ISSN 1239-6095 (print),   ISSN 1797-2469 (online)
© Boreal Environment Research 2009

Contents of Volume 14 Number 1

5th Study Conference on BALTEX — selected papers

Preface. Boreal Env. Res. 14: 1.
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Carlsson, B., Rutgersson, A. & Smedman, A.-S. 2009: Investigating the effect of a wave-dependent momentum flux in a process oriented ocean model. Boreal Env. Res. 14: 3–17.
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Gustafsson, E. O. & Omstedt, A. 2009: Sensitivity of Baltic Sea deep water salinity and oxygen concentration to variations in physical forcing. Boreal Env. Res. 14: 18–30.
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Jaagus, J. 2009: Regionalisation of the precipitation pattern in the Baltic Sea drainage basin and its dependence on large-scale atmospheric circulation. Boreal Env. Res. 14: 31–44.
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Jakobson, E., Ohvril, H. & Elgered, G. 2009: Diurnal variability of precipitable water in the Baltic region, impact on transmittance of the direct solar radiation. Boreal Env. Res. 14: 45–55.
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Lind, P. & Kjellström, E. 2009: Water budget in the Baltic Sea drainage basin: Evaluation of simulated fluxes in a regional climate model. Boreal Env. Res. 14: 56–67.
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Tedesco, L., Vichi, M., Haapala, J. & Stipa, T. 2009: An enhanced sea-ice thermodynamic model applied to the Baltic Sea. Boreal Env. Res. 14: 68–80.
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Bhend, J. & von Storch, H. 2009: Is greenhouse gas forcing a plausible explanation for the observed warming in the Baltic Sea catchment area? Boreal Env. Res. 14: 81–88.
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Draveniece, A. 2009: Detecting changes in winter seasons in Latvia: the role of arctic air masses. Boreal Env. Res. 14: 89–99.
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Jacob, D. & Lorenz, P. 2009: Future trends and variability of the hydrological cycle in different IPCC SRES emission scenarios — a case study for the Baltic Sea region. Boreal Env. Res. 14: 100–113.
Abstract
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Kjellström, E. & Lind, P. 2009: Changes in the water budget in the Baltic Sea drainage basin in future warmer climates as simulated by the regional climate model RCA3. Boreal Env. Res. 14: 114–124.
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Madsen, K. S. & Højerslev, N. K. 2009: Long-term temperature and salinity records from the Baltic Sea transition zone. Boreal Env. Res. 14: 125–131.
Abstract
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Saue, T. & Kadaja, J. 2009: Simulated crop yield — an indicator of climate variability. Boreal Env. Res. 14: 132–142.
Abstract
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Sepp, M. 2009: Changes in frequency of Baltic Sea cyclones and their relationships with NAO and climate in Estonia. Boreal Env. Res. 14: 143–151.
Abstract
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Soomere, T., Leppäranta, M. & Myrberg, K. 2009: Highlights of the physical oceanography of the Gulf of Finland reflecting potential climate changes. Boreal Env. Res. 14: 152–165.
Abstract
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Venäläinen, A., Jylhä, K., Kilpeläinen, T., Saku, S., Tuomenvirta, H., Vajda, A. & Ruosteenoja, K. 2009: Recurrence of heavy precipitation, dry spells and deep snow cover in Finland based on observations. Boreal Env. Res. 14: 166–172.
Abstract
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Graham, L. P., Olsson, J., Kjellström, E., Rosberg, J., Hellström, S.-S. & Berndtsson, R. 2009: Simulating river flow to the Baltic Sea from climate simulations over the past millennium. Boreal Env. Res. 14: 173–182.
Abstract
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Kowalewska-Kalkowska, H. & Wisniewski, B. 2009: Storm surges in the Odra mouth area during the 1997–2006 decade. Boreal Env. Res. 14: 183–192.
Abstract
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Kundzewicz, Z. W. 2009: Adaptation to floods and droughts in the Baltic Sea basin under climate change. Boreal Env. Res. 14: 193–203.
Abstract
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Gryning, S. E., Soegaard, H. & Batchvarova, E. 2009: Comparison of regional and ecosystem CO2 fluxes. Boreal Env. Res. 14: 204–212.
Abstract
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Laanemets, J., Zhurbas, V., Elken, J. & Vahtera, E. 2009: Dependence of upwelling-mediated nutrient transport on wind forcing, bottom topography and stratification in the Gulf of Finland: Model experiments. Boreal Env. Res. 14: 213–225.
Abstract
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Langner, J., Andersson, C. & Engardt, M. 2009: Atmospheric input of nitrogen to the Baltic Sea basin: present situation, variability due to meteorology and impact of climate change. Boreal Env. Res. 14: 226–237.
Abstract
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Rutgersson, A., Norman, M. & Åström, G. 2009: Atmospheric CO2 variation over the Baltic Sea and the impact on air–sea exchange. Boreal Env. Res. 14: 238–249.
Abstract
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Leal Filho, W. & Mannke, F. 2009: Towards policies and adaptation strategies to climate change in the Baltic Sea region — outputs of the ASTRA project. Boreal Env. Res. 14: 250–254.
Abstract
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Carlsson, B., Rutgersson, A. & Smedman, A.-S. 2009: Investigating the effect of a wave-dependent momentum flux in a process oriented ocean model. Boreal Env. Res. 14: 3–17.

