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  • 161.
    Kuznetsov, Ivan
    et al.
    SMHI, Research Department, Oceanography.
    Neumann, Thomas
    Simulation of carbon dynamics in the Baltic Sea with a 3D model2013In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 111, p. 167-174Article in journal (Refereed)
    Abstract [en]

    A full resolved three-dimensional physical-biogeochemical model ERGOM (Ecological ReGional Ocean model) was used to simulate the carbon dynamics in the Baltic Sea. Here, a simple carbon cycle has been included in the model. This was accomplished by the addition of dissolved inorganic carbon and total alkalinity to the model. Model results of the hindcast simulation (1961-2007) are in a good agreement with observations. Lateral gradients of the alkalinity are well reproduced by the model. A net inorganic carbon transport from the Baltic Sea to the Kattegat is in the range of the results of previous studies. Further, two climate projections with different nutrient load scenarios reflecting the possible development of the carbon system dynamics in the Baltic Sea were conducted. Climate scenario simulations (1961-2100) showed a continuous "acidification effect" of the Baltic Sea that mainly is controlled by changing of the atmospheric pCO(2). However, changes in pH due to other factors (such as changing temperature, primary production) are different for different regions of the sea. Simulated mean total alkalinity and dissolved inorganic carbon decrease in scenarios of climate change despite the increase of total alkalinity and dissolved inorganic carbon loads. The performed climate simulations show that mean total alkalinity decreases by about 150 mmol m(-3) and dissolved inorganic carbon by about 80-120 mmol m(-3). At the same time total alkalinity to salinity relations change in future climate due to that salinity decreases "faster" than alkalinity. Simultaneously, export of the total alkalinity and the dissolved inorganic carbon from the Baltic Sea to the North Sea has the trend to increase from 11% to 18% depending on the climate scenario. C) 2012 Elsevier B.V. All rights reserved.

  • 162.
    Löptien, Ulrike
    et al.
    SMHI, Research Department, Oceanography.
    Martensson, S.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Long-term characteristics of simulated ice deformation in the Baltic Sea (1962-2007)2013In: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, ISSN 2169-9275, Vol. 118, no 2, p. 801-815Article in journal (Refereed)
    Abstract [en]

    The North Atlantic Oscillation (NAO) index is a frequently used measure for the mean winter conditions in Northern Europe. A positive, high index is associated with strong westerlies and anomalous warm temperatures. The effects on sea ice conditions in the Baltic Sea are twofold. Warm temperatures prevent sea ice formation. If ice is present nevertheless, the strong winds can promote the formation of ice ridges which hinders ship traffic. We use an ocean-sea ice model to investigate the NAO impact on the ridged ice area fraction in the Baltic during 1962-2007. Our simulations indicate that in the northern Bothnian Bay, a high NAO index is related to an anomalous accumulation of ridges, while in the rest of the Baltic Sea, the relationship is contrary. The NAO explains locally at most only 20-25% of the ridged ice fraction interannual variability which indicates the systems complexity. However, we find high skill with local correlations around 0.8 for annually averaged ridged ice fraction reconstructed from multilinear regression using winter averaged wind extremes, surface air temperature, and sea surface temperature (SST). This suggests that the amount of ridged ice in late winter can be derived from these routinely measured quantities. In large parts of the basin, it is sufficient to use the atmospheric parameters as a predictor, while in the eastern Bothnian Bay and southern Gulf of Finland, the SST is required to reconstruct the bulk of the ridged ice fraction. Citation: Loptien, U., S. Martensson, H. E. M. Meier, and A. Hoglund (2013), Long-term characteristics of simulated ice deformation in the Baltic Sea (1962-2007), J. Geophys. Res. Oceans, 118, 801-815, doi:10.1002/jgrc.20089.

  • 163.
    Schimanke, Semjon
    et al.
    SMHI, Research Department, Oceanography.
    Spangehl, T.
    Huebener, H.
    Cubasch, U.
    Variability and trends of major stratospheric warmings in simulations under constant and increasing GHG concentrations2013In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 40, no 7-8, p. 1733-1747Article in journal (Refereed)
    Abstract [en]

