Extremes of Temperature, Oxygen and Blooms in the Baltic Sea in a Changing Climate

Abstract

In the future, the Baltic Sea ecosystem will be impacted both by climate change and by riverine and atmospheric nutrient inputs. Multi-model ensemble simulations comprising one IPCC scenario (A1B), two global climate models, two regional climate models, and three Baltic Sea ecosystem models were performed to elucidate the combined effect of climate change and changes in nutrient inputs. This study focuses on the occurrence of extreme events in the projected future climate. Results suggest that the number of days favoring cyanobacteria blooms could increase, anoxic events may become more frequent and last longer, and salinity may tend to decrease. Nutrient load reductions following the Baltic Sea Action Plan can reduce the deterioration of oxygen conditions.

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

“…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). Despite the high uncertainties involved, which are due to model shortcomings and unknown future scenarios of external nutrient loads, a basic conclusion seems to be that climate change can be expected to reinforce oxygen depletion, to increase phytoplankton biomass, and to reduce water transparency and biodiversity (due to decreased salinity) (e.g., Eilola et al 2012;Meier et al 2011bMeier et al , 2012Neumann et al 2012). Further, we found that in future climate, cod biomass may decrease and sprat biomass may increase assuming present day estimates of sustainable fishing (e.g., MacKenzie et al 2012;Niiranen et al 2012).…”

“…For dynamical downscaling, a high-resolution coupled atmosphere-ice-ocean-land surface model (the Rossby Centre Atmosphere Ocean model, RCAO), with lateral boundary data from global General Circulation Models (GCMs), was used to project the future climate of the Baltic Sea region (Meier et al 2011a. The regional scenario simulations differ depending on the applied GCM at the lateral boundaries and depending on the utilized Furthermore, three state-of-the-art coupled physicalbiogeochemical models were used to calculate changing concentrations of nitrate, ammonium, phosphate, autotrophs, zooplankton, detritus and oxygen, i.e., BALTSEM, ERGOM and RCO-SCOBI (Meier et al 2011bEilola et al 2012;Neumann et al 2012). Higher trophic levels were assessed with a food web model for the Baltic proper and statistical fish population models (MacKenzie 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).…”

Comparison of the AVI, modified SINTACS and GALDIT vulnerability methods under future climate-change scenarios for a shallow low-lying coastal aquifer in southern Finland

“…In future climate change scenarios, the salinity in the Baltic Sea region is predicted to decrease by about 2-50 % from the present level (Neumann et al 2012;Meier et al 2006), due to the predicted increase in freshwater inflow into the Baltic Sea. Millero and Kremling (1976) also reported that the salinity of water samples from the Baltic Sea appears to have remained stable during 30 years of water sampling.…”

Environmental Impacts—Marine Biogeochemistry

“…Blooms are expected to start earlier in summer, and N fixation might increase (Neumann 2010;Neumann et al 2012;Meier et al 2012). It was also shown that increasing nutrient loads due to climate-induced change in river run-off have a smaller impact on the modelled phytoplankton development than changes caused by socio-economic development.…”