The influence of seasonal and year-to-year variability of water discharge from the Lake Ladoga—Neva River system on the salinity regime of the Baltic Sea

Abstract

The study is based on multi-year monthly and yearly averaged time series of the Neva River discharge, monthly salinity observations from near-shore hydrographie and hydrometeorological stations in the Gulf of Finland, and several years of data from international seasonal salinity observations in the open region of NE Baltic Sea. There is a good coherence between seasonal variations of the Neva River flow and the salinity regime in the upper layer of the Baltic Sea. Near the shores periods of low, normal and high salinity correspond to the periods of high, normal and low river runoff, and the same trends are observed with some time lag in the open parts of the Sea as well. The impacts of the Neva River discharge oscillations on salinity of the Gulf of Finland surface waters are analyzed in terms of time regression probability models. The obtained river flow-marine salinity transfer functions summarize well the observation data on both multiannual and seasonal scales of variability. Some seasonal periods with different anomalies of the influence are distinguished.