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.