Thermohaline Circulation

The term thermohaline circulation is related to oceanography. Oceanography refers to the study of the physical, chemical, biological and historical properties of the ocean. Thermohaline circulation is a phenomenon in which the circulation of the component of oceanic water takes place due to temperature as well as salinity gradient. Thermohaline circulation is also known as Global Ocean Conveyor or Great Ocean Conveyor Belt as it controls the circulation components of ocean water worldwide. Thermohaline circulation suggests the replacement of surface seawater with seawater at depth. Thus it indicates the vertical flow of seawater from surface to bottom and such kind of flow is very slow.

What is Thermohaline Circulation?

To define thermohaline meaning, the term thermohaline can be divided into two parts “thermo” and “haline” which refer to temperature and salt content respectively. Thus the term thermohaline circulation indicates the involvement of temperature and salinity with this oceanic phenomenon.  Thermohaline circulation is a slow process but it involves a movement of huge amounts of water that carries heat, salts and other nutrients of seawater.

Such an ocean conveyor belt makes the warmer surface seawaters move from subtropics to poleward.

Characteristics of Thermohaline Circulation

Oceanic circulation can be divided into two kinds: wind-driven circulation and thermohaline circulation. Wind-driven circulation involves the horizontal movement of surface seawater with the help of wind current and it generates large gyres on the ocean. In contrast, thermohaline circulation is much sluggish and involves the vertical movement of seawater predominantly. It is observed that such circulation has a typical speed of 1 centimetre per second but it involves a movement of huge amounts of water that carries heat, salts and other nutrients of seawater. 

The concentration of seawater largely depends on the temperature and salt content of water. Concentration decreases with an increase in temperature and a decrease in the salt content of water in that particular region. Thus temperature and salinity control such kind of ocean conveyor belt from one location to another.

Basis of Thermohaline Circulation

Temperature and salinity are the main driving force of such circulation of seawater. During the winter season, the surface water becomes denser due to cooling and net evaporation that is why it sinks to the deeper region of the ocean and spreads slowly. Seawater at depth replaces the surface water that sinks. That is how the thermohaline circulation takes place. Henry Stommel and Arnold Arons in 1960 first developed the theory of thermohaline circulation pattern.

Sometimes temperature difference makes such kind of flow of seawater in a horizontal direction also. For example, warmer surface seawaters move from subtropics to poleward which controls the climate of Iceland and other coastal areas of Europe.

Global Warming and Thermohaline Circulation

Global warming is a phenomenon that increases the average temperature of the earth due to the excessive addition of heat-trapping greenhouse gases like carbon dioxide, methane, nitrogen dioxide, etc. Global warming is the major reason for worldwide climate change. According to scientists, global warming can impose a major impact on the Great Ocean Conveyor Belt. Due to the increase of the average global temperature the glacier and the ice sheets in the polar region are melting and creating a huge influx of freshwater in the ocean. 

Freshwater addition makes the surface seawater less dense as a result the sinking process of surface water is inhibited. Thus such a phenomenon can even shut down oceanic thermohaline circulation. Scientists predict that such a stoppage of thermohaline circulation can trigger colder conditions in polar regions. Moreover, a stoppage in circulation makes a large impact on the oceanic ecosystem due to the stoppage of the nutrient cycle as well.

Did You Know?

1.Henry Stommel and Arnold Arons in 1960 first developed the theory of thermohaline circulation pattern.

2.The term thermohaline can be divided into two parts “thermo” and “haline” which refer to temperature and salt content respectively.

3.Sometimes temperature difference makes such kind of flow of seawater in a horizontal direction also. For example, warmer surface seawaters move from subtropics to poleward which controls the climate of Iceland and other coastal areas of Europe.

Conclusion

Thermohaline circulation is an oceanic phenomenon that involves the vertical flow of seawater in a bulk due to the temperature and salinity gradient. Such a slow bulk flow helps in the circulation of nutrients and other biological matters of seawater. Thus thermohaline circulation on nutrient cycle and coastal climate.