Nordic Hydrolgy, 27, 1995,35 1 -368 No p;~l-l may I)c wp~odured by any pl-occ\\ willlour cornpl~tc ~'eftlc~icc The Exchange of Water and Salt across the Drogden Sill in 0resund September 1993-November 1994 FI. Jakobsen and M.J. Lintrup Danish Hydraulic Institute, DK-2970-Herrsholm, Denmark In this paper accurate hourly time series of water and salt transport across the Drogden Sill in Bresuncl are presented for a period of more than one year. The investigation is based on nieasured current, salinity and water levels from two fixed stations in the Drogden Channel and the Flinten Channel. The water trans- port is calculated by the method outlined in Jakobsen and Castejon (1995), which is extended in thc present paper to include salt transport. The resulting water and salt transport distributions are givcn as functions of time or salinity. The data analyses show a net water discharge out of the Baltic Proper across the Drogden Sill ol. 2.5~10' m3/s and a net salt flux into the Baltic Proper of 58 tonnesis. The outflow is water with a salinity less than 12 glkg, while the inflow takes place in the interval from 12 glkg to 32 gikg. The Knudsen relations are extcnded by two equations regarding gross transport, whereby the barotropical- ly pulsating flow of changing salinity may be equated with a corresponding two- layer system of opposing residual fluxes. Introduction In the past much scientific research has aimed at determining the residual in- and outflow of water and salt in the transition area between the Baltic Sea and the North Sea based on ship measurements, sometimes combined with fixed station measure- ments, see Fig. 1. A satisfactory physical description of the Baltic Sea can be found in Svansson (1 975) and MBlki and Tamsalu (1985). Measurements in, or nearby, the Downloaded from http://iwaponline.com/hr/article-pdf/27/5/351/3133/351.pdf by guest on 16 September 2023