Editing Physical oceanography (section)

=== Density and the Pycnocline ===
The combination of temperature and salinity variations leads to changes in seawater density. Seawater density is primarily influenced by both these factors—colder, saltier water is denser than warmer, fresher water. This variation in density creates stratification in the ocean and is key to understanding ocean circulation patterns.

# '''Pycnocline''': The pycnocline is a layer within the ocean where the density increases rapidly with depth. It typically coincides with the thermocline and halocline in tropical and subtropical waters, forming a sharp boundary between the less dense surface waters and the denser deep ocean waters. This density stratification acts as a barrier to vertical mixing, limiting the exchange of heat, gases, and nutrients between the surface and deep ocean layers.
# '''Thermohaline Circulation''': Density differences drive the thermohaline circulation, also known as the global "conveyor belt," which plays a crucial role in regulating Earth's climate. Cold, dense water formed in the polar regions sinks and moves along the ocean floor toward the equator, while warmer surface waters flow poleward to replace it. This global circulation helps redistribute heat and maintains the ocean's dynamic equilibrium.
# '''Regional Variations''': In areas of upwelling or downwelling, the density structure of the water column can be disrupted. Upwelling brings cooler, nutrient-rich water to the surface, while downwelling pushes surface waters to greater depths, impacting local ecosystems and global climate.

Understanding the complex interactions between temperature, salinity, and density is essential for predicting ocean circulation patterns, climate change effects, and the health of marine ecosystems. These factors also influence marine life, as many species are sensitive to the specific temperature and salinity ranges of their habitats.<!-- This looks like a refugee from an earlier version; commenting out for now; these topics should be properly worked into the article instead; in the meantime, I've copied them to the See also section
===Density===
* [[Thermohaline circulation]] (Density-driven)
'''See also:'''
* [[Downwelling]]
* [[Hydrothermal circulation]]
* [[Ocean current]]
* [[Upwelling]]
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