Sensitivity of Baltic Sea salinity to large perturbations in climate

Abstract

Potential future changes in the salinity of the Baltic Sea must be included in safety assessments of nuclear waste repositories. The salinity affects the potential recipient ecosystems, water turnover along the coast, as well as the groundwater hydrology and groundwater chemistry. The time-scales of nuclear waste repositories are extremely long, and climate forecasts must therefore encompass extreme variations. This study presents a model that enables computation of Baltic Sea salinity for different sea level positions and freshwater supplies, thus making it possible to assess the impact of a given climatic change. A modest rise in global sea level (+ 1 m) would lead to a salinity increase from 8 to 9 in the southern Baltic Proper. An increase in the freshwater supply by about 2000 m3 s-1 (approximately + 10%) would result in a similar salinity change. Further, a sea level drop of about 5 m or an increase in the freshwater supply by a factor of 3 would reduce the salinity in the southern Baltic Proper to <1, i.e. large parts of the Baltic would become limnic. A 50% decrease in freshwater supply would double the salinity in the southern Baltic Proper to about 15; the effect is more pronounced in the Bothnian Sea and Bothnian Bay, where the salinity would increase from 6 to 13 and from 3.5 to 10, respectively. © Inter-Research 2004.