Danish Straits

Inflow of river water into the Baltic Sea exceeds evaporation by approximately 500 km year , whrlelOOO km year leaves the Baltic Sea as surface water to the Kattegat. This means that 500 km year of saltier water enters the Baltic Sea at deeper levels (Stigebrandt, 2001). The net N outflow is 100—140 kt N year (Larsson et al, 1985 Wulff et al, 1990, 2001). We will use 150 kt N year for our N budget. The N loss through the Danish Straits and the Oresund is on the order of 10% of the total N load to the Baltic Sea (see below). Thus 90% of the N load is retained in the system. 

Soskin, I. M., 1959. The salt exchange across the Danish Straits and its influence on the long-term variations in salinity of the Baltic Sea (in Russian). Tmdy Gosudarstvennovo Okeanograficeskovo Instituta (GOIN), 37, 34 41. 

The quality of numerical simulations is limited by the horizontal and vertical model resolution. An obvious aspect of enhanced model resolution is the better representation of the bathymetry. Especially the structured coastline of the Danish Straits and the sills between the basins of the Baltic Sea are represented more accurately. Another aspect is the representation of processes with small characteristic dynamic scales in the model. Although in many cases details on unresolved processes are not needed, parameterizations for such processes are sources of numerical uncertainty. Enhanced model resolution means less parameterization and the model dynamics is represented preferably by the hydrodynamic equations. 

Sayin, E., Krauss, W., 1996. A numerical study of the water exchange through the Danish Straits. Tellus, 48A, 324-341. 

The surface area of the inner Baltic Sea, bordered at the bottlenecks of the Danish Straits, amounts toA = 382 486 km if computed using RANGS shorelines on the WGS-84 ellipsoid (Hagen and Feistel, 2001), Equation 20.10. The absolute maximum uncertainty of the sea surface is about 10%, while the likely uncertainty lies in the range between 0.1% and 1 %. The length of the border line enclosing this surface area computed at the RANGS resolution of about 100 m is about L = 70 000 km. 

The decay time of 10 days is characteristic for the linear response of the Baltic fill level with respect to changes of the level in the Kattegat, resulting from the flow resistance of the narrow and shallow Danish Straits (Chapter 2.2.2). 

Phases of a rapidly and continuously rising Landsort level are of particular interest since their physical cause is always an intense inflow from the Kattegat through the Danish Straits. With the empirical approximation formula... 

The sea-level difference between Hornbsk and Gedser and the related pressure gradient along the Danish Straits is a appropriate measure for the water exchange between the Kattegat and the Baltic Proper. In particular, it is the chief driving force for Major Baltic Inflow events, see Chapter 10. With the actual time series, an almost gap-free, continuous record of these events between 1891 and 2005 has become available, see Section 20.3.6. A total of 915 245 valid difference values are provided in the file Diff H G.asc. The mean difference is... 

For more details of the transport through the Danish Straits, see, for examples. Chapter 2 and Chapter 10 of this book, or the publications of Thiel (1938), Hela(1944), Stigebrandt (1976), Lass et al. (1987), Gustafsson (2000), Mattson (2003). 

FIG. 9.17. Left, technique for finding leaks in pipes. Right, technique for measuring stream lines in the strait of Oresund. (Courtesy Danish Isotope Center.)... 

Fig. 42.9 Diagram showing the traffic measured by vehicles per year 1990-2008 crossing the straits around the Danish island of Zealand...

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