Sensitivity of the Baltic Sea salinity to thefreshwater supply

Climate Research

Frank Kauker¹  H. E. Markus Meier¹ 

关键词: Baltic Sea;    Climate;    Sea-ice-ocean modeling;    Freshwater supply;    Major Baltic inflows;    Sensitivity of salinity;    Scenarios;    D-change approach;   

DOI  :  10.3354/cr024231

来源: Inter-Research Science Publishing

【 摘 要 】

ABSTRACT: The sensitivity of the Baltic Sea salinity to the freshwater supply is investigated using a 3-dimensional (3D) coupled sea-ice-ocean model. Today¹s climate is characterized by an average salinity of about 7.4‰ and a freshwater supply, inclriver runoff and net precipitation, of about 16 000 m³ s^-1. As recent results of some regional climate models have suggested a significant increase in precipitation in the Baltic catchment area due to anthropogenic climate change, inthis study the response of salinity in the Baltic Sea to changing freshwater inflow is investigated. Of special interest is the possibility of the Baltic Sea becoming a freshwater sea with 0‰ salinity in the future. Therefore, model simulations witmodified river runoff and precipitation for1902-1998 were performed. The model is forced with daily sea-level observations in the Kattegat, monthly basin-wide discharge data, and reconstructed atmospheric surface data. The reconstruction utilizes astatistical model to calculate daily sea-level pressure, and monthly surface-air temperature, dew-point temperature, precipitation, and cloud-cover fields. It is assumed that the Kattegat deepwater salinity of about 33‰ will not change regardless ofchanged freshwater supply. In most of the experiments the final stratification is almost in a steady state after 100 yr. We found that even for a freshwater supply increased by 100% compared to 1902-1998 the Baltic Sea cannot be classified as a freshwatersea. A pronounced halocline still separates the upper and lower layers in the Baltic Proper, limiting the impact of direct wind mixing to the surface layer. A calculated phase diagram suggests that the relationship between freshwater supply and averagesalinity of the final steady state is non-linear. The results of the 3D model are in agreement with an analytical steady-state model assumed to work for freshwater changes smaller than 30%. The latter model was applied in scenarios for the averagesalinity of the Baltic Sea.

【 授权许可】

Unknown