Anomalies in the physical and chemical structure of the Gdańsk Deep caused by groundwater seepage

Seepage of freshwater into the near-bottom layer (ca 100m depth) of the Gdansk Deep was reported during short-term studies on the variations of concentration of chemical compounds and the stratification of this basin. As a result, the salinity fell to below 1 PSU and the temperature rose from 5 to ca 7.5oC in this layer; further consequences were changes in the chemical and hydrological stratification throughout the water column. Directly above the area of seepage there was a zone of powerful turbulent convection where the temperature-salinity Rayleigh number was of the order of 10^16. Large quantities of suspended matter and poorly oxygenated deep waters were carried by the convection current from below the halocline up to the sea surface. This seepage of groundwaters is probably a continual and not an intermittent phenomenon.