New expressions of the drag coefficient were developed using measurements from the Östergarnsholm site in the Baltic Sea. The drag coefficient was significantly lower in the presence of waves travelling faster than the wind (swell). The expressions were implemented in an oceanographic process-oriented model in a 45-year simulation. Since no wave information was included we did an analysis of the potential impact of swell on an ocean model. Current velocity and surface stress were significantly altered during periods with low wind speed but the temperature and the mixing depth in the ocean were not significantly changed. The implementation of the swell effect in a process oriented ocean model is thus of limited importance. There is, however, an indication that for studies of current velocity it is crucial to have a correct description of the drag coefficient.
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Gustafsson, E. O. & Omstedt, A. 2009: Sensitivity of Baltic Sea deep water salinity and oxygen concentration to variations in physical forcing. Boreal Env. Res. 14: 18–30.

In this study, we investigate the Baltic Sea deep water exchange with focus on oxygen conditions. We assumed that the oxygen removal rate associated with decomposition of organic matter is constant, however, we use different rates for different sub-basins. The results obtained from this study of the deep water oxygen dynamics suggest a gradual increase in removal rate from the eastern Gotland Basin to the Danish Straits. Moreover, it is suggested that a drier climate would result in a reduced ventilation of the halocline region due to strong stratification. A wetter climate on the other hand is found to markedly improve the oxygen conditions in the upper deep water as a consequence of a weakened stratification and a more intense wintertime mixing.
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Jaagus, J. 2009: Regionalisation of the precipitation pattern in the Baltic Sea drainage basin and its dependence on large-scale atmospheric circulation. Boreal Env. Res. 14: 31–44.

Regionalisation of precipitation in the Baltic Sea drainage basin was realised using the principal component analysis of gridded monthly precipitations during 1900–1996 obtained from the global land precipitation dataset created in the University of East Anglia. Four main precipitation regions were determined for the Baltic Sea drainage basin: northern, eastern, southern and western. The latter contains also the Baltic Sea. Significant relationships were found between atmospheric circulation and precipitation, being the strongest in winter and the weakest in summer. Circulation variables indicating the intensity of westerlies were usually positively correlated with precipitation in windward regions during the cold part of the year. The area with the highest correlation was located in the Scandinavian Mountains. Lower positive correlations were revealed also in Denmark, southwestern Sweden, Lithuania, Latvia, Estonia, Finland and northwestern Russia. A different relationship was typical to the leeward side of westerlies in most of Sweden. Even a negative correlation was found with the circulation variables describing the intensity of westerlies. Precipitation in Sweden was mostly related to the airflow from the Baltic Sea expressed by the circulation form E. The teleconnection patterns (North Atlantic oscillation, East Atlantic, Polar/Eurasia, East Atlantic/West Russia, Scandinavian) had high correlations in specific regions at certain seasons.
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Jakobson, E., Ohvril, H. & Elgered, G. 2009: Diurnal variability of precipitable water in the Baltic region, impact on transmittance of the direct solar radiation. Boreal Env. Res. 14: 45–55.

