Density Effects
Density variations, caused by differences in temperature and salinity, determine the positions of water layers in the ocean.
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This introduction to density gives an overview of the concepts and activities explored in this unit and describes how these investigations build an understanding of ocean literacy.
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Density is a measure of how much matter is in a given space. Density differences in water masses are determined by differences in salinity and temperature.
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Throughout the world, temperature in the ocean decreases with depth. Profiles of these temperature gradients show the stratification of water layers in the ocean.
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One method for determining salinity is by using a hydrometer. A hydrometer measures density, from which salinity can be determined if the temperature is known.
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Ocean currents are formed when water layers move. Gravitational currents are formed when water masses of different densities sink or rise due to the interactions of gravitational and buoyant forces.
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Thermohaline circulation can drive water flow in marginal seas. Circulation and stratification in estuaries is determined by the mixing of less dense river water and denser ocean water.