Climate Dynamics

, Volume 53, Issue 1–2, pp 1145–1166 | Cite as

Disentangling the impact of nutrient load and climate changes on Baltic Sea hypoxia and eutrophication since 1850

  • H. E. M. MeierEmail author
  • K. Eilola
  • E. Almroth-Rosell
  • S. Schimanke
  • M. Kniebusch
  • A. Höglund
  • P. Pemberton
  • Y. Liu
  • G. Väli
  • S. Saraiva


In the Baltic Sea hypoxia has been increased considerably since the first oxygen measurements became available in 1898. In 2016 the annual maximum extent of hypoxia covered an area of the sea bottom of about 70,000 km2, comparable with the size of Ireland, whereas 150 years ago hypoxia was presumably not existent or at least very small. The general view is that the increase in hypoxia was caused by eutrophication due to anthropogenic riverborne nutrient loads. However, the role of changing climate, e.g. warming, is less clear. In this study, different causes of expanding hypoxia were investigated. A reconstruction of the changing Baltic Sea ecosystem during the period 1850–2008 was performed using a coupled physical-biogeochemical ocean circulation model. To disentangle the  drivers of eutrophication and hypoxia a series of sensitivity experiments was carried out. We found that the decadal to centennial changes in eutrophication and hypoxia were mainly caused by changing riverborne nutrient loads and atmospheric deposition. The impacts of other drivers like observed warming and eustatic sea level rise were comparatively smaller but still important depending on the selected ecosystem indicator. Further, (1) fictively combined changes in air temperature, cloudiness and mixed layer depth chosen from 1904, (2) exaggerated increases in nutrient concentrations in the North Sea and (3) high-end scenarios of future sea level rise may have an important impact. However, during the past 150 years hypoxia would not have been developed if nutrient conditions had remained at pristine levels.


Coastal seas Numerical modeling Reconstruction Eutrophication Climate change Hypoxia Cyanobacteria 



The research presented in this study is part of the Baltic Earth program (Earth System Science for the Baltic Sea region, see and was funded by the Swedish Research Council (VR) within the project “Reconstruction and projecting Baltic Sea climate variability 1850–2100” (Grant No. 2012–2117) and by the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) within the project “Cyanobacteria life cycles and nitrogen fixation in historical reconstructions and future climate scenarios (1850–2100) of the Baltic Sea” (Grant No. 214-2013-1449). Observations from the long-term, environmental monitoring programs at IOW, SMHI and FMI were used. Dr. Bo G. Gustafsson is acknowledged for providing compiled observations from the Baltic Environmental Database (BED) including measurements from the IOW and SMHI environmental monitoring programs. Special thanks also to Dr. Oleg Savchuk who supported us with the latest update of nutrient pools from BED. We thank two anonymous reviewers for their positive comments.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Physical Oceanography and InstrumentationLeibniz Institute for Baltic Sea Research WarnemündeRostockGermany
  2. 2.Department of Research and DevelopmentSwedish Meteorological and Hydrological InstituteNorrköpingSweden
  3. 3.Climate Information and StatisticsSwedish Meteorological and Hydrological InstituteNorrköpingSweden
  4. 4.Department of Marine SystemsTallinn University of TechnologyTallinnEstonia
  5. 5.Department of Mechanical EngineeringTechnical University of LisbonLisbonPortugal

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