Diurnal variations in the Integrated Precipitable Water Vapour (IPWV) are studied from GPS observations acquired at 32 sites in the Baltic region during 1996–2005. The seasonal means for spring and summer show a diurnal sinusoidal pattern of the IPWV with the maximum value in the afternoon. The peak-to-peak (PtP) value of the average diurnal IPWV cycle was 0.5 mm in the spring and 0.6 mm in the summer. In the autumn and in the winter the diurnal variations in IPWV show no clear patterns and the average PtP values of the noise-like signal are only 0.2–0.3 mm. The diurnal IPWV cycle can only be estimated by averaging data from many years because the IPWV can show fast and large variations, reaching up to 5 mm/hour during several hours. These are explained exclusively by changes in the synoptic situation and substitution of airmasses above the location of observations; two case studies with analyses of the vertical humidity profiles are presented. The impact on the transmittance of the direct solar radiation is evaluated.
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Lind, P. & Kjellström, E. 2009: Water budget in the Baltic Sea drainage basin: Evaluation of simulated fluxes in a regional climate model. Boreal Env. Res. 14: 56–67.

We investigated the Rossby Centre regional climate model, RCA3, and its ability to reproduce the water budget of the Baltic Sea drainage basin during the period from 1979 to 2002. The model was forced on its lateral boundaries with European Centre for Medium-Range Weather Forecasts Re-Analysis data, ERA40. Simulated long-term means and inter-annual variability were compared with observational records and model-derived data. The basin-wide water fluxes were broadly captured by the model, and annual mean net precipitation over land agreed well (i.e., within 5%) with observed total discharge to the Baltic Sea. Long-term annual means of precipitation were around 20% higher in RCA3 compared with reference data, the differences being in most months statistically significant at the 5% level. On the other hand, differences between the reference datasets were evident and in most months also statistically significant. The inclusion of a high-resolution dataset showed a close agreement compared with RCA3; differences were less than 5% in the long-term annual mean. Therefore, more high-resolution observational datasets, especially for evaporation and runoff, are required to refine the water budget and compare water fluxes on sub-regional and local scales.

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Tedesco, L., Vichi, M., Haapala, J. & Stipa, T. 2009: An enhanced sea-ice thermodynamic model applied to the Baltic Sea. Boreal Env. Res. 14: 68–80.

A refined Semtner 0-layer sea-ice model (ESIM1) is presented and applied to the Baltic landfast sea ice. The physical model is capable of simulating seasonal changes of snow and ice thickness. Particular attention is paid to reproducing the snow-ice and the superimposed-ice formation which play important roles in the total mass balance of the Baltic sea-ice. The model prognostic variables include all kinds of ice and snow layers that may be present during a Baltic landfast ice season and, in general, in every coastal area of an ice-covered ocean. The assessment of the model capabilities was done for 1979–1993 for four different stations in the Baltic Sea. A sensitivity test stresses the relevant role of some of the physical parameters, such as the oceanic heat flux, while a scenario analysis highlights the robustness of the model to perturbed physical forcing. Our results show that one of the key variables in modelling sea-ice thermodynamics is the snow layer and its metamorphism, and including the meteoric ice dynamics into a sea-ice model is relevant to properly simulate any ice season, also in view of climate change scenarios.

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Bhend, J. & von Storch, H. 2009: Is greenhouse gas forcing a plausible explanation for the observed warming in the Baltic Sea catchment area? Boreal Env. Res. 14: 81–88.

We investigated whether anthropogenic forcing is a plausible explanation for the observed warming in the Baltic Sea catchment area. Therefore, we compared the most recent trends in the surface temperature over land with anthropogenic climate change projections from regional climate model simulations. We analyzed patterns of change with different spatio-temporal resolutions. The observed annual area-mean change in the daily-mean temperature was consistent with the anthropogenic climate change signal. This finding was robust to the removal of the signal of the North Atlantic Oscillation. In contrast to the annual area-mean change, we found little consistency in both annual cycle and spatial variability of the observed and projected changes.
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Draveniece, A. 2009: Detecting changes in winter seasons in Latvia: the role of arctic air masses. Boreal Env. Res. 14: 89–99.

