page_title: Pycnocline
hierarchical_section_title: Pycnocline
caption_attribution_description: English: Moon jellyfishes (Aurelia aurita) disturbing the top water layer of Gullmarn fjord at Sämstad, Lysekil Municipality, Sweden. The photo was taken on a calm, sunny morning after a rain, so it's likely that the layer is warmer water with some freshwater added. In this case that would make a thermocline coincide with a halocline and resulting in a very thin but visible pycnocline. This difference in density and the altered refractive index is what makes the water look "oily". The jellies are quite small and young, about 5–6&#160;cm (2.0–2.4&#160;in) in diameter, and since the are just below the surface and stirring up the pycnocline beneath them, that would make the layer of warmer freshwater on the fjord about 6–8&#160;cm (2.4–3.1&#160;in) thick at the time.
context_page_description: A pycnocline is the cline or layer where the density gradient is greatest within a body of water. An ocean current is generated by the forces such as breaking waves, temperature and salinity differences, wind, Coriolis effect, and tides caused by the gravitational pull of the Moon and the Sun. In addition, the physical properties in a pycnocline driven by density gradients also affect the flows and vertical profiles in the ocean. These changes can be connected to the transport of heat, salt, and nutrients through the ocean, and the pycnocline diffusion controls upwelling.
  Below the mixed layer, a stable density gradient separates the upper and lower water, hindering vertical transport. This separation has important biological effects on the ocean and the marine living organisms. However, vertical mixing across a pycnocline is a regular phenomenon in oceans, and occurs through shear-produced turbulence. Such mixing plays a key role in the transport of nutrients.
context_section_description: A pycnocline is the cline or layer where the density gradient () is greatest within a body of water. An ocean current is generated by the forces such as breaking waves, temperature and salinity differences, wind, Coriolis effect, and tides caused by the gravitational pull of the Moon and the Sun. In addition, the physical properties in a pycnocline driven by density gradients also affect the flows and vertical profiles in the ocean. These changes can be connected to the transport of heat, salt, and nutrients through the ocean, and the pycnocline diffusion controls upwelling. 
  Below the mixed layer, a stable density gradient (or pycnocline) separates the upper and lower water, hindering vertical transport. This separation has important biological effects on the ocean and the marine living organisms. However, vertical mixing across a pycnocline is a regular phenomenon in oceans, and occurs through shear-produced turbulence. Such mixing plays a key role in the transport of nutrients.
caption: Two moon jellyfish disturbing the pycnocline in the top water layer of Gullmarn fjord, Sweden
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