    Ensemble simulations with a coupled ocean-troposphere-stratosphere model for the pre-industrial era (1860 AD), late twentieth century (1990 AD) greenhouse gas (GHG) concentrations, the SRES scenarios B1, A1B, A2, as well as stabilization experiments up to the Twenty-third century with B1 and A1B scenario GHG concentrations at their values at 2100, have been analyzed with regard to the occurrence of major sudden stratospheric warmings (SSWs). An automated algorithm using 60A degrees N and 10 hPa zonal wind and the temperature gradient between 60A degrees N and the North Pole is used to identify this phenomenon in the large data set. With 1990 CO2 concentrations (352 ppmv), the frequency of simulated SSWs in February and March is comparable to observation, but they are underestimated during November to January. All simulations show an increase in the number of SSWs from the pre-industrial period to the end of the twenty-first century, indicating that the increase of GHG is also reflected in the number of sudden warmings. However, a high variability partially masks the underlying trend. Multi-century averages during the stabilization periods indicate that the increase of SSWs is linear to the applied radiative forcing. A doubling of SSWs occurs when the GHG concentration reaches the level of the A2 scenario at the end of the twenty-first century (836 ppmv). The increase in SSWs in the projections is caused by a combination of increased wave flux from the troposphere and weaker middle atmospheric zonal winds.

  • 164.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustavsson, B.G.
    Stockholm Resilience Centre/Baltic Nest Institute, Stockholm University, Stockholm, Sweden.
    Kuznetsov, I.
    Baltic Sea Research Institute Warnemünde, Germany.
    Neumann, T.
    Leibniz-Institute for Baltic Sea Research Warnemünde, Rostock, Germany.
    Savchuk, O.P.
    Stockholm Resilience Centre/Baltic Nest Institute, Stockholm University,Stockholm, Sweden.
    Uncertainty assessment of projected ecological quality indicators in future climate2012Report (Other academic)
    Abstract [en]

    Uncertainties of projected physical key parameters and ecological quality indicators of the Baltic Sea environment, like water temperature, salinity, oxygen, nutrients and water transparency in future climate are assessed. We analyzed an ensemble of 38 scenario simulations for 1961-2099. Three state-of-the-art coupled physicalbiogeochemical models are forced with four regionalized climate projections assuming either the A1B or A2 greenhouse gas emission scenario and with four nutrient load scenarios covering the entire range from a pessimistic to a optimistic assumption of the future socioeconomic development in the Baltic Sea region. We found considerable discrepancies of projected ecological quality indicators because the sensitivities of the ecosystem response to nutrient load and temperature changes differ among the models. However, despite these uncertainties all three models agree qualitatively well in their overall response. In particular, the impact of warmer water counteracts in all models the impact of nutrient load reductions.

  • 165.
    Väli, Germo
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Elken, Jüri
    Marine Systems Institute at Tallinn University of Technology, Tallinn, Estonia.
    Simulated variations of the Baltic Sea halocline during 1961-20072012Report (Other academic)
    Abstract [en]

    The variations in the Baltic Sea salinity and the mean halocline depth during 1961-2007 are studied using Rossby Centre Ocean model. The largest trend in the monthly mean salinity averaged over the top 15 m was found in the Gulf of Riga and Baltic proper, while the trend in the northernmost part was non-existant. A period with shallow halocline in the Baltic Sea during 1970-1975 was identified and a period with deep halocline during 1990-1995 with the difference exceeding morethan 15 m in the Baltic proper between the two time-periods. Model simulation indicated that the mean surface salinity in the Baltic Sea is spatially controlled by the accumulated river runoff, while the mean salinity below the halocline in the Baltic proper by the mean zonal and absolute wind speed. The halocline depth in the Baltic Sea is affected significantly by the freshwater content and absolute wind speed. The impact of the mean zonal wind speed to the mean halocline depth in the Baltic proper is moderate, while the impact of runoff is low.

  • 166.
    Axe, Philip
    et al.
    SMHI, Research Department, Oceanography.
    Wesslander, Karin
    SMHI, Core Services.
    Kronsell, Johan
    SMHI, Core Services.
    Confidence rating for OSPAR COMP2012Report (Other academic)
    Abstract [en]

