The autumnal breakdown of these regions in stratified lakes leads to upwelling of nutrient-rich water from the cold depths that mixes with the warmer surface layer.
They aren't determined by chemical composition, but the energy cost to adiabatically destroy one of these regions is measured by the Schmidt stability index. Sonar reflects off these regions due to the negative sound speed gradient caused by their sudden density changes. They're not found on the surface, but these regions can support standing waves called seiches ("SAY-shiz"). In the oceans, these regions are nonexistent at polar latitudes, while they are found within the mesopelagic zone in the tropics. These regions separate the epilimnion from the hypolimnion, and they often coincide with the pycnocline ("PICK-no-clyne"). The autumnal breakdown of these regions in stratified lakes leads to upwelling of nutrient-rich water from the cold depths that mixes with the warmer surface layer. For 10 points, name these regions over which water temperature changes rapidly with depth.
They aren't determined by chemical composition, but the energy cost to adiabatically destroy one of these regions is measured by the Schmidt stability index.
thermoclines [or metalimnions; accept pycnocline until “density changes,” and prompt on pycnocline afterward; prompt on thermal layers or density layers or clines] &lt;Other Science (Earth Science)&gt;