PILOTAGE PRE-PLANNING GUIDE
areas, this channel is no wider than 0,26 nautical miles.
The channel through Lilllebelt is even trickier with a depth of less than 20m, and
the Sound is “blocked” at Drogden, where the depth is a mere 8m. In addition, the
channel at Drogden is no wider than 0,15 nautical miles.
The ingress of fresh water into the Baltic Sea is considerable, causing a strong
outwards brackish surface current through the inner Danish waters, while simultaneously
transporting saliferous water from the North Sea towards the Baltic Sea
through the current in the bottom layers.
The transition between the two bodies of water is known as the thermocline.
Owing to friction, some blending of the two layers will occur, as a result of which
the salinity of the surface water will increase gradually from the Baltic Sea towards
the North Sea, while the salinity along the bottom layer will decrease gradually
towards the Baltic Sea. However, this two-layer current is rather sensitive to effects
of wind, as well as seasonality.
When subjected to major effects of wind, significant changes in water levels between
Kattegat and eastern part of the Baltic Sea can occur, fluctuating as much as
±0,8 m due to the waters being compressed by wind. This creates a surface inclination,
resulting in a combined transport of water either northbound or southbound,
depending on the direction of the wind. The speed of the current is increased,
and can reach as much as 2 m/s in the Belt. Changes in water levels owing to tidal
waters, are most significant at the entrance to the North Sea (1-2 m), and least at the
entrance to the Baltic Sea (0,1m)
Temperature conditions are regulated by the exchange of heat towards the atmosphere,
as a result of which the average surface temperature in February is fluctuating
between 0-2°C, and is about 18 °C come August, while the bottom tempera-
ture is 4°C and 12°C respectively.
(Erik Buch: Denmark – inner waters extract from ”Den Store Danske”, published by
Gyldendal, translated by DanPilot)
Routes and fairways in Danish waters are marked according to IALA A.