Ocean Motion : Background : Ocean's Vertical Structure
What's the Difference Between a Thermocline and a Halocline? the oceans, more so in colder regions where cold water with a lower salinity. The water in the ocean or the sea forms layers acc is a function of temperature and salinity, the pycnocline is a function of the thermocline and halocline. What is the relationship between density and relative density?. Relationship between pycnocline, halocline, and thermocline pH of the ocean Relationship between carbon dioxide and ocean pH Group 7- Pirates!.
Stirring of surface waters by the wind produces a well-mixed layer of uniform or nearly uniform density. For this reason, the ocean surface is called the mixed layer.
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We know most about the mixed layer because ships, aircraft, and Earth-orbiting satellites can readily monitor it. Recall that cold water is denser than warm water and salty water is denser than fresh water.
Where a decline in temperature with depth is responsible for the increase in density with depth, the pycnocline is also a thermocline.
On the other hand, if an increase in salinity is responsible for the increase in density with depth, the pycnocline is also a halocline. Typically, the pycnocline extends to a depth of to m to ft.
However, in middle latitudes seasonal pycnoclines may develop within the mixed layer. The dark, cold deep layer below the pycnocline accounts for most of the ocean's mass.
Temperature and salinity directly influence density. In general, cold temperatures and increases in salinity act to increase seawater density. Conversely, warm temperatures and decreases in salinity act to decrease seawater density. The middle layer, as defined by water density, is called the pycnocline.
The pycnocline is an area where density changes rapidly with depth — from the top to the bottom of this layer density changes dramatically. This rapid change in density is directly related to the rapid change in temperature thermocline and salinity halocline in this layer.
Pycnocline | oceanography | dayline.info
The bottom layer is called the deep zone and extends from the bottom of the pycnocline to the seafloor. This has often been referred to as diurnal or diel vertical migration. The vertical distance travelled over 24 hours varies, generally being greater among larger species and better swimmers.
But even small copepods may migrate several hundred meters twice in a hour period, and stronger swimmers like euphausiids and pelagic shrimp may travel m or more.
However, phytoplankton and zooplankton capable of diel vertical migration are often concentrated in the pycnocline. Stability[ edit ] Pycnoclines become unstable when their Richardson number drops below 0. The Richardson number is a dimensionless value expressing the ratio of potential to kinetic energy. This ratio drops below 0. This can produce Kelvin-Helmholtz instabilityresulting in a turbulence which leads to mixing.