Second Assessment of Climate Change for the Baltic Sea Basin

Earth System Sciences; Atmospheric Sciences; Baltic Sea; Environmental Impacts; Regional Climate Change; Regional Climate Projection

Grasslands of Northern Europe and the Baltic States

This chapter deals with the grasslands of Northern Europe (Denmark, Faroe Islands, Finland, Iceland, Norway, Sweden) and the Baltic States (Estonia, Latvia, Lithuania), with a focus on natural and semi-natural grasslands of the lowlands, thus treating arctic-alpine and strongly intensified types only marginally. At present, grasslands cover ca. 7% of the study region, half of which are natural grasslands (mostly arctic-alpine, to a smaller extent also azonal and extra-zonal) and the other half secondary grasslands created by human land use (livestock grazing or haymaking). Both grassland categories have high importance for biodiversity in many taxa. However, particularly the secondary grasslands are profoundly negatively affected by area loss (conversion to other land uses) and quality loss (mainly due to intensification and to abandonment). Conservation measures typically try to mimic traditional low-intensity land uses that are agronomically not profitable anymore.Peer reviewe

The importance of benthic-pelagic coupling for marine ecosystem functioning in a changing world

Benthic-pelagic coupling is manifested as the exchange of energy, mass, or nutrients between benthic and pelagic habitats. It plays a prominent role in aquatic ecosystems, and it is crucial to functions from nutrient cycling to energy transfer in food webs. Coastal and estuarine ecosystem structure and function are strongly affected by anthropogenic pressures; however, there are large gaps in our understanding of the responses of inorganic nutrient and organic matter fluxes between benthic habitats and the water column. We illustrate the varied nature of physical and biological benthic-pelagic coupling processes and their potential sensitivity to three anthropogenic pressures - climate change, nutrient loading, and fishing - using the Baltic Sea as a case study and summarize current knowledge on the exchange of inorganic nutrients and organic material between habitats. Traditionally measured benthic-pelagic coupling processes (e.g., nutrient exchange and sedimentation of organic material) are to some extent quantifiable, but the magnitude and variability of biological processes are rarely assessed, preventing quantitative comparisons. Changing oxygen conditions will continue to have widespread effects on the processes that govern inorganic and organic matter exchange among habitats while climate change and nutrient load reductions may have large effects on organic matter sedimentation. Many biological processes (predation, bioturbation) are expected to be sensitive to anthropogenic drivers, but the outcomes for ecosystem function are largely unknown. We emphasize how improved empirical and experimental understanding of benthic-pelagic coupling processes and their variability are necessary to inform models that can quantify the feedbacks among processes and ecosystem responses to a changing world.Peer reviewe

Second Assessment of Climate Change for the Baltic Sea Basin

Earth System Sciences; Atmospheric Sciences; Baltic Sea; Environmental Impacts; Regional Climate Change; Regional Climate Projection

Sea Surface Temperature Climate Data Record for the North Sea and Baltic Sea

A 30-yr climate data record (CDR) of sea surface temperature (SST) has been produced with daily gap-free analysis fields for the North Sea and the Baltic Sea region from 1982 to 2012 by combining the Pathfinder AVHRR satellite data record with the Along-Track Scanning Radiometer (ATSR) Reprocessing for Climate (ARC) dataset and with in situ observations. A dynamical bias correction scheme adjusts the Pathfinder observations toward the ARC and in situ observations. Largest Pathfinder-ARC differences are found in the summer months, when the Pathfinder observations are up to 0.4 °C colder than the ARC observations on average. Validation against independent in situ observations shows a very stable performance of the data record, with a mean difference of -0.06 °C compared to moored buoys and a 0.46 °C standard deviation of the differences. The mean annual biases of the SST CDR are small for all years, with a negligible temporal trend when compared against drifting and moored buoys. Analysis of the SST CDR reveals that the monthly anomalies for the North Sea, the Danish straits, and the central Baltic Sea regions show a high degree of correlation for interannual and decadal time scales, whereas the monthly variability differs from one region to another. The linear trends of the 1982-2012 SST anomaly time series range from 0.037 °C yr-1 for the North Sea to 0.041 degrees C yr-1 for the Baltic Sea

Changing Salinity Gradients in the Baltic Sea As a Consequence of Altered Freshwater Budgets

Climate change is expected to enhance the hydrological cycle in northern latitudes reducing the salinity in the Baltic Sea, a land-locked marginal sea with a large catchment area located in northern Europe. With the help of ocean simulations forced by historical atmospheric and hydrological reconstructions and local observations, we analyzed long-term changes in the sea surface salinity of the Baltic Sea as well as its latitudinal gradient. The variability of both is dominated by multidecadal oscillations with a period of about 30 years, while both atmospheric variables, wind and river runoff, contribute to this variability. Centennial changes show a statistically significant positive trend in the North-South gradient of sea surface salinity for 1900–2008. This change is mainly attributed to increased river runoff from the northernmost catchment indicating a footprint of the anthropogenic impact on salinity with consequences for the marine ecosystem and species distributions