Empirical climate variability and change studies may be particularly beneficial when they combine a search for dynamic causes with the examination of trends in meteorological variables. By using an air-mass-based methodology, arctic air masses over Latvia were identified for the 1950–2005 period according to the classification used by Berliner Wetterkarte, which defines air mass types by their origin and the extent of continental or maritime influence. The frequencies of maritime, transformed and continental arctic air masses and the class of arctic air masses were examined to evaluate whether and to what extent these account for changes and variations in the surface temperature. Trends in the frequency of arctic air, monthly-average temperature and monthly lowest minimum temperature series at seven observation sites were determined by using the non-parametric Mann-Kendall test. The results indicate that the frequency of arctic air masses during winter seasons decreased significantly during this period, with the majority of the decrease being associated with maritime arctic air, and that the frequency of the bitterly cold continental arctic air has also demonstrated a decrease. This trend in the monthly frequency of arctic air was the greatest in February. The increase in the winter, near-surface air temperature was partially attributable to a decrease in maritime arctic air mass frequency and, at a seasonal scale, these changes tended to smooth the peaks in the monthly temperature time series.
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Jacob, D. & Lorenz, P. 2009: Future trends and variability of the hydrological cycle in different IPCC SRES emission scenarios — a case study for the Baltic Sea region. Boreal Env. Res. 14: 100–113.

Global climate change is also affecting the Baltic Sea and its surrounding areas. Therefore, it is of great importance to understand decadal variability and future trends as they are projected by global and regional climate change simulations. In this paper, trends and variability of hydro-meteorological quantities are investigated in simulation results for the period 1900 to 2100. Special attention is paid to the differences in the climate change signals which are simulated within three individual simulations of one IPCC SRES scenario (here: three realisations of A1B) as compared with those in three simulations of different IPCC SRES scenarios (one realisation each for A2, A1B and B1). In addition results from a validation run for 1958 to 2002 which are compared with observations, show the capability of the regional model to simulate today's climate. From the 200-year simulations it can be concluded that in all of them the differences in the hydro-meteorological quantities are of similar order, despite of significant differences in temperature trends. The relation between an increase in temperature and an intensification of the hydrological cycle is also analysed. This study shows that the differences in the IPCC SRES emission scenarios lead to significantly different temperature developments until the end of this century, but they do not stimulate significant differences in the developments of the hydrological cycles. At present this behaviour cannot be explained and needs further investigations.
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Kjellström, E. & Lind, P. 2009: Changes in the water budget in the Baltic Sea drainage basin in future warmer climates as simulated by the regional climate model RCA3. Boreal Env. Res. 14: 114–124.

In this study we investigate three different regional climate change scenarios with respect to changes in the water budget over the Baltic Sea drainage basin. The scenarios are transient climate change scenarios in which the regional climate model RCA3 has been used to downscale results from two general circulation models, with three different emissions scenarios, for the years 1961–2100. First we show that the control climate in the late 20th century is too wet as compared with observations. This wet bias in the simulations is partly attributable to biases in the forcing global models but is also amplified in the regional climate model. The future climate change signal shows a gradually warmer and wetter climate during the 21st century with increased moisture transport into the region via the atmosphere. This leads to an intensification of the hydrological cycle with more precipitation and evaporation. The net precipitation increases in all scenarios in the entire region. The changes are of the order 15%–20% for annual and areal mean fluxes.
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Madsen, K. S. & Højerslev, N. K. 2009: Long-term temperature and salinity records from the Baltic Sea transition zone. Boreal Env. Res. 14: 125–131.

The digitization of temperature and salinity data from lightships and coastal stations in the North Sea–Baltic Sea transition zone allows for multi-station and long-term studies of the oceanographic conditions of the last century. The salinity records, in combination with tide gauge records, are analyzed to demonstrate the development of a major inflow to the Baltic Sea, in terms of surface salinity, changes in stratification throughout the transition zone, and variations in the water level gradient in the zone. Also, temperature and salinity variations for years 1900–1998 are analyzed and show a 0.7 °C warming at the Drogden station towards the end of the 20th century, and no large change in salinity. The temperature change is largest in the winter and spring.
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Saue, T. & Kadaja, J. 2009: Simulated crop yield — an indicator of climate variability. Boreal Env. Res. 14: 132–142.

