layer where temperature drops sharply with depth. A halocline is about salinity.
- Pycnocline: a layer where density changes sharply. Density depends on both salinity and temperature, so a halocline or a thermocline can create a pycnocline.
Related concepts
- Horizontal distribution of salinity
- Red Sea salinity
- Baltic Sea
- Mediterranean Sea salinity
- Bay of Bengal and Arabian Sea salinity