    With the adoption of the Marine Strategy Framework Directive and the Water Framework Directive, EU Member States are obliged to achieve “Good” or “Good Environmental” Status within a certain time frame, or be obliged to take remedial action. There is therefore a need to quantify the quality of the monitoring programmes on which such status assessments are based, as a part of assessing the confidence in the status assessment. Within the framework of the OSPAR Convention on the Protection of the North East Atlantic, Germany and the Netherlands presented a suggestion for how such an assessment could be made. This report documents the application of this methodology to stations in the Swedish National Monitoring Programme within the OSPAR area, and also within the Sound, which may in future be included in the Greater North Sea region under the Marine Strategy Directive. The variability of eutrophication parameters with salinity was examined. In the Kattegat, inorganic nutrient variability was least at the highest salinities, suggesting that a reliable status assessment could be made more easily with data from this region, for example, rather than in the dynamic near coast region. Assessing the coverage of the existing monitoring programme, it was found that horizontal gradients in assessment parameters (generally seasonal averages) varied by less than about 30% between stations, which suggests that the programme has reasonable spatial coverage, though additional stations would improve matters. Looking at each station individually, the current vertical sampling resolution appears adequate for most parameters, apart from chlorophyll a and inorganic nutrients during the growing season. Temporal coverage is adequate for the total nutrient concentrations, but is insufficient for the inorganic nutrients and chlorophyll a, as well as for the deep water oxygen concentration in the Sound. The poor temporal coverage of chlorophyll a and inorganic nutrients could be relatively easily improved by the addition of a two channel (nitrate + nitrite, and orthophosphate) autoanalyser onto the existing ferrybox platforms in use in these waters. Addressing these problems using traditional measuring platforms and buoys would be more costly. The poor temporal coverage of chlorophyll a and inorganic nutrients could be relatively easily improved by the addition of a two channel (nitrate + nitrite, and orthophosphate) autoanalyser onto the existing ferrybox platforms in use in these waters. Addressing these problems using traditional measuring platforms and buoys would be more costly.

  • 167.
    Schimanke, Semjon
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    The climate in the Baltic Sea region during the last millennium simulated with a regional climate model2012In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 8, no 5, p. 1419-1433Article in journal (Refereed)
    Abstract [en]

    Variability and long-term climate change in the Baltic Sea region is investigated for the pre-industrial period of the last millennium. For the first time dynamical down-scaling covering the complete millennium is conducted with a regional climate model in this area. As a result of changing external forcing conditions, the model simulation shows warm conditions in the first centuries followed by a gradual cooling until ca. 1700 before temperature increases in the last centuries. This long-term evolution, with a Medieval Climate Anomaly (MCA) and a Little Ice Age (LIA), is in broad agreement with proxy-based reconstructions. However, the timing of warm and cold events is not captured at all times. We show that the regional response to the global climate anomalies is to a strong degree modified by the large-scale circulation in the model. In particular, we find that a positive phase of the North Atlantic Oscillation (NAO) simulated during MCA contributes to enhancing winter temperatures and precipitation in the region while a negative NAO index in the LIA reduces them. In a second step, the regional ocean model (RCO-SCOBI) is used to investigate the impact of atmospheric changes onto the Baltic Sea for two 100 yr time slices representing the MCA and the LIA. Besides the warming of the Baltic Sea, the water becomes fresher at all levels during the MCA. This is induced by increased runoff and stronger westerly winds. Moreover, the oxygen concentrations in the deep layers are slightly reduced during the MCA. Additional sensitivity studies are conducted to investigate the impact of even higher temperatures and increased nutrient loads. The presented experiments suggest that changing nutrient loads may be more important determining oxygen depletion than changes in temperature or dynamic feedbacks.

  • 168. Toledano, C.
    et al.
    Cachorro, V. E.
    Gausa, M.
    Stebel, K.
    Aaltonen, V.
    Berjon, A.
    Ortiz de Galisteo, J. P.
    de Frutos, A. M.
    Bennouna, Y.
    Blindheim, S.
    Myhre, C. L.
    Zibordi, G.
    Wehrli, C.
    Kratzer, S.
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    Carlund, Thomas
    SMHI, Core Services.
    de Leeuw, G.
    Herber, A.
    Torres, B.
    Overview of sun photometer measurements of aerosol properties in Scandinavia and Svalbard2012In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 52, p. 18-28Article in journal (Refereed)
    Abstract [en]

