Thermohaline Meaning
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.
FAQs on Thermohaline Circulation
1. What is thermohaline circulation in simple terms?
Thermohaline circulation is a large-scale ocean current system driven by differences in seawater density. This density is controlled by two main factors: temperature (thermo) and salinity (haline). Cold, salty water is denser and sinks to the deep ocean, while warmer, less salty water rises to the surface, creating a continuous, slow-moving global flow.
2. What is the main difference between thermohaline circulation and wind-driven currents?
The primary difference lies in their driving force and location. Here's a breakdown:
- Wind-Driven Currents: These are primarily horizontal movements of water in the upper 100 metres of the ocean, directly pushed by wind. They are relatively fast and form large circular patterns called gyres.
- Thermohaline Circulation: This is a much slower, density-driven flow that involves both vertical and horizontal movements, extending from the surface to the deep ocean floor. It is driven by changes in temperature and salinity, not wind.
3. Where are the key starting points for thermohaline circulation?
The process of deep water formation, which initiates the circulation, primarily occurs in a few specific high-latitude regions. The two most important locations are:
- The North Atlantic Ocean: Particularly in the seas around Greenland and Iceland, where cooling and evaporation make the water cold and salty enough to sink.
- The Antarctic Coast: Along the edge of Antarctica, especially in the Weddell Sea, where extremely cold and saline water forms and sinks to become Antarctic Bottom Water.
4. Why is thermohaline circulation often called the 'global ocean conveyor belt'?
This term is an analogy to explain its function. Like a conveyor belt, this circulation system continuously transports vast quantities of heat, salt, nutrients, and dissolved gases (like carbon dioxide) around the planet. It connects all major ocean basins, moving warm surface water towards the poles and cold deep water towards the equator, playing a crucial role in regulating Earth's climate.
5. How does climate change impact thermohaline circulation?
Climate change, specifically global warming, poses a significant threat to this circulation. The primary impact comes from the melting of polar ice sheets and glaciers. This introduces a large influx of freshwater into the North Atlantic. Since freshwater is less dense than saltwater, it dilutes the surface ocean, making it less likely to sink. This can weaken, slow down, or potentially even shut down the entire conveyor belt system.
6. What would be the major consequences if the thermohaline circulation stopped?
If the global conveyor belt were to stop, the consequences for the global climate would be severe and far-reaching. Key effects would include:
- Regional Climate Shifts: Regions like Northern Europe and North America would experience significant cooling, as the warm currents that moderate their climate would cease.
- Altered Weather Patterns: The distribution of heat across the planet would change, leading to more extreme weather events, shifts in rainfall patterns, and disruption to monsoon systems.
- Marine Ecosystem Collapse: The circulation of nutrients that supports marine life would be disrupted, impacting fisheries and the entire ocean food web.
7. What does the term 'thermohaline' itself mean?
The word 'thermohaline' is a combination of two Greek roots, which directly explains the forces that drive this type of circulation:
- Thermo: Refers to temperature.
- Haline: Refers to salinity (salt content).