Biological production of plants is a complex variable, which integrates summer weather conditions. To assess summer climate variability over the last century, the concept of the meteorologically possible yield (MPY) can be used, which expresses the highest yield under existing meteorological conditions, not limited by soil quality (except its hydrological properties) or management. The MPY for early and late varieties of potato were computed with a potato-production model (POMOD) for three localities in Estonia for periods of 83–106 years. The computed yields were compared with cumulative meteorological factors and a set of the North Atlantic Oscillation indices. Significant polynomial relationships between the MPY and the cumulative meteorological elements appeared for all localities, whereas linear regression was significant only for the western coastal zone. The dual relationships, the continuously high variance around a polynomial relationship and the changes in the MPY series variability not expressible as single factors, indicate that MPY gives qualitatively new information about climatic variability in a synthesis of different factors. Correlations between the NAO index of some late autumn and winter months and MPY values were significant, albeit weak. The highest, negative correlations, expressing the effects of anticyclonic patterns, proceeded from the previous November. Positive correlations were identified for January only for a late variety of potato at an inland station.
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Sepp, M. 2009: Changes in frequency of Baltic Sea cyclones and their relationships with NAO and climate in Estonia. Boreal Env. Res. 14: 143–151.

An increase in cyclone activity and the frequency of westerlies was observed over the Baltic Sea region during the 20th century. The Baltic Sea region itself is a relatively active area of cyclogenesis. Long-term changes in the frequency and mean sea-level pressure (SLP) of cyclones formed over the Baltic Sea region were analysed in the present study using the database of cyclones from Gulev et al. (2001). Relationships between the variables of the Baltic cyclones with the NAO index and some meteorological time series in Estonia were analysed. Results showed that the total number of cyclones did not change but the number and percentage of deep cyclones increased during 1948–2002. In general, the SLP of all cyclones and SLP in tracking points decreased. Correlation analysis showed that in case of the positive phase of the NAO, less but stronger cyclones form over the Baltic region. The Baltic Sea cyclones cause milder and moister weather conditions in Estonia in winter.
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Soomere, T., Leppäranta, M. & Myrberg, K. 2009: Highlights of the physical oceanography of the Gulf of Finland reflecting potential climate changes. Boreal Env. Res. 14: 152–165.

We review highlights of the studies of physical oceanography of the Gulf of Finland, the Baltic Sea, in 1997–2007 that serve, or can be interpreted, as evidence of shifts or changes in the local climate. Also, several findings that can be used as a starting point for studies of climatic changes are described. This time interval starts from the Estonian–Finnish–Russian Year of the Gulf of Finland in 1996, a milestone of joint studies of this area that has separated two worlds since the 1940s. The studies include extensive analyses of historical and recently collected data sets, numerical modelling, and introduction of new theoretical concepts, and cover all basic disciplines of physical oceanography: hydrography, marine optics, marine meteorology, circulation, sea level, waves, and ice conditions. Their output eventually contributed to another milestone — the declaration of the Baltic Sea as a particularly sensitive sea area by the International Maritime Organization in 2005.
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Venäläinen, A., Jylhä, K., Kilpeläinen, T., Saku, S., Tuomenvirta, H., Vajda, A. & Ruosteenoja, K. 2009: Recurrence of heavy precipitation, dry spells and deep snow cover in Finland based on observations. Boreal Env. Res. 14: 166–172.