    An overview on the data of columnar aerosol properties measured in Northern Europe is provided. Apart from the necessary data gathered in the Arctic, the knowledge of the aerosol loading in nearby areas (e.g. sub-Arctic) is of maximum interest to achieve a correct analysis of the Arctic aerosols and transport patterns. This work evaluates data from operational sites with sun photometer measurements belonging either to national or international networks (AERONET, GAW-PFR) and programs conducted in Scandinavia and Svalbard. We enumerate a list of sites, measurement type and periods together with observed aerosol properties. An evaluation and analysis of aerosol data was carried out with a review of previous results as well. Aerosol optical depth (AOD) and Angstrom exponent (AE) are the current parameters with sufficient long-term records for a first evaluation of aerosol properties. AOD (500 nm) ranges from 0.08 to 0.10 in Arctic and sub-Arctic sites (Ny-Alesund: 0.09; Andenes: 0.10; Sodankyla: 0.08), and it is somewhat higher in more populated areas in Southern Scandinavia (AOD about 0.10-0.12 at 500 nm). On the Norwegian coast, aerosols show larger mean size (AE = 1.2 at Andenes) than in Finland, with continental climate (AE = 1.5 at Sodankyla). Columnar particle size distributions and related parameters derived from inversion of sun/sky radiances were also investigated. This work makes special emphasis in the joint and collaborative effort of the various groups from different countries involved in this study. Part of the measurements presented here were involved in the IPY projects Polar-AOD and POLARCAT. (C) 2011 Elsevier Ltd. All rights reserved.

  • 169.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Arheimer, Berit
    SMHI, Research Department, Hydrology.
    Blenckner, Thorsten
    Chubarenko, Boris
    Donnelly, Chantal
    SMHI, Research Department, Hydrology.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustafsson, Bo G.
    Hansson, Anders
    Havenhand, Jonathan
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Kuznetsov, Ivan
    MacKenzie, Brian R.
    Muller-Karulis, Barbel
    Neumann, Thomas
    Niiranen, Susa
    Piwowarczyk, Joanna
    Raudsepp, Urmas
    Reckermann, Marcus
    Ruoho-Airola, Tuija
    Savchuk, Oleg P.
    Schenk, Frederik
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Vali, Germo
    Weslawski, Jan-Marcin
    Zorita, Eduardo
    Comparing reconstructed past variations and future projections of the Baltic Sea ecosystem-first results from multi-model ensemble simulations2012In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 7, no 3, article id 034005Article in journal (Refereed)
    Abstract [en]

    Multi-model ensemble simulations for the marine biogeochemistry and food web of the Baltic Sea were performed for the period 1850-2098, and projected changes in the future climate were compared with the past climate environment. For the past period 1850-2006, atmospheric, hydrological and nutrient forcings were reconstructed, based on historical measurements. For the future period 1961-2098, scenario simulations were driven by regionalized global general circulation model (GCM) data and forced by various future greenhouse gas emission and air-and riverborne nutrient load scenarios (ranging from a pessimistic 'business-as-usual' to the most optimistic case). To estimate uncertainties, different models for the various parts of the Earth system were applied. Assuming the IPCC greenhouse gas emission scenarios A1B or A2, we found that water temperatures at the end of this century may be higher and salinities and oxygen concentrations may be lower than ever measured since 1850. There is also a tendency of increased eutrophication in the future, depending on the nutrient load scenario. Although cod biomass is mainly controlled by fishing mortality, climate change together with eutrophication may result in a biomass decline during the latter part of this century, even when combined with lower fishing pressure. Despite considerable shortcomings of state-of-the-art models, this study suggests that the future Baltic Sea ecosystem may unprecedentedly change compared to the past 150 yr. As stakeholders today pay only little attention to adaptation and mitigation strategies, more information is needed to raise public awareness of the possible impacts of climate change on marine ecosystems.

  • 170.
    Höglund, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Environmentally safe areas and routes in the Baltic proper using Eulerian tracers2012In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 64, no 7, p. 1375-1385Article in journal (Refereed)
    Abstract [en]

    In recent years, the shipping of environmentally hazardous cargo has increased considerably in the Baltic proper. In this study, a large number of hypothetical oil spills with an idealized, passive tracer are simulated. From the tracer distributions, statistical measures are calculated to optimize the quantity of tracer from a spill that would stay at sea as long as possible. Increased time may permit action to be taken against the spill before the oil reaches environmentally vulnerable coastal zones. The statistical measures are used to calculate maritime routes with maximum probability that an oil spill will stay at sea as long as possible. Under these assumptions, ships should follow routes that are located south of Bornholm instead of the northern routes in use currently. Our results suggest that the location of the optimal maritime routes depends on the season, although interannual variability is too large to identify statistically significant changes. (c) 2012 Elsevier Ltd. All rights reserved.

