Entire Baltic Sea Research Articles

Estimating uncertainties of projected Baltic Sea salinity in the late 21st century

As the uncertainty of projected precipitation and wind changes in regional climate change scenario simulations over Europe for the late 21st century is large, we applied a multi‐model ensemble approach using 16 scenario simulations based upon seven regional models, five global models, and two emission scenarios to gain confidence in projected salinity changes in the Baltic Sea. In the dynamical downscaling approach a regional ocean circulation model and a large‐scale hydrological model for the entire Baltic Sea catchment area were used. Despite the uncertainties, mainly caused by global model biases, salinity changes in all projections are either negative or not statistically significant in terms of natural variability.

Data-driven analysis of joint coastal extremes near a large non-tidal estuary in North Europe

The Vistula river estuary, located in the Gulf of Gdańsk, is the largest river mouth in the entire Baltic Sea catchment area. Thus, the assessment of the likelihood of flood events for this region has become a pressing issue. Such analyses should include the worst scenario of joint coastal extremes due to simultaneous high levels of water in the river and sea. The simultaneously recorded daily water levels in the river and sea in the 1961–1989 period have made it possible to employ data-intensive signal processing techniques to address this problem by: (1) identification of the physical background of patterns embedded in both series with the Singular Spectrum Analysis (SSA) and (2) assessment of the degree of coupling between pairs of patterns from both series that are deemed most likely to trigger a joint extreme; this is done with the Canonical Correlation Analysis (CCA). For the Vistula estuary it was found that although the annual cycles encompass the largest portions of variances of both signals, they cannot be held responsible for joint extremes due to a considerable phase shift between them. However, both signals are often disturbed by random deviations from this basic behavior and these deviations emerged as separate patterns. Their magnitudes are to some extent correlated with the growth of water level in the sea and river and therefore they could be assumed to act as a pair of potential drivers of joint extremes. The degree of their coupling was found to be generally low with maximums in November, February and/or March, which indicates the low likelihood of a great flood event due to the combined effect of high sea and river water level. The results are also believed to be at least partly representative of other estuaries in North Europe, where annual cycles in seawater and water in (large) rivers are similar, e.g. Scheldt, Rijn, Elbe.

Distribution Patterns of Isomorphic Cold-Water Dinoflagellates (Scrippsiella/Woloszynskia Complex) Causing ‘red tides’ in the Baltic Sea

During the latest years medium-sized (15–30 μm), single-celled dinoflagellates have been reported to form blooms in the northern Baltic Proper and the Gulf of Finland in winter and spring. Recent studies (Kremp et al., 2003. Proceedings of the 7th International conference of Modern and Fossil Dinoflagellates, September 21–25, Nagasaki, Japan, 66 pp.) indicate that those blooms are caused by two isomorphic species – Scrippsiella hangoei (Schiller) Larsen, and a new species, tentatively belonging to the genus Woloszynskia. Until now there has been no report on how widely distributed these phytoplankton species are in the Baltic Sea. In this study, the occurrence of Scrippsiella/Woloszynskia complex in the entire Baltic Sea was investigated, by using monitoring data from 1997 to 2003. The species occurred in a salinity range from 2 to 8 PSU. Highest concentrations were observed at salinity 4.5–6.5 PSU. Maximum cell densities of Scrippsiella/Woloszynskia complex in the water column were mainly obtained in April or in the beginning of May by the water temperature 6 °C. Bloom formations in the Baltic Proper and in the Gulf of Finland may not only be explained by optimum temperature and salinity, but also with other factors e.g. high nutrient concentrations and good seeding conditions from the sediments.

Atmospheric response to different sea surface temperatures in the Baltic Sea: coupled versus uncoupled regional climate model experiments

A climate change experiment with a fully coupled high resolution regional atmosphere–ocean model for the Baltic Sea is compared to an experiment with a stand-alone regional atmospheric model. Both experiments simulate 30-yr periods with boundary data from the same global climate model system. This particular global model system simulates very high sea surface temperatures during summer for the Baltic Sea at the end of this century under the investigated emission scenario. We show that the sea surface temperatures are less warm in the coupled regional model compared to the global model system and that this difference is dependent on the atmospheric circulation. In summers with a high NAO index and thereby relatively strong westerly flow over the North Atlantic the differences between the two models are small, while in summers with a weaker, more northerly flow over the Baltic Sea the differences are very large. The higher sea surface temperatures in the uncoupled experiment lead to an intensified hydrological cycle over the Baltic Sea, with more than 30% additional precipitation in summer taken as an average over the full 30-yr period and over the entire Baltic Sea. The differences are mostly local, over the sea, but there are differences in surrounding land areas.

