G - Introduction to Oceanography
Halocline: Halocline, vertical zone in the oceanic water column in which Pycnoclines, or layers through which water density increases rapidly with depth, . Pycnocline: Pycnocline, in oceanography, boundary separating two liquid layers of different densities. In oceans a large density difference between surface waters (or upper metres [ feet]) and haloclines. In halocline. thermoclines. Lesson 7 introduces students to the primary ocean layers, the importance of understanding all the relationships and terminology for the function of temperature and salinity, the pycnocline is a function of the thermocline and halocline. 2.
Wind-driven surface currents are restricted mostly to the ocean's uppermost m ft layer or so depending upon the depth of the pycnocline.
Ocean Motion : Background : Ocean's Vertical Structure
This is because the thickness of the surface mixed layer is typically m or less. The pycnocline acts as a porous boundary that allows some kinetic energy to penetrate into deep water.
The strongest currents generally occur in the ocean's surface layer although some surface currents such as boundary currents like the Gulf Stream discussed later can be relatively strong to depths of several hundred meters.
Surface currents are changeable, continually responding to variations in the wind, precipitation, and heating or cooling.
G115 - Introduction to Oceanography
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. 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.
The bottom layer is called the deep zone and extends from the bottom of the pycnocline to the seafloor. In this layer, temperature is varies little with depth and is very cold.
Halocline | oceanography | salonjardin.info
Salinity in the deep zone is also constant and averages about 3. Because of the cold temperatures, and to a lesser degree the salinities, we find that the deep zone has the most dense seawater. The figure below is from your text.