  • 171. Jahn, A.
    et al.
    Aksenov, Y.
    de Cuevas, B. A.
    de Steur, L.
    Hakkinen, S.
    Hansen, E.
    Herbaut, C.
    Houssais, M. -N
    Karcher, M.
    Kauker, F.
    Lique, C.
    Nguyen, A.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Worthen, D.
    Zhang, J.
    Arctic Ocean freshwater: How robust are model simulations?2012In: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, ISSN 2169-9275, Vol. 117, article id C00D16Article in journal (Refereed)
    Abstract [en]

    The Arctic freshwater (FW) has been the focus of many modeling studies, due to the potential impact of Arctic FW on the deep water formation in the North Atlantic. A comparison of the hindcasts from ten ocean-sea ice models shows that the simulation of the Arctic FW budget is quite different in the investigated models. While they agree on the general sink and source terms of the Arctic FW budget, the long-term means as well as the variability of the FW export vary among models. The best model-to-model agreement is found for the interannual and seasonal variability of the solid FW export and the solid FW storage, which also agree well with observations. For the interannual and seasonal variability of the liquid FW export, the agreement among models is better for the Canadian Arctic Archipelago (CAA) than for Fram Strait. The reason for this is that models are more consistent in simulating volume flux anomalies than salinity anomalies and volume-flux anomalies dominate the liquid FW export variability in the CAA but not in Fram Strait. The seasonal cycle of the liquid FW export generally shows a better agreement among models than the interannual variability, and compared to observations the models capture the seasonality of the liquid FW export rather well. In order to improve future simulations of the Arctic FW budget, the simulation of the salinity field needs to be improved, so that model results on the variability of the liquid FW export and storage become more robust. Citation: Jahn, A., et al. (2012), Arctic Ocean freshwater: How robust are model simulations?, J. Geophys. Res., 117, C00D16, doi: 10.1029/2012JC007907.

  • 172.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Muller-Karulis, Barbel
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustafsson, Bo G.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Kuznetsov, Ivan
    SMHI, Research Department, Oceanography.
    Neumann, Thomas
    Ranjbar, Zohreh
    Savchuk, Oleg P.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Impact of Climate Change on Ecological Quality Indicators and Biogeochemical Fluxes in the Baltic Sea: A Multi-Model Ensemble Study2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 558-573Article in journal (Refereed)
    Abstract [en]

    Multi-model ensemble simulations using three coupled physical-biogeochemical models were performed to calculate the combined impact of projected future climate change and plausible nutrient load changes on biogeochemical cycles in the Baltic Sea. Climate projections for 1961-2099 were combined with four nutrient load scenarios ranging from a pessimistic business-as-usual to a more optimistic case following the Helsinki Commission's (HELCOM) Baltic Sea Action Plan (BSAP). The model results suggest that in a future climate, water quality, characterized by ecological quality indicators like winter nutrient, summer bottom oxygen, and annual mean phytoplankton concentrations as well as annual mean Secchi depth (water transparency), will be deteriorated compared to present conditions. In case of nutrient load reductions required by the BSAP, water quality is only slightly improved. Based on the analysis of biogeochemical fluxes, we find that in warmer and more anoxic waters, internal feedbacks could be reinforced. Increased phosphorus fluxes out of the sediments, reduced denitrification efficiency and increased nitrogen fixation may partly counteract nutrient load abatement strategies.

  • 173.
    Eilola, Kari
    et al.
    SMHI, Research Department, Oceanography.
    Almroth-Rosell, Elin
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Fransner, Filippa
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Modeling Nutrient Transports and Exchanges of Nutrients Between Shallow Regions and the Open Baltic Sea in Present and Future Climate2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 586-599Article in journal (Refereed)
    Abstract [en]

    We quantified horizontal transport patterns and the net exchange of nutrients between shallow regions and the open sea in the Baltic proper. A coupled biogeochemical-physical circulation model was used for transient simulations 1961-2100. The model was driven by regional downscaling of the IPCC climate change scenario A1B from two global General Circulation Models in combination with two nutrient load scenarios. Modeled nutrient transports followed mainly the large-scale internal water circulation and showed only small circulation changes in the future projections. The internal nutrient cycling and exchanges between shallow and deeper waters became intensified, and the internal removal of phosphorus became weaker in the warmer future climate. These effects counteracted the impact from nutrient load reductions according to the Baltic Sea Action Plan. The net effect of climate change and nutrient reductions was an increased net import of dissolved inorganic phosphorus to shallow areas in the Baltic proper.

