Key physical parameters

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Key physical parameters


Observing the physical state of the sea

Physical parameters are characterising the basic conditions for marine life and allow conclusions about the circulation in the ocean. Physical parameters, for example, indicate how warm or cold the water is or how much salt is dissolved in the ocean. The salinity of sea water specifies how many grams of salt are dissolved in one kg of water. An old unit for salinity is per mille, but the current unit is the dimensionless property “practical salinity unit” (psu). In the North Sea surface salinity varies between values of 35 at the northern boundary to the Atlantic Ocean and values less than 30 in the German Bight. Surface salinities in the Baltic Sea range between 30 in the Skagerrak to less than 5 in the Gulf of Finnland and the northern Gulf of Bothnia.

Another important physical parameter is the density (weight) of sea water. The density depends on temperature, salinity, and pressure of the water. The pressure increases approximately by 1 dbar (1bar = 105Pa) for every meter of water depth. Density increases with increasing pressure and salinity and with decreasing temperature. Differences in sea water density are very important because they drive currents in the ocean, the so-called thermohaline circulation: Heavy water sinks to greater depth and light water rises Other parameters describe movements of the ocean. They comprise for example the speed and direction of currents  and information on the height and direction of the sea state . Currents are either driven by winds at the sea surface, density differences in the ocean or tides, i.e. the gravitational attraction of sun and moon.

Of special importance for the navigation is ice coverage in winter time – especially for the Baltic Sea. The BSH publishes  weekly ice reports and ice maps , which describe the extend and intensity of ice coverage.

Geological Parameters  are of importance for the utilisation of the sea floor as a natural resource, as for sand and gravel extraction. Knowledge of these parameters is also needed during the construction of buildings at the coast or in the sea. The list of parameters includes the sediment distribution, thickness of the sediment and grain size among other properties of the sea floor.


 © 2018 Bundesamt für Seeschifffahrt und Hydrographie Last Update: Apr 19, 2013 6:00:05 PM  
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