The recurrence of heavy precipitation, dry spells and deep snow cover were estimated based on observations at about ten stations in Finland during about five decades. The 10-year return levels were assessed by means of the so-called "peak over threshold" (POT) method. The return levels of the annual maximum snow depth ranged from about 65 cm in southwestern Finland to about 110 cm in Lapland. On average once in ten summers, there is likely to be a 40-day period with at most 10 mm of accumulated rain, and a period of about 75 days with less than 50 mm of rain. The average 10-year return level estimate at a fixed site was 50 ? 8 mm for daily precipitation and 139 ? 9 mm for monthly precipitation. In comparison, additional material, consisting of monthly precipitation data at about 200 stations during the past 50–150 years, suggested that once in a decade the monthly precipitation somewhere in Finland exceeds 240 ? 12 mm. The difference demonstrated the lower likelihood of an extreme event at a certain site compared with the probability that such an event occur somewhere in the country. Climate change may alter these return levels in the future.
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Graham, L. P., Olsson, J., Kjellström, E., Rosberg, J., Hellström, S.-S. & Berndtsson, R. 2009: Simulating river flow to the Baltic Sea from climate simulations over the past millennium. Boreal Env. Res. 14: 173–182.

The aim of this study was to reconstruct river flow to the Baltic Sea using data from different periods during the past thousand years. A hydrological model coupled to simulations from climate models was used to estimate river flow. A "millennium" simulation of past climate from the ECHO-G coupled atmosphere–ocean global climate model provided climatological inputs. Results from this global model were downscaled with the RCA3 regional climate model over northern Europe. Temperature and precipitation from the downscaled simulation results were then used in the HBV hydrological model to simulate river flows to the Baltic Sea for the periods 1000–1199 and 1551–1929. These were compared with observations for the period 1921–2002. A general conclusion from this work is that although climate has varied during the past millennium, variability in annual river flow to the Baltic Sea does not appear more pronounced in recent years than during the previous millennium, or vice versa.
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Kowalewska-Kalkowska, H. & Wisniewski, B. 2009: Storm surges in the Odra mouth area during the 1997–2006 decade. Boreal Env. Res. 14: 183–192.

The 1997–2006 storm surges in the Odra River mouth area (a complex structure encompassing the terminal section of the Odra split into two branches, the Szczecin Lagoon, and the inshore Pomeranian Bay in the southern Baltic Sea) were analysed to assess the impact of wind action and changes in atmospheric pressure during passages of low-pressure systems over the Baltic on the magnitude, duration, and extent of the surges. The study revealed three types of storm surges differing with respect to the dominant causative factor (baric wave, wind, and wind and baric wave combined). The baric wave-induced storm surges, recorded only at the Pomeranian Bay coast, were associated with the passage of deep and fast cyclones. The wind- and baric wave-caused storm surges coupled with an extensive system of northerly and north-westerly winds resulted in wind-driven backflow in the Odra branches. Most of the surges were recorded within November–February.
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Kundzewicz, Z. W. 2009: Adaptation to floods and droughts in the Baltic Sea basin under climate change. Boreal Env. Res. 14: 193–203.

There has been an increasing body of evidence regarding the ongoing climate change at variety of scales. Since the climate and freshwater systems are closely inter-connected, a climate change induces changes in the freshwater systems. Even if presented climate change impacts on water resources in the Baltic region are not as strong as in other areas, and some of them are advantageous, adaptation would be needed to avoid adverse impacts and to enhance beneficial effects. Adaptation strategies in the Baltic Sea region are currently at the stage of research or policy investigations. When considering adaptation, one addresses projected impacts — in much of the Baltic Sea basin, precipitation and river runoff would increase in winter, but they may decrease in summer in the south (according to some, but not all, models). There are projections of more intense summer precipitation in the Baltic region, but also more frequent summer droughts are likely. The present paper also discusses the adaptation notions and concepts, mitigation vs. adaptation, and the uncertainties.
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Gryning, S. E., Soegaard, H. & Batchvarova, E. 2009: Comparison of regional and ecosystem CO2 fluxes. Boreal Env. Res. 14: 204–212.

A budget method to derive the regional surface flux of CO2 from the evolution of the boundary layer is presented and applied. The necessary input for the method can be deduced from a combination of vertical profile measurements of CO2 concentrations by i.e. an airplane, successive radio-soundings and standard measurements of the CO2 concentration near the ground. The method was used to derive the regional flux of CO2 over an agricultural site at Zealand in Denmark during an experiment on 12–13 June 2006. The regional fluxes of CO2 represent a combination of agricultural and forest surface conditions. It was found that the regional flux of CO2 in broad terms follows the behavior of the flux of CO2 at the agricultural (grassland) and the deciduous forest station. The regional flux is comparable not only in size but also in the diurnal (daytime) cycle of CO2 fluxes at the two stations.
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Laanemets, J., Zhurbas, V., Elken, J. & Vahtera, E. 2009: Dependence of upwelling-mediated nutrient transport on wind forcing, bottom topography and stratification in the Gulf of Finland: Model experiments. Boreal Env. Res. 14: 213–225.