The Southern Baltic Sea and its coast in transition

This special feature is based on results of an interdisciplinary priority program of the German Federal Environmental Foundation (Deutsche Bundesstiftung Umwelt, DBU) called “die sudliche Ostsee und ihre Kuste im Wandel” (the Southern Baltic Sean and its coast in transition). The Baltic Sea is the world’s largest brackish-water body (area 415.00 km 2 , volume ca. 22.000 km 3 ). The long coast-line (20.000 km) is shared by 9 nations, with 70 millions inhabitants in the coastal zone and 100 millions inhabitants in the hydrological catchment region. As a geologically young and relatively shallow sea-basin, the Baltic Sea is an area of rapid environmental change. It is characterised by pronounced environmental gradients and a pronounced importance of the sea-land interface for the functioning of the entire Baltic Sea system. The density of human settlement, particularly along the southern coast, and the almost enclosed basin of the Baltic Sea make it particularly sensitive to anthropogenic impact and changes in human utilisation of the sea, its coast and its catchment. In addition to the usual, more gradual changes of human impact along the northern Baltic coast, the southern Baltic coast and its catchment have witnessed the collapse of the socialist economic system with its associated rapid economic transitions. Our main study region, the coast of Mecklenburg-Vorpommern (the coastal state in eastern Germany) may serve as a paradigmatic example with its transition from an economy dominated by industry and agriculture to an economy dominated by tourism. Understanding the ecosystem consequences of such changes, predicting future trends and developing strategies for sustainable use requires research across a wide range of time-scales, from the geological scale (coastal

A simulation of the Gulf of Finland ecosystem with a 3D model

Abstract. Comparison of simulations with a 3D eutrophication model with observation data for the Gulf of Finland showed that the model reproduced satisfactorily typical features of seasonal variability in the Gulf of Finland system, especially in the surface layers. However, as the model is driven by real atmospheric forcing for 1995–2000 and by climatically average river runoff and nutrient loads, it was unable to simulate the exact succession of events occurring in the deep layers of the gulf during this period. More time-specific data are needed both for prescription of boundary conditions and as validation criteria in order to further calibrate the model and test its performance. Key words: eutrophication, 3D modelling, hydrodynamics, biogeochemical cycles, validation, Baltic Sea, Gulf of Finland. INTRODUCTION The Gulf of Finland collects from its watershed about 20% of the terrestrial inputs of total nitrogen and phosphorus into the entire Baltic Sea (HELCOM, 1998). The eastern part of the gulf, which receives over 70% and 80% of the total phosphorus and nitrogen land loads to the gulf, respectively (Pitkanen et al., 2001), is even more subject to anthropogenic impact. The elevated trophic status of the gulf results in occasional cyanobacteria blooms, oxygen deficiency, macrofauna

Developments in Operational Shelf Sea Modelling in Danish Waters

An initial implementation of an operational system for the Danish waters has been carried out. The system consists of an observational network of water level stations, a two-dimensional model that computes simultaneously areas with different grid resolution, and a sequential data assimilation method. For assimilation of water level measurements an approximate Kalman filter algorithm, the ensemble Kalman filter, has been implemented. The ensemble Kalman filter has a computational cost much lower than the cost associated with a full Kalman filter application, and therefore it is suitable to be applied in an operational system. The error covariance matrix in this specific case tends to a quasi-steady state after a few days of assimilation. Thus, a Kalman filter with a constant weighting matrix has been applied during a 13-day test period to assimilate observed water levels in a model covering the entire North Sea and Baltic Sea area. The corrections achieved by the assimilation procedure are significant in most of the validation stations. Moreover, the error estimation provided by the filter is very accurate, especially in the inner Danish waters.

Seasonal variations in phosphorus species in the surface sediments of the Gulf of Riga, Baltic Sea

