If seawater were incompressible, each cubic centimetre of water in the water column would expand, and density values at all depths would be equal. Increasing density values demonstrate the compressibility of seawater under the tremendous pressures present in the deep ocean. Values associated with the change in seawater density with depth are listed in the table.ĭensity changes with depth (seawater 35 parts per thousand and 0 ☌) (One decibar is one-tenth of a bar, which in turn is equal to 10 5 newtons per square metre.) Because a one-metre (three-foot) column of seawater produces a pressure of about one decibar (0.1 atmosphere), the pressure in decibars is approximately equal to the depth in metres. The relationship between pressure and density is demonstrated by observing the effect of pressure on the density of seawater at 35 psu and 0 ☌. The σ t of seawater increases with increasing salinity and decreasing temperature. The σ t has no units and is an abbreviated density of seawater controlled by salinity and temperature only. This value is obtained by subtracting 1.0 from the density and multiplying the remainder by 1,000. These two factors led oceanographers to adopt a density unit called sigma- t ( σ t). Also, the pressure effect can be neglected in many instances by using potential temperature. Because oceanographers require density measurements to be accurate to the fifth decimal place, manipulation of the data requires writing many numbers to record each measurement. The density of seawater is a function of temperature, salinity, and pressure. In oceanography the density of seawater has been expressed historically in grams per cubic centimetre. The density of a material is given in units of mass per unit volume and expressed in kilograms per cubic metre in the SI system of units. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.
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