Isopycnals are layers within the ocean that are stratified based on their densities and can be shown as a line connecting points of a specific

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

potential density The potential density of a fluid parcel at pressure P is the density that the parcel would acquire if adiabatically brought to a reference pressure P_, often 1 bar (100 kPa). Whereas density changes with changing pressure, potential density of a f ...

on a graph. Isopycnals are often displayed graphically to help visualize "layers" of the water in the ocean or gases in the atmosphere in a similar manner to how

contour lines A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value, so that the curve joins points of equal value. It is a plane section of the three-dimensional graph ...

are used in topographic maps to help visualize

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

Types

Oceanography

Water masses in the ocean are characterized by their properties. Factors such as density, temperature, and salinity can all be used to identify these masses and their origins as well as where they are in the water column. Density plays a large role in stratifying the ocean into layers. In a body of water, as the depth increases, so does the density; water masses with the highest density are at the bottom and the lowest densities are at the top. Typically, warm freshwater is less dense than cold salty water, thus the colder water will sink below the warmer water. Isopycnals are used to display this vertical distribution of the water. Variations in temperature and salinity along isopycnals can be described with

spiciness Pungency () refers to the taste of food commonly referred to as spiciness, hotness or heat, found in foods such as chili peppers. Highly pungent tastes may be experienced as unpleasant. The term piquancy () is sometimes applied to foods with a l ...

. This creates distinguishable layers of water with differing physical properties. This phenomenon is called

stratification Stratification may refer to: Mathematics * Stratification (mathematics), any consistent assignment of numbers to predicate symbols * Data stratification in statistics Earth sciences * Stable and unstable stratification * Stratification, or st ...

. The strata are held in place by the large differences in physical and chemical properties between layers that prevent mixing.

Turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...

can disturb boundaries between the layers, causing them to bend, which causes the isopycnals to appear uneven. These boundaries are known as diapycnals (Talley, 162). The ways in which the isopycnals and diapycnal are transformed can be used by oceanographers to identify the force that caused the underwater disturbance.

Mixing

Isopycnal mixing and Diapycnal mixing work together to mix and ventilate the entire ocean. Isopycnal mixing is when surface waters moving into the interior of the ocean typically run horizontally, along the isopycnal layers, settling into their correct density-dependent layer (Talley, 67). This process is important for ventilating the ocean with oxygen. Diapycnal mixing is the movement of water by either upwelling or downwelling. This mixing is occurring vertically, across the isopycnal layer boundaries. These mixing processes are essential for nutrient distribution and the upwelling of cold bottom water. Mixing of waters of the same densities is easier than across densities which is why dipycnal mixing does not occur as frequently as isopycnal mixing

Meteorology

meteorology Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...

, isopycnals are used to display different layers of gases in the atmosphere. In the atmosphere, varying degrees of humidity, temperature, and pressure change the density of air. Isopycnals are not used in meteorology as frequently as they are in oceanography, since the density gradients observed in the atmosphere are typically gradual,
Air Pressure
', National Weather Service, 2012. Retrieved December 9, 2014 unlike in stratified bodies of water. In these cases, isopycnals are less relevant, as they do not display any substantial features.

References

* Talley, Lynne D, Pickard, George L, Emery, William J, Swift, James H, Descriptive Physical Oceanography An Introduction, Elsevier LTD., 2011

External links