Oxygen Survey in the Baltic Sea 2012 - Extent of Anoxia and Hypoxia, 1960 -2012

Type: Report
Series: RO 46
Author: Martin Hansson, Lars Andersson, Philip Axe, Jan Szaron


A climatology atlas of the oxygen situation in the deep water of the Baltic Sea was published in 2011 in the SMHI Report Oceanography No 42. The results for 2011 were preliminary and have in this report been updated as new additional data have been reported to ICES. The results for 2012 are preliminary and based on oxygen data collected during the annual Baltic International Acoustic Survey (BIAS) with contributions from Sweden, Poland, Estonia and Finland. Data from SMHI own cruises during the autumn have also been included. For the autumn period, August to October, each profile in the data set was examined for the occurrence of hypoxia (oxygen deficiency) and anoxia (total absence of oxygen). The depths of the onset of hypoxia and anoxia were then interpolated between sampling stations producing two surfaces representing the depth at which hypoxic and anoxic conditions are found. The volume and area of hypoxia and anoxia have been calculated and the results have then been transformed to maps and diagrams to visualize the annual autumn oxygen situation during the analysed period. The new results for 2011 and the preliminary results for 2012 show that the extreme oxygen conditions in the Baltic Proper after the regime shift in 1999 continues. Both the areal extent and the volume of hypoxia and anoxia are elevated to levels never seen before.