  • 174. Neumann, Thomas
    et al.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustafsson, Bo
    Muller-Karulis, Barbel
    Kuznetsov, Ivan
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Savchuk, Oleg P.
    Extremes of Temperature, Oxygen and Blooms in the Baltic Sea in a Changing Climate2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 574-585Article in journal (Refereed)
    Abstract [en]

    In the future, the Baltic Sea ecosystem will be impacted both by climate change and by riverine and atmospheric nutrient inputs. Multi-model ensemble simulations comprising one IPCC scenario (A1B), two global climate models, two regional climate models, and three Baltic Sea ecosystem models were performed to elucidate the combined effect of climate change and changes in nutrient inputs. This study focuses on the occurrence of extreme events in the projected future climate. Results suggest that the number of days favoring cyanobacteria blooms could increase, anoxic events may become more frequent and last longer, and salinity may tend to decrease. Nutrient load reductions following the Baltic Sea Action Plan can reduce the deterioration of oxygen conditions.

  • 175. Gustafsson, Bo G.
    et al.
    Schenk, Frederik
    Blenckner, Thorsten
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Muller-Karulis, Barbel
    Neumann, Thomas
    Ruoho-Airola, Tuija
    Savchuk, Oleg P.
    Zorita, Eduardo
    Reconstructing the Development of Baltic Sea Eutrophication 1850-20062012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 534-548Article in journal (Refereed)
    Abstract [en]

    A comprehensive reconstruction of the Baltic Sea state from 1850 to 2006 is presented: driving forces are reconstructed and the evolution of the hydrography and biogeochemical cycles is simulated using the model BALTSEM. Driven by high resolution atmospheric forcing fields (HiResAFF), BALTSEM reproduces dynamics of salinity, temperature, and maximum ice extent. Nutrient loads have been increasing with a noteworthy acceleration from the 1950s until peak values around 1980 followed by a decrease continuing up to present. BALTSEM shows a delayed response to the massive load increase with most eutrophic conditions occurring only at the end of the simulation. This is accompanied by an intensification of the pelagic cycling driven by a shift from spring to summer primary production. The simulation indicates that no improvement in water quality of the Baltic Sea compared to its present state can be expected from the decrease in nutrient loads in recent decades.

  • 176. MacKenzie, Brian R.
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Lindegren, Martin
    Neuenfeldt, Stefan
    Eero, Margit
    Blenckner, Thorsten
    Tomczak, Maciej T.
    Niiranen, Susa
    Impact of Climate Change on Fish Population Dynamics in the Baltic Sea: A Dynamical Downscaling Investigation2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 626-636Article in journal (Refereed)
    Abstract [en]

    Understanding how climate change, exploitation and eutrophication will affect populations and ecosystems of the Baltic Sea can be facilitated with models which realistically combine these forcings into common frameworks. Here, we evaluate sensitivity of fish recruitment and population dynamics to past and future environmental forcings provided by three ocean-biogeochemical models of the Baltic Sea. Modeled temperature explained nearly as much variability in reproductive success of sprat (Sprattus sprattus; Clupeidae) as measured temperatures during 1973-2005, and both the spawner biomass and the temperature have influenced recruitment for at least 50 years. The three Baltic Sea models estimate relatively similar developments (increases) in biomass and fishery yield during twenty-first century climate change (ca. 28 % range among models). However, this uncertainty is exceeded by the one associated with the fish population model, and by the source of global climate data used by regional models. Knowledge of processes and biases could reduce these uncertainties.

  • 177. Ruoho-Airola, Tuija
    et al.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Savchuk, Oleg P.
    Parviainen, Maija
    Tarvainen, Virpi
    Atmospheric Nutrient Input to the Baltic Sea from 1850 to 2006: A Reconstruction from Modeling Results and Historical Data2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 549-557Article in journal (Refereed)
    Abstract [en]

    In this study, a consistent basin-wise monthly time series of the atmospheric nutrient load to the Baltic Sea during 1850-2006 was compiled. Due to the lack of a long time series (1850-1960) of nutrient deposition to the Baltic Sea, the data set was compiled by combining a time series of deposition data at the Baltic Nest Institute from 1970 to 2006, published historical monitoring data and deposition estimates, as well as recent modeled Representative Concentration Pathways (RCP) emission estimates. The procedure for nitrogen compounds included estimation of the deposition in a few intermediate reference years, linear interpolation between them, and the decomposition of annual deposition into a seasonal deposition pattern. As no reliable monitoring results were found for the atmospheric deposition of phosphorus during the early period of our study, we used published estimates for the temporal and spatial pattern of the phosphorus load.

