Lehmann, Andreas, Hinrichsen, Hans-Harald, Getzlaff, Klaus and Myrberg, Kai (2014) Quantifying the heterogeneity of hypoxic and anoxic areas in the Baltic Sea by a simplified coupled hydrodynamic-oxygen consumption model approach. Journal of Marine Systems, 134 . pp. 20-28. DOI 10.1016/j.jmarsys.2014.02.012.

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Abstract

Highlights:
• Modeling of oxygen conditions of the Baltic Sea for the period 1970–2010 by a coupled hydrodynamic-oxygen consumption model
• Determination of the evolution of hypoxic and anoxic areas for the period 1970–2010 for the total Baltic Sea
• Determination of the frequencies of the occurrences of areas of oxygen deficiencies for the period 1970–2010
• Calculation of the Baltic Cod reproduction volumes in the Bornholm Basin for the period 1970–2010

Abstract:
The Baltic Sea deep waters suffer from extended areas of hypoxia and anoxia. Their intra- and inter-annual variability is mainly determined by saline inflows which transport oxygenated water to deeper layers. During the last decades, oxygen conditions in the Baltic Sea have generally worsened and thus, the extent of hypoxic as well as anoxic bottom water has increased considerably. Climate change may further increase hypoxia due to changes in the atmospheric forcing conditions resulting in less deep water renewal Baltic inflows, decreased oxygen solubility and increased respiration rates. Feedback from climate change can amplify effects from eutrophication. A decline in oxygen conditions has generally a negative impact on marine life in the Baltic Sea. Thus, a detailed description of the evolution of oxygenated, hypoxic and anoxic areas is particularly required when studying oxygen-related processes such as habitat utilization of spawning fish, survival rates of their eggs as well as settlement probability of juveniles. One of today's major challenges is still the modeling of deep water dissolved oxygen, especially for the Baltic Sea with its seasonal and quasi-permanent extended areas of oxygen deficiency. The detailed spatial and temporal evolution of the oxygen concentrations in the entire Baltic Sea have been simulated for the period 1970–2010 by utilizing a hydrodynamic Baltic Sea model coupled to a simple pelagic and benthic oxygen consumption model. Model results are in very good agreement with CTD/O2-profiles taken in different areas of the Baltic Sea. The model proved to be a useful tool to describe the detailed evolution of oxygenated, hypoxic and anoxic areas in the entire Baltic Sea. Model results are further applied to determine frequencies of the occurrence of areas of oxygen deficiency and cod reproduction volumes.

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