Catálogo de publicaciones - libros

This chapter builds on the comprehensive summary of climate change scenarios in the first BACC assessment published in 2008. This chapter first addresses the dynamical downscaling of general circulation model (GCM) results to the regional scale, focussing on results from 13 regional climate model (RCM) simulations in the ENSEMBLES project as this European-scale ensemble simulation is also relevant for the Baltic Sea region and many studies on temperature, precipitation, wind speed and snow amounts have been performed. This chapter then reviews statistical downscaling studies that use large-scale atmospheric variables (predictors) to estimate possible future change in several smaller scale fields (predictands), with the greatest emphasis given to hydrological variables (such as precipitation and run-off). For the Baltic Sea basin, the findings of the statistical downscaling studies are generally in line with studies employing dynamical downscaling.

This chapter reviews studies on projected hydrological changes within the Baltic Sea catchment area published since the first assessment of climate change in the Baltic Sea region in 2008. Hydrological impact studies have been carried out in almost all countries in the area. The large differences in hydrological conditions (present and projected) from northern Scandinavia to the southern Baltic Sea area are addressed. The chapter considers the impacts of snow accumulation and melt, river discharge and flooding. Water resources with studies on dry periods and groundwater resources are also covered. In contrast to the first assessment, uncertainty has received significant attention. In contrast to traditional hydrological studies, projections of climate impacts on hydrology are associated with uncertainties related to the models and greenhouse gas (GHG) emission scenarios used. In several studies, individual uncertainty sources are quantified and compared.

This chapter assesses recent results of changes in water temperature, salinity, sea ice, storm surges and wind waves during the twenty-first century in scenario simulations for the Baltic Sea. There have been several improvements since the first Baltic Sea assessment of climate change: the number of relevant scenario simulations has increased, ensembles of transient simulations with improved models based upon the scenarios and global models of IPCC’s Fourth Assessment Report (AR4) have been analysed, and changes in biogeochemical cycles are now considered. The scenario simulations project that water temperatures will increase in the future, with the greatest changes in the northern Baltic Sea during summer. In agreement with earlier studies, sea-ice cover is projected to decrease drastically. Salinity is projected to decrease due to increased river run-off, whereas the impact of wind changes on salinity is negligible because the latter is relatively small. However, uncertainty in salinity projections is large owing to considerable bias in the simulated water balance. According to one study, salt transport into the Baltic Sea is unchanged. Sea-level rise has greater potential to increase surge levels in the Baltic Sea than increased wind speed, and changes in wind waves are projected to be small.

Global warming is causing sea levels to rise, primarily due to loss of land-based ice masses and thermal (steric) expansion of the world oceans. Sea level does not rise in a globally uniform manner, but varies in complex spatial patterns. This chapter reviews projections of the individual contributions to sea-level rise. These are used to assemble a mid-range scenario of a 0.70 ± 0.30-m sea-level rise over the twenty-first century (based on the SRES A1B scenario) and a high-end scenario of 1.10 m. The sea-level projection was regionalised to the Baltic Sea area by taking into account local dynamic sea-level rise and weighting the components of the sea-level budget by their static equilibrium fingerprint. This yields a mid-range Baltic Sea sea-level rise that is ~80 % of the global mean. Ongoing glacial isostatic adjustment (GIA) partly compensates for local sea-level rise in much of the region. For the mid-range scenario, this equates to a twenty-first century relative sea-level rise of 0.60 m near Hamburg and a relative sea-level fall of 0.35 m in the Bothnian Bay. The high-end scenario is characterised by an additional 0.5 m.

This chapter addresses sources and trends of atmospheric pollutants and deposition in relation to the Baltic Sea region. Air pollution is shown to have important effects, including significant contributions to nitrogen loading of the Baltic Sea area, ecosystem impacts due to acidifying and eutrophying pollutants and ozone, and human health impacts. Compounds such as sulphate and ozone also have climate impacts. Emission changes have been very significant over the past 100 years, although very different for land- and sea-based sources. Land-based emissions generally peaked around 1980–1990 and have since reduced due to emissions control measures. Emissions from shipping have been steadily increasing for decades, but recent measures have reduced sulphur and particulate emissions. Future developments depend strongly on policy developments. Changes in concentration and deposition of the acidifying components generally follow emission changes within the European area. Mean ozone levels roughly doubled during the twentieth century across the northern hemisphere, but peak levels have reduced in many regions in the past 20 years. The main changes in air pollution in the Baltic Sea region are due to changes in emissions rather than to climate change.

