Reconstructing the Development of Baltic Sea Eutrophication 1850–2006

Abstract

A comprehensive reconstruction of the Baltic Sea state from 1850 to 2006 is presented: driving forces are reconstructed and the evolution of the hydrography and biogeochemical cycles is simulated using the model BALTSEM. Driven by high resolution atmospheric forcing fields (HiResAFF), BALTSEM reproduces dynamics of salinity, temperature, and maximum ice extent. Nutrient loads have been increasing with a noteworthy acceleration from the 1950s until peak values around 1980 followed by a decrease continuing up to present. BALTSEM shows a delayed response to the massive load increase with most eutrophic conditions occurring only at the end of the simulation. This is accompanied by an intensification of the pelagic cycling driven by a shift from spring to summer primary production. The simulation indicates that no improvement in water quality of the Baltic Sea compared to its present state can be expected from the decrease in nutrient loads in recent decades.

ECOSUPPORT: A Pilot Study on Decision Support for Baltic Sea Environmental Management

“…The Baltic Sea models applied in ECOSUPPORT are capable of simulating past climate variations and eutrophication since 1850, building confidence that the models are able to simulate future changes (e.g., Eilola et al 2011;Gustafsson et al 2012;Niiranen et al 2012;Ruoho-Airola et al 2012). In future climate, water temperatures are projected to increase and salinities are projected to decrease (due to the increased total freshwater supply), which is in accordance with earlier studies (e.g., Arheimer et al 2012;Meier et al 2012;Neumann et al 2012).…”

“…The ECOSUPPORT work plan was built on the confidence of models' capacity to simulate the changing climate, and included the following aspects: (i) the assessment of predictive skills of the models by comparing observed and simulated past climate variability (i.e., quantification of model uncertainties) and analyzing causes of observed variations (e.g., Gustafsson et al 2012;Meier et al 2012;Niiranen et al 2012), (ii) the performance of multi-model ensemble simulations of the marine ecosystem for 1850-2100, forced by reconstructions of the past climate (e.g., Gustafsson et al 2012;Ruoho-Airola et al 2012) and various future greenhouse gas emission scenarios and airand river-borne nutrient load scenarios (ranging from a pessimistic business-as-usual to the most optimistic case) (e.g., Arheimer et al 2012;Eilola et al 2012;MacKenzie et al 2012;Meier et al 2012;Neumann et al 2012), (iii) the analysis of projections for the future Baltic Sea ecosystem, using a probabilistic approach accounting for uncertainties caused by biases of regional and global climate models, lack of process description in state-of-the-art ecosystem models, unknown greenhouse gas emissions and nutrient loadings as well as natural variability (e.g., Arheimer et al 2012;MacKenzie et al 2012;Meier et al 2012;Neumann et al 2012;Niiranen et al 2012), (iv) the assessment of climate change impacts on the marine biota, like effects of ocean acidification (e.g., Havenhand 2012), biodiversity and fish populations with focus on cod, sprat and herring (e.g., MacKenzie et al 2012;Niiranen et al 2012), (v) a socioeconomic impact assessment (e.g., Piwowarczyk et al 2012), (vi) the generation of a freeaccess data base of scenario model results and tools to access the database with the help of a decision support system (DSS) 2 and finally (vii) the dissemination of project results to stakeholders, decision makers and the public (see below).…”

Impact of Climate Change on Ecological Quality Indicators and Biogeochemical Fluxes in the Baltic Sea: A Multi-Model Ensemble Study

“…About 85 million people live in the Baltic catchment area which is four times larger than the Baltic Sea surface area (e.g., Leppäranta and Myrberg 2009). During the past 100 years, parts of the Baltic Sea have changed from oligotrophic to eutrophic systems, caused by human-induced nutrient load increases (Elmgren 2001;Savchuk et al 2008;Gustafsson et al 2012). As a consequence of eutrophication, environmental problems like spreading of hypoxia and increased frequency and intensity of cyanobacteria blooms have been observed (Vahtera et al 2007).…”

Recent Change—Marine Circulation and Stratification

“…They used data from daily monitoring at a few long-term stations, such as Christiansø, located close to the island of Bornholm, as well as data from irregular open water sampling, and applied advanced data homogeneity and spatial synchrony matching procedures to ensure sufficient data quality for climate analysis (MacKenzie and Schiedek 2007b). Their results showed little evidence of a gradual linear increase or decrease in SST since the mid-late 1800s, however; in contrast, modelling results by Gustafsson et al (2012) suggest a rise in SST temperature of 0.8°C over the past 150 years. There have been earlier warm periods in the mid-late 1800s and in the mid-1900s, especially in the 1930s.…”