ISSN 1239-6095 (print),   ISSN 1797-2469 (online)
© Boreal Environment Research 2012

Contents of Volume 17 no. 5

Stankūnavičius, G., Basharin, D. & Pupienis, D. 2012: Relationship between Eurasian large-scale patterns and regional climate variability over the Black and Baltic Seas. Boreal Env. Res. 17: 327–346.
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Tallberg, P., Räike, A., Lukkari, K., Leivuori, M., Lehtoranta, J. & Pitkänen, H. 2012: Horizontal and vertical distribution of biogenic silica in coastal and profundal sediments of the Gulf of Finland northeastern (Baltic Sea). Boreal Env. Res. 17: 347–362.
Abstract
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Mändla, K., Sepp, M. & Jaagus, J. 2012: Climatology of cyclones with a southern origin, and their influence on air temperature and precipitation in Estonia. Boreal Env. Res. 17: 363–376.
Abstract
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Hänninen, J. & Vuorinen, I. 2012: Comparison of several climate indices as inputs in modelling of the Baltic Sea runoff. Boreal Env. Res. 17: 377–384.
Abstract
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Hellén, H., Leck, C., Paatero, J., Virkkula, A. & Hakola, H. 2012: Summer concentrations of NMHCs in ambient air of the Arctic and Antarctic. Boreal Env. Res. 17: 385–397.
Abstract
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Keskinen, T., Lilja, J., Högmander, P., Holmes, J. A., Karjalainen, J. & Marjomäki, T. J. 2012: Collapse and recovery of the European smelt (Osmerus eperlanus) population in a small boreal lake — an early warning of the consequences of climate change. Boreal Env. Res. 17: 398–410.
Abstract
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Stankūnavičius, G., Basharin, D. & Pupienis, D. 2012: Relationship between Eurasian large-scale patterns and regional climate variability over the Black and Baltic Seas. Boreal Env. Res. 17: 327–346.

Using a NCEP/NCAR Reanalysis dataset and the empirical orthogonal function (EOF) analysis approach we studied interannual to decadal variabilities of the sea-level air pressure (SLP) and the surface air temperature (SAT) fields over Eurasiaduring the 2nd part of the 20th century. Our results agree with those of the previous studies, which conclude that Eurasian trends are the result of storm-path changes driven by the interdecadal behaviour of the NAO-like meridional dipole pattern in the Atlantic. On interannual and decadal time scales, significant synchronous correlations between correspondent modes of SAT and SLP EOF patterns were found. This fact suggests that there is a strong and stable Eurasian interrelationship between SAT and SLP large-scale fields which affects the local climate of two sub-regions: the Black and Baltic Seas. The climate variability in these sub-regions was studied in terms of Eurasian large-scale surface-temperature and air-pressure patterns responses. We concluded that the sub-regional climate variability substantially differs over the Black and Baltic Seas, and depends on different Eurasian large-scale patterns. We showed that the Baltic Sea region is influenced by the patterns arising primary from NAO-like meridional dipole, as well as Scandinavian patterns, while the Black Sea’s SAT/SLP variability is influenced mainly by the second mode EOF (eastern Atlantic) and large scale tropospheric wave structures.
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Tallberg, P., Räike, A., Lukkari, K., Leivuori, M., Lehtoranta, J. & Pitkänen, H. 2012: Horizontal and vertical distribution of biogenic silica in coastal and profundal sediments of the Gulf of Finland northeastern (Baltic Sea). Boreal Env. Res. 17: 347–362.

We studied the distribution of biogenic silica (BSi) and other potentially bio-available Si pools (NaCl-, NaBD- and NaOH-extractable Si) in short (0–25 cm) sediment cores from estuarine, coastal and open-sea areas in the Gulf of Finland (northeastern Baltic Sea). The BSi pool (150–1200 µmol g–1 DM, dry matter) was the largest potentially bio-available Si pool. In a part of the studied area, the concentration of BSi increased towards the sediment surface and could be used as an indicator of eutrophication. Several profiles were uneven due to disturbances in the sediment surface layer. The concentration of BSi was higher in the eastern (> 1000 µmol g–1 DM) than in the western Gulf of Finland (ca. 500 µmol g–1 DM). Although high estuarine retention of Si occurred, its importance in the studied area was small. High local variability in BSi concentrations probably contributes to earlier found discrepancies between external load and burial of Si in the Gulf of Finland.
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Mändla, K., Sepp, M. & Jaagus, J. 2012: Climatology of cyclones with a southern origin, and their influence on air temperature and precipitation in Estonia. Boreal Env. Res. 17: 363–376.