The redox-dependent variations in concentrations of phosphorus at two different accumulation bottom areas were investigated in the Gulf of Riga (Baltic Sea) between December 1993 and January 1995. The sediment samples from nine sampling occasions were analyzed for phosphorus forms and redox potential. The average concentrations of total phosphorus measured in 0–1 cm (65 and 89 μmol P g −1 for sites G5 and T3, respectively) were among the highest reported from the entire Baltic Sea. Redox-dependent “mobile” phosphorus (MP) contributed more than 50% of total in the uppermost-oxidized centimeter, whereas in reduced layers it was 16–18% throughout the year. The significant differences (ANOVA, P<0.01) among months of inorganic phosphorus (IP) concentration at 0–1 cm were observed at site G5 due to temporary accumulation of mobile phosphorus mediated by redox-dependent bacteria activity during summer. On the contrary no accumulation was observed at T3 probably as a result of low redox potential caused by high accumulation rates and low bioturbation. Although the water column above sediments remained oxic throughout the investigation period, the redox potential at site T3 was close to the redoxcline (i.e., +230 mV) during summer. Further increase of eutrophication might lead to development of anoxic conditions at sediment–water interface and that in turn will result in rapid release of redox-dependent phosphorus stored in surface sediments. The availability of excess phosphorus will further enhance eutrophication in partly phosphorus-limited Gulf of Riga.

Giving Advice on Cost Effective Measures for a Cleaner Baltic Sea: A Challenge for Science

The Baltic Sea is one of the world's seas that is most severely affected by human activities. Although there is an international agreement that nutrient input to the Baltic should be reduced, the measures taken so far have not resulted in major reductions in nutrient inputs nor in environmental improvements. The reasons for this are partly due to lack of knowledge on large-scale relationships and couplings between physics, biogeochemistry and ecological properties. But there is also a lack of overall drainage basin-wide analyses on cost-effective measures. There is a danger in making the wrong decisions, e.g. implement reduction schemes that are at worst ineffective or at best, far from cost effective. Researchers from many disciplines are faced with a common challenge: To develop a decision-support system, which can be used as the scientific base for cost-effective measures for the entire Baltic Sea. Such an effort is now being made within the research program MARE (http://www.mare.su.se).

Changes in the C, N, P burial rates in some Baltic Sea sediments over the last 150 years—relevance to P regeneration rates and the phosphorus cycle

Three major depositional basins (the Gdansk, Bornholm and Eastern Gotland basins) of the Baltic Proper, which together account for .50% of the depositional areas in the entire Baltic Sea, have accumulated increased amounts of sediment and organic carbon during the last 50 years, as is shown in 210 Pb-dated sediment cores. The shallow Arkona Basin has had constant accumulation rates and rate increases of bulk sediment, organic carbon and aluminium in the Bornholm Basin are parallel and are interpreted to reflect increased material input from land or from erosion of shallow-water areas. In the Gdansk and Eastern Gotland basins, the accumulation rates of mineral matter have risen at lower rates than those of organic carbon and point to preferential enrichment of organic matter. At increasing rates of burial, the material in the Gdansk and Eastern Gotland basins appears to have been depleted in phosphorus relative to nitrogen and organic carbon. Using C:N:P ratios from a sediment trap mooring in the Gotland Basin and from fluffy layer material in the Pomeranian Bight as characteristic ratios for sedimenting material, we find evidence for significant increases in the ratios of C to P in sediments younger than 15‐25 years in cores from the Eastern Gotland basin, coincident with H2S build-up in deep waters. Paired oxygen and phosphorus concentration data from the sub-halocline water column of the Gotland Basin covering the time since 1970 suggest that the phosphate reflux is fed from two sources: At the transition from oxic to anoxic conditions, iron-bound phosphate is suddenly liberated at the sediment‐water interface and results in a concentration jump of approximately 2 mmol dm 23 phosphate in deep water. During anoxic periods with H2S in bottom waters, phosphate diffuses out of the sediment and adds to the dissolved phosphate pool. Our data imply that the sediment contributed approximately 14,000 t a 21 of phosphorus to the water column of the deep Gotland Basin since the early 1970s. Compared to total P input to the Baltic Sea (1993: 39,000 t), the reflux of P from anoxic sediments in the Gotland Basin thus is a major source of P for the Baltic Sea. On time scales of years and decades, the reflux of phosphorus from the sediments may be the reason for discrepancies between the ratios of nitrogen and phosphorus in the Baltic Sea and for a lack of effects of declining phosphate discharge into this large ecosystem. q 2000 Elsevier Science B.V. All rights reserved.

Gauge-Radar network adjustment for the baltic sea experiment

The gauge adjustment technique used to produce 2 × 2 km 3- and 12-hour radar-based accumulated precipitation datasets for the Baltic Sea Experiment is presented. The gauge adjustment technique is based on the gauge-to-radar ratio. A distance-dependent adjustment factor is derived and it is weighted against a spatially analyzed adjustment factor according to the local observation density and estimated spatial decorrelation distance. A preliminary adjustment strategy is applied in order to normalize data from many radars to a common level and to minimize the bias with gauges. The final adjustment field applied to radar accumulations is shown, through validation against independent gauge data, to minimize the bias between radar and gauge sums while raising the explained variance, compared to unadjusted radar sums. Areas not covered by radar are subjected to an optimal interpolation of systematically corrected gauge sums, and this field is merged with the gauge adjusted radar field in order to cover the entire Baltic Sea Experiment region.