  • 178.
    Hordoir, Robinson
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Effect of climate change on the thermal stratification of the baltic sea: a sensitivity experiment2012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 38, no 9-10, p. 1703-1713Article in journal (Refereed)
    Abstract [en]

    The evolution in time of the thermal vertical stratification of the Baltic Sea in future climate is studied using a 3D ocean model. Comparing periods at the end of the twentieth and twenty first centuries we found a strong increase in stratification at the bottom of the mixed layer in the northern Baltic Sea. In order to understand the causes of this increase, a sensitivity analysis is performed. We found that the increased vertical stratification is explained by a major change in re-stratification during spring solely caused by the increase of the mean temperature. As in present climate winter temperatures in the Baltic are often below the temperature of maximum density, warming causes thermal convection. Re-stratification during the beginning of spring is then triggered by the spreading of freshwater. This process is believed to be important for the onset of the spring bloom. In future climate, temperatures are expected to be usually higher than the temperature of maximum density and thermally induced stratification will start without prior thermal convection. Thus, freshwater controlled re-stratification during spring is not an important process anymore. We employed a simple box model and used sensitivity experiments with the 3D ocean model to delineate the processes involved and to quantify the impact of changing freshwater supply on the thermal stratification in the Baltic Sea. It is suggested that these stratification changes may have an important impact on vertical nutrient fluxes and the intensity of the spring bloom in future climate of the Baltic Sea.

  • 179. Martensson, S.
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Haapala, J.
    Ridged sea ice characteristics in the Arctic from a coupled multicategory sea ice model2012In: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, ISSN 2169-9275, Vol. 117, article id C00D15Article in journal (Refereed)
    Abstract [en]

    In this study, a multicategory sea ice model with explicit ice classes for ridged and rafted ice was used to examine the evolution of deformed ice during the period 1980-2002. The results show that (1) ridged ice comprises roughly 45-60% of Arctic sea ice volume and 25-45% of the sea ice area, (2) most of the perennial ice consists of ridged ice, and (3) ridged ice exhibits a small seasonal variability. Our results also show an increase in mean ridged ice thickness of 4-6 cm yr(-1) during the summer in an area north of the Canadian Archipelago and a corresponding decrease in the East Siberian Sea and Nansen Basin. At the same time, Arctic sea ice age has been observed to decline and ice drift speed to increase during the simulation period. We connect these findings with a modeled regional increase in the production rate of ridged ice. Comparison of the multicategory model and a two category reference model shows a substantially increased ice production rate due to a more frequent occurrence of leads, resulting in an ice thickness increase of up to 0.8 m. Differences in ice physics between the multicategory and reference models also affect the freshwater content. The sum of liquid and solid freshwater content in the entire Arctic Ocean is about 10% lower and net precipitation (P-E) is about 7% lower as compared to the reference model.

  • 180.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustafsson, B. G.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Modeling the combined impact of changing climate and changing nutrient loads on the Baltic Sea environment in an ensemble of transient simulations for 1961-20992012In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, no 9-10, p. 2421-2441Article in journal (Refereed)
    Abstract [en]

    The combined future impacts of climate change and industrial and agricultural practices in the Baltic Sea catchment on the Baltic Sea ecosystem were assessed. For this purpose 16 transient simulations for 1961-2099 using a coupled physical-biogeochemical model of the Baltic Sea were performed. Four climate scenarios were combined with four nutrient load scenarios ranging from a pessimistic business-as-usual to a more optimistic case following the Baltic Sea Action Plan (BSAP). Annual and seasonal mean changes of climate parameters and ecological quality indicators describing the environmental status of the Baltic Sea like bottom oxygen, nutrient and phytoplankton concentrations and Secchi depths were studied. Assuming present-day nutrient concentrations in the rivers, nutrient loads from land increase during the twenty first century in all investigated scenario simulations due to increased volume flows caused by increased net precipitation in the Baltic catchment area. In addition, remineralization rates increase due to increased water temperatures causing enhanced nutrient flows from the sediments. Cause-and-effect studies suggest that both processes may play an important role for the biogeochemistry of eutrophicated seas in future climate partly counteracting nutrient load reduction efforts like the BSAP.

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