Oxygen in the gulf of Finland and the role of major Baltic inflows: a modelling experiment

During recent decades near-bottom hypoxia and anoxia became common in the Gulf of Finland (GoF), even though nutrient discharge from land has declined. Since the beginning of the 1990s, after a long stagnant period, several strong saline water inflows to the Baltic Sea occurred. Consequences of these events on oxygen dynamics in the GoF were studied with the aid of a coupled hydrodynamic-biogeochemical model. After the model was set up to reproduce ecohydrodynamic conditions in the Baltic Sea since 1990, an experimental run was performed, without sea-level variations at the open boundary. This does exclude one of the most important factors causing barotropic inflows to the Baltic Sea. Our main results showed that in the absence of inflows vertical salinity stratification in the GoF decreases, which improves oxygenation of deep layers. On the other hand, in case of inflows from the Baltic Proper to the GoF, less salty, but anoxic water is brought in. However, due to a weaker stratification, oxic conditions in the GoF restore rather quickly. Mechanisms responsible for the exchange between Baltic Proper and the GoF are further analysed. The results confirm that during recent decades the major Baltic inflows had a distinct influence on the near-bottom oxygen dynamics in the GoF. This raises a question of the potential impact of inflows on the GoF environment in the future, especially in combination with ecosystem management actions and climate change.

LESSIN Gennadi;  STIPS Adolf; 

2014-01-30

University of Klaipeda

JRC83821

978-9986-31-417-2,   

http://corpi.ku.lt/bssc2013/,    https://publications.jrc.ec.europa.eu/repository/handle/JRC83821,