This chapter describes observed historical and projected future impacts of climate change on the coastal and terrestrial ecosystems of the Baltic Sea basin. Because terrestrial and aquatic ecosystems interact, this chapter gives particular emphasis to the coastal zone as a contact area for terrestrial, marine and atmospheric processes. Archipelagos and post-glacial land uplift are particular features of the Baltic Sea basin and so receive special consideration. This chapter comprises three main sections. The first describes coastal zone and archipelago ecosystems in the Baltic Sea region and evaluates the potential impacts of climate change. The second examines a case study for the effect of current and future climate change on coastal bird populations and communities. The third evaluates the effects of current and future climate change on forests and natural plant communities in the Baltic Sea basin and the ways in which terrestrial ecosystems may interact with aquatic ecosystems. Climate-related changes in carbon storage are also discussed.

Climate change effects on freshwater biogeochemistry and riverine loads of biogenic elements to the Baltic Sea are not straight forward and are difficult to distinguish from other human drivers such as atmospheric deposition, forest and wetland management, eutrophication and hydrological alterations. Eutrophication is by far the most well-known factor affecting the biogeochemistry of the receiving waters in the various sub-basins of the Baltic Sea. However, the present literature review reveals that climate change is a compounding factor for all major drivers of freshwater biogeochemistry discussed here, although evidence is still often based on short-term and/or small-scale studies.

Marine biogeochemistry deals with the budgets and transformations of biogeochemically reactive elements such as carbon, nitrogen and phosphorus. Inorganic nitrogen and phosphorus compounds are the major nutrients and control organic matter (biomass) production in the surface water. Due to various anthropogenic activities, the input of these nutrients into the Baltic Sea has increased drastically during the last century and has enhanced the net organic matter production by a factor of 2–4 (eutrophication). This has led to detrimental oxygen depletion and hydrogen sulphide production in the deep basins of the Baltic Sea. Model simulations based on the Baltic Sea Action Plan (BSAP) indicate that current eutrophication and thus extension of oxygen-depleted areas cannot be reversed within the next hundred years by the proposed nutrient reduction measures. Another environmental problem is related to decreasing pH (acidification) that is caused by dissolution of the rising atmospheric CO. Estimates indicate a decrease in pH by about 0.15 during the last 1–2 centuries, and continuation of this trend may have serious ecological consequences. However, the concurrent increase in the alkalinity of the Baltic Sea may have significantly counteracted acidification.

Increase in sea surface temperature is projected to change seasonal succession and induce dominance shifts in phytoplankton in spring and promote the growth of cyanobacteria in summer. In general, climate change is projected to worsen oxygen conditions and eutrophication in the Baltic Proper and the Gulf of Finland. In the Gulf of Bothnia, the increasing freshwater discharge may increase the amount of dissolved organic carbon (DOC) in the water and hence reduce phytoplankton productivity. In winter, reduced duration and spatial extent of sea ice will cause habitat loss for ice-dwelling organisms and probably induce changes in nutrient dynamics within and under the sea ice. The projected salinity decline will probably affect the functional diversity of the benthic communities and induce geographical shifts in the distribution limits of key species such as bladder wrack and blue mussel. In the pelagic ecosystem, the decrease in salinity together with poor oxygen conditions in the deep basins will negatively influence the main Baltic Sea piscivore, cod. This has been suggested to cause cascading effects on clupeids and zooplankton.

Climate change is having an undeniable influence on coastal areas. This chapter describes the growing threat of climate change on the Baltic Sea coastline, with an emphasis on field research focused on storm surges and coastal retreat. The main climatic factors driving change in the Baltic Sea coastal zone are wind, waves, storm surges, ice jams and flooding. The cumulative effects of these drivers are also important. For example, a costly coastal protection scheme in one area may result in coastal erosion in another. Natural and man-made coastal features are experiencing unprecedented change; important natural habitats, coastal settlements and local economies are all being affected. The extent of storm surge impacts depends on the exposure of a shoreline to a surge event. The submergent and soft coastal relief of the southern Baltic Sea area is under most threat; the rate of retreat depending on the frequency and strength of the storm surges. The rate of coastal retreat has also increased in recent years due to sea-level rise and loss of beaches.