Numerical simulation experiments with an eddy-resolving ocean circulation model were performed to study nutrient transport to the surface layer by summer upwelling events in the Gulf of Finland. It is shown that upwelling along the southern coast of the Gulf, produced by easterly winds, brings more nutrients to the surface layer than upwelling along the northern coast produced by westerly winds of identical strength. The different ability of upwelling to transport nutrients to the surface layer along the southern and northern coasts is explained by features in the bottom topography. A steeper bottom slope and greater sea depth along the southern coast causes more nutrients to be transported to the surface layer. Offshore transport of upwelled nutrients is mostly caused by mesoscale structures — filaments and eddies. It is also shown that upwelling events along both coasts transport nutrients into the upper layer with a clear excess of phosphate. This phosphate excess might promote nitrogen-fixing cyanobacteria due to nitrogen limitation for other phytoplankton groups.
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Langner, J., Andersson, C. & Engardt, M. 2009: Atmospheric input of nitrogen to the Baltic Sea basin: present situation, variability due to meteorology and impact of climate change. Boreal Env. Res. 14: 226–237.

We present estimates of the present and future deposition of atmospheric nitrogen into the Baltic Sea made using the Eulerian chemical transport model MATCH, and compare these with earlier model estimates. The average total nitrogen deposition for periods of five to ten years from 1992 to 2001 was estimated to be in the range of 261–300 Gg N yr–1. The deposition across the whole catchment area for 2001 was estimated to be 1.55–1.73 Tg N yr–1. Inter-annual variability of nitrogen deposition into the Baltic Sea was calculated to be in the range of 5.1%–8.0%. Investigating one climate change scenario using emissions for year 2000 indicated a rather small impact on total deposition of nitrogen due to climate change, i.e. increase of total nitrogen deposition by ~5% by the end of the 21st century as compared with present conditions. The combined effect of climate change and future changes in anthropogenic emissions of nitrogen to the atmosphere remains an open question. Additional climate change scenarios using different combinations of global and regional climate models and greenhouse gas emission scenarios need to be explored.
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Rutgersson, A., Norman, M. & Åström, G. 2009: Atmospheric CO2 variation over the Baltic Sea and the impact on air–sea exchange. Boreal Env. Res. 14: 238–249.

The variability in time and space of the atmospheric molar fraction of CO2 over the Baltic Sea was investigated using data from seven stations from the World Data Center for Greenhouse Gases. The variation on a monthly timescale of CO2 was divided into a global trend, a regional anthropogenic contribution and a natural seasonal cycle. For the Baltic Sea stations the anthropogenic and terrestrial contributions were largest at the coastal sites in the southern Baltic Sea (an offset of 9 ppm), decreasing towards the north over the Baltic Sea (to about 2 ppm). When calculating the air–sea flux of CO2 using the difference in partial pressure between air and sea, uncertainties in the atmospheric molar fraction of CO2 were shown to be of secondary importance as compared with uncertainties in other parameters (< 10%). Realistic uncertainties in the sea surface partial pressure, wind speed or transfer velocity resulted in significantly larger uncertainties in a calculated air–sea flux.
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Leal Filho, W. & Mannke, F. 2009: Towards policies and adaptation strategies to climate change in the Baltic Sea region — outputs of the ASTRA project. Boreal Env. Res. 14: 250–254.

As presented at the 5th BALTEX Conference in 2007, this paper introduces the main outcomes of the project "Developing Policies & Adaptation Strategies to Climate Change in the Baltic Sea Region" (ASTRA) and discusses the results obtained from the project especially in respect of the role of policies in fostering mitigation and adaptation strategies to climate change in the Baltic Sea Region.
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