Cyclones with a southern origin that passed over Estonia between 1948 and 2004 were analysed in terms of their frequency, duration, and sea-level pressure. Long-term changes in these characteristics, and the influence of these cyclones on surface air temperature and precipitation, were analysed. For the purposes of this study, "southern cyclones" were defined to be the ones that formed south of 47°N and east of the 0° meridian, and entered a circle of 1000-km radius centred in Estonia. These events, which were obtained from a database of cyclones, were considered to have had an effect on weather conditions in Estonia. Although few trends were statistically significant, southern cyclones were in general found to weaken over the period studied. The number and duration of southern cyclones decreased over the period, and sea-level pressure increased. Southern cyclones induced an increase in temperature if they pass over Estonia from the west, and a decrease in temperature if they pass over Estonia from the east. On average 10% of annual precipitation in Estonia was related to cyclones with a southern origin.
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Hänninen, J. & Vuorinen, I. 2012: Comparison of several climate indices as inputs in modelling of the Baltic Sea runoff. Boreal Env. Res. 17: 377–384.

Using Transfer function (TF) models, we have earlier presented a chain of events between changes in the North Atlantic Oscillation (NAO) and their oceanographical and ecological consequences in the Baltic Sea. Here we tested whether other climate indices as inputs would improve TF models, and our understanding of the Baltic Sea ecosystem. Besides NAO, the predictors were the Arctic Oscillation (AO), sea-level air pressures at Iceland (SLP), and wind speeds at Hoburg (Gotland). All indices produced good TF models when the total riverine runoff to the Baltic Sea was used as a modelling basis. AO was not applicable in all study areas, showing a delay of about half a year between climate and runoff events, connected with freezing and melting time of ice and snow in the northern catchment area of the Baltic Sea. NAO appeared to be most useful modelling tool as its area of applicability was the widest of the tested indices, and the time lag between climate and runoff events was the shortest. SLP and Hoburg wind speeds showed largely same results as NAO, but with smaller areal applicability. Thus AO and NAO were both mostly contributing to the general understanding of climate control of runoff events in the Baltic Sea ecosystem.
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Hellén, H., Leck, C., Paatero, J., Virkkula, A. & Hakola, H. 2012: Summer concentrations of NMHCs in ambient air of the Arctic and Antarctic. Boreal Env. Res. 17: 385–397.

Summer concentrations of C2–C6 non-methane hydrocarbons (NMHCs) were measured in Antarctica and in the Arctic in 2008. The results show that NMHC concentrations are on average five times higher in the Arctic than in Antarctica. In Antarctica, there were few concentration peaks, but during most of the remaining time concentrations were below or close to the detection limits. Over the Arctic pack ice area north of 80°, concentrations of most of the measured NMHCs were always above the detection limits. No differences based on air-mass origin were detected in Antarctica, but samples collected over the central Arctic Ocean showed higher concentrations in air masses being advected from the Kara Sea and the western-central Arctic Ocean. The relatively higher NMHC-to-ethyne molar ratios calculated for samples collected over the central Arctic Ocean suggest additional alkane sources in the region.
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Keskinen, T., Lilja, J., Högmander, P., Holmes, J. A., Karjalainen, J. & Marjomäki, T. J. 2012: Collapse and recovery of the European smelt (Osmerus eperlanus) population in a small boreal lake — an early warning of the consequences of climate change. Boreal Env. Res. 17: 398–410.

We used warm summer temperatures as an analogue of climate change to estimate the potential impacts on a population of smelt (Osmerus eperlanus) in a boreal lake. A combination of hydroacoustics, seine and gillnet catches with temperature and dissolved oxygen profiles was used to study the changes in the abundance, vertical distribution and age structure of the smelt population. Smelt were squeezed between their temperature and dissolved oxygen tolerance limits during most summers. Conditions in 2002 were, however, extreme and mean surface-water temperatures exceeded 21 °C while at the same time waters below 6 m had low (< 0.5 mg l–1) dissolved oxygen concentration. Pelagic fish density during summer declined from 5000 to 200 fish ha–1. However, some young-of-the-year smelt survived in 2002, leading to a recovery in abundance to 4500 fish ha–1 by 2004. A similar recovery is not likely if the high temperature and low oxygen conditions persist during critical periods over a generation time.
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