Browning of the Baltic Sea

This is the authors' abstract. We don't add key points for this paper.

The decreasing water transparency of the Baltic Sea over the last century has been documented by in situ measurements of the Secchi disk depth ( z SD ) as well as by satellite measurements over recent decades. While the decrease in transparency for the Baltic Sea in general has become negligible from about 2013 onwards, satellite-detected light attenuation of the violet and blue light ( k d 412) has increased, particularly from 2013 onwards. In the Gulf of Bothnia (particularly in the Bothnian Bay), eastern Gulf of Finland and eastern Gulf of Riga, k d 412 has increased significantly, indicating a dramatic increase in the concentration of colored dissolved organic matter (CDOM). These findings are partly supported by in situ CDOM data. The increase in CDOM concentration is probably due to climate change induced shifts in hydrology and greening of the land, all related to global warming. The increase in CDOM concentration and its effect on light availability may cause significant ecological changes and deterioration of the aquatic food chains.