Cruise report from R/V Svea week 37, 2020

Type: Report
Author: Johan Kronsell
Published:

Summary

The surface water (0-10 m) in the northern parts of the Baltic Proper had for the season normal temperature. But in the Arkona Basin, the Bornholm Basin and the Bight of Hanö the sea surface temperature was above normal. In the Kattegat and the Skagerrak there were mostly normal sea surface temperatures. At most stations the sea surface temperature was 16-17°C. The lowest surface temperature was 15.5°C and this was at the coastal station Ref M1V1 between Öland and the main land. The sea surface salinity was still above normal seasonal values in the Baltic Proper, and was 7-8 psu. Sea surface salinity in the Kattegat and the Skagerrak was mostly normal.

Concentrations of dissolved inorganic nitrogen in the surface water (0-10m) were at most stations low, and at many stations below level of detection, which is normal for the season. Levels were above normal for the season at 5 stations, and the highest concentration was found at BCSIII-10 in the south eastern part of the Baltic Sea with just over 0.5 µmol/l. Concentrations of phosphate in the surface water were mostly normal for the season, but at one stations in the Skagerrak and in the Sound concentrations were below normal, and three stations in the Baltic Proper had concentrations above normal. Levels of silicate were in general above normal for the season in the Baltic Proper, and below normal in the Kattegat and the Skagerrak.

In the Skagerrak and the Kattegat the oxygen concentrations in the bottom water were mostly good, but at Släggö and at Anholt the concentration was below 3 ml/l. And in the Sound it was only 2.2 ml/l. In parts of the Arkona Basin and the Bornholm Basin, the Bight of Hanö and in the southeastern parts of the Baltic Proper oxygen deficiency (< 2 ml/l) was found in the bottom water. In both eastern and western Gotland Basin oxygen deficiency was found from 70 meters depth, and anoxic conditions with hydrogen sulfide present were found from 80-90 meters depth.