Oxygen Survey in the Baltic Sea 2021 - Extent of Anoxia and Hypoxia, 1960-2021
Hansson, Martin (Creator), Viktorsson, Lena (Creator)
A climatological atlas of the oxygen situation in the deep water of the Baltic Sea was first published in 2011 in SMHI Report Oceanography No 42. Since 2011, annual updates have been made as additional data have been reported to the International Council for the Exploration of the Sea (ICES) data centre. In this report the results for 2020 have been updated and the preliminary results for 2021 are presented. Oxygen data from 2021 have been collected from various sources such as international ICES coordinated trawl survey, national monitoring programmes and research projects with contributions from Poland, Estonia, Latvia, Denmark, Sweden and Finland.For the autumn period each profile in the dataset was examined for the occurrence of hypoxia (oxygen deficiency) and anoxia (total absence of oxygen). The depths of onset of hypoxia and anoxia were then interpolated between sampling stations producing two surfaces representing the depths at which hypoxic and anoxic conditions respectively are found. The volume and area of hypoxia and anoxia were then calculated and the results transferred to maps and diagrams to visualize the annual autumn oxygen situation during the analysed period.The updated results for 2020 and the preliminary results for 2021 show that the severe oxygen conditions in the Baltic Proper after the regime shift in 1999 continues. Levels of anoxia decreased somewhat compared to the record years 2018-2019, while the extent of hypoxia remained largely unchanged. The decreased in anoxia was seen in the southern Baltic Proper and in the Gulf of Finland.The hydrogen sulphide that had disappeared from the Eastern and Northern Gotland Basin due to the inflows in 2014-2016 continues to increase in the deep water. No major inflow has occurred during 2021
Downloadable Archival Material, English, 2022
SMHI, Samhällsplanering, 2022