ESTIMATION OF RIVERINE LOADS OF NITROGEN AND PHOSPHORUS TO THE BALTIC SEA, 1970-1993

This article presents the results of the first critical examination of time series of riverine nutrient-load data for the entire Baltic Sea drainage area. Water quality data collected by or for the different national environmental agencies were compiled and analysed statistically to identify and remove inconsistent or obviously incorrect observations. Moreover, sampling tours were undertaken to acquire additional information about the present nutrient concentrations in the largest rivers in the study area. Gaps in the time series of approved data were then filled in by employing statistical interpolation and extrapolation methods. Thereafter, the concentration and runoff data were combined to obtain estimates of monthly nutrient loads for the time period 1970–93. The results of the calculations showed that although there had been substantial changes in land use, atmospheric deposition and wastewater treatment in many parts of the study area, the total riverine loads of nitrogen (N) and phosphorus (P) to the Baltic Sea have been fairly constant since 1980, and most likely also since 1970. Moreover, the interannual variation was clearly correlated to the runoff. The mean annual loads for the time period 1980–93 were found to be about 825 000 tonnes N and 41 000 tonnes P, respectively. This implies that (i) several other investigators have strongly underestimated the riverine loads of nutrients, especially the nitrogen, and that (ii) the riverine loads by far exceed the input to the Baltic Sea from other sources, {i.e.} atmospheric deposition, direct emissions from cities and industries along the Baltic Sea coast and nitrogen fixation by marine algae.

The ice winter of 1997/98 on the german coasts between ems and oder, with a survey of the entire baltic sea

The ice winter of 1997/98 on the german coasts between ems and oder, with a survey of the entire baltic sea

The Regional Geology and Hydrocarbon Potential of the Baltic Sea

The Baltic Sea is roughly equivalent in size to the North Sea. Like the North Sea, is has an excellent oil prone source rock present over most of the area. In the entire Baltic Sea about 40 wells have been drilled. During the 1980s, exploration was carried out in the Soviet, Polish, and East German sectors of the Baltic Sea by Petrobaltic. Twenty-eight wells were drilled, 14 of which tested hydrocarbons. Two wells have been drilled in Danish waters and 11 in Swedish waters - all dry holes. Most of the Baltic Sea is included in the Baltic syneclise. In the deepest part of the basin a full Paleozoic and Mesozoic section is present. Major structural features are associated with reactivation of old basement faults. Most hydrocarbon discoveries are associated with structural arches. Exploration targets are Cambrian sandstones and Ordovician and Silurian reefs. The major discoveries are the B3 field in Poland and the D6 field offshore Lithuania and Kaliningrad, both of which have in-place reserves of around 100 million bbl. The Teisseyre-Tornquist line to the southwest represents the plate boundary between the East European platform and Europe. Repeated strike slip movements along this zone result in a complex patternmore » of extensional and compressional features in the Danish and German sectors. Primary exploration targets include Permian carbonates and sandstones as well as older zones. Gas has been tested in the German sector onshore.« less

Long-term, seasonal and spatial variations of nitrogen, phosphorus and silicate in the Baltic: An overview

A census for standing stocks of nitrate, ammonia, phosphate, total nitrogen, phosphorus and silicate in the Baltic Sea is given for two 5-year periods (1972–1976 and 1977–1981). It is based on monthly means calculated fromall observations in the ICES databank resolved into a one-degree longitude-latitude grid for 22 depth intervals. The spatial and temporal variations in monthly surface concentrations are described. Features such as the nitrogen limitation of the Baltic versus the phosphorus limitation of the Bothnian Bay are readily found. The total amount of nutrients in the different subareas of the Baltic are calculated, based on a corresponding volume database. The amounts of inorganic and total nitrogen have increased in the latter period, while silicate has decreased during the same period. Though both phosphate and total phosphorus have increased during some seasons in some basins, the total amounts in the entire Baltic Sea have not changed significantly. Although the inputs are, to a large extent, counteracted by internal sinks, the system is far from a steady state. Increasing winter concentrations of nitrogen and phosphorus and the depletion of silicate, indicate an increase of primary production.