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  • 251.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Almroth-Rosell, E.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Kniebusch, M.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Liu, Ye
    SMHI, Research Department, Oceanography.
    Väli, Germo
    SMHI, Research Department, Oceanography.
    Saraiva, S.
    Disentangling the impact of nutrient load and climate changes on Baltic Sea hypoxia and eutrophication since 1850 (vol 53, pg 1145, 2019)2019In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 53, no 1-2, p. 1167-1169Article in journal (Refereed)
  • 252.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Almroth-Rosell, Elin
    SMHI, Research Department, Oceanography.
    Climate-related changes in marine ecosystems simulated with a three-dimensional coupled physical -biogeochemical model of the Baltic Sea2011In: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 48, p. 31-55Article in journal (Refereed)
  • 253.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Almroth-Rosell, Elin
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Kniebusch, M.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Liu, Ye
    SMHI, Research Department, Oceanography.
    Väli, Germo
    SMHI, Research Department, Oceanography.
    Saraiva, S.
    Disentangling the impact of nutrient load and climate changes on Baltic Sea hypoxia and eutrophication since 18502019In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 53, no 1-2, p. 1145-1166Article in journal (Refereed)
  • 254.
    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.

  • 255.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Faxen, T
    Performance analysis of a multiprocessor coupled ice-ocean model for the Baltic Sea2002In: Journal of Atmospheric and Oceanic Technology, ISSN 0739-0572, E-ISSN 1520-0426, Vol. 19, no 1, p. 114-124Article in journal (Refereed)
    Abstract [en]

    Within the Swedish Regional Climate Modelling Programme (SWECLIM) a 3D coupled ice-ocean model for the Baltic Sea has been developed to simulate physical processes on timescales of hours to decades. The model code is based on the global ocean GCM of the Ocean Circulation Climate Advanced Modelling (OCCAM) project and has been optimized for massively parallel computer architectures. The Hibler-type dynamic-thermodynamic sea ice model utilizes elastic-viscous-plastic rheology resulting in a fully explicit numerical scheme that improves computational efficiency. A detailed performance analysis shows that the ice model causes generic workload imbalance between involved processors. An improved domain partitioning technique minimizes load imbalance, but cannot solve the problem completely. However, it is shown that the total load imbalance is not more than 13% for a mild winter and about 8% for a severe winter. With respect to parallel processor performance, the code makes the best use of available computer resources.

  • 256.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Feistel, Rainer
    Piechura, Jan
    Arneborg, Lars
    Burchard, Hans
    Fiekas, Volker
    Golenko, Nikolay
    Kuzmina, Natalia
    Mohrholz, Volker
    Nohr, Christian
    Paka, Vadim T.
    Sellschopp, Jurgen
    Stips, Adolf
    Zhurbas, Victor
    Ventilation of the Baltic Sea deep water: A brief review of present knowledge from observations and models2006In: Oceanologia, ISSN 0078-3234, Vol. 48, p. 133-164Article in journal (Refereed)
    Abstract [en]

    The ventilation of the Baltic Sea deep water is driven by either gale-forced barotropic or baroclinic salt water inflows. During the past two decades, the frequency of large barotropic inflows (mainly in winter) has decreased and the frequency of medium-intensity baroclinic inflows (observed in summer) has increased. As a result of entrainment of ambient oxygen-rich water, summer inflows are also important for the deep water ventilation. Recent process studies of salt water plumes suggest that the entrainment rates are generally smaller than those predicted by earlier entrainment models. In addition to the entrance area, the Slupsk Sill and the Slupsk Furrow are important locations for the transformation of water masses. Passing the Slupsk Furrow, both gravity-driven dense bottom flows and sub-surface cyclonic eddies, which are eroded laterally by thermohaline intrusions, ventilate the deep water of the eastern Gotland Basin. A recent study of the energy transfer from barotropic to baroclinic wave motion using a two-dimensional shallow water model suggests that about 30% of the energy needed below the halocline for deep water mixing is explained by the breaking of internal waves. In the deep water decade-long stagnation periods with decreasing oxygen and increasing hydrogen sulphide concentrations might be caused by anomalously large freshwater inflows and anomalously high mean zonal wind speeds. In different studies the typical response time scale of average salinity was estimated to be between approximately 20 and 30 years. The review summarizes recent research results and ends with a list of open questions and recommendations.

  • 257.
    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.

  • 258.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Almroth-Rosell, Elin
    SMHI, Research Department, Oceanography.
    Impact of accelerated future global mean sea level rise on hypoxia in the Baltic Sea2017In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 49, no 1-2, p. 163-172Article in journal (Refereed)
  • 259.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Kauker, F
    Modeling decadal variability of the Baltic Sea: 2. Role of freshwater inflow and large-scale atmospheric circulation for salinity2003In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 108, no C11, article id 3368Article in journal (Refereed)
    Abstract [en]

    Hindcast simulations for the period 1902 - 1998 have been performed using a three-dimensional coupled ice-ocean model for the Baltic Sea. Daily sea level observations in Kattegat, monthly basin-wide discharge data, and reconstructed atmospheric surface data have been used to force the Baltic Sea model. The reconstruction utilizes a statistical model to calculate daily sea level pressure and monthly surface air temperature, dew point temperature, precipitation, and cloud cover fields. Sensitivity experiments have been performed to explore the impact of the freshwater and saltwater inflow variability on the salinity of the Baltic Sea. The decadal variability of the average salinity is explained partly by decadal volume variations of the accumulated freshwater inflow from river runoff and net precipitation and partly by decadal variations of the large-scale sea level pressure over Scandinavia. During the last century two exceptionally long stagnation periods are found, the 1920s to 1930s and the 1980s to 1990s. During these periods, precipitation, runoff, and westerly winds were stronger, and salt transports into the Baltic were smaller than normal. As the response timescale on freshwater forcing of the Baltic Sea is about 35 years, seasonal and year-to-year changes of the freshwater inflow are too short to affect the average salinity significantly. We found that the impact of river regulation, which changes the discharge seasonality, is negligible.

  • 260.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Kauker, F
    Sensitivity of the Baltic Sea salinity to the freshwater supply2003In: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 24, no 3, p. 231-242Article in journal (Refereed)
    Abstract [en]

    The sensitivity of the Baltic Sea salinity to the freshwater supply is investigated using a 3-dimensional (3D) coupled sea-ice-ocean model. Today's climate is characterized by an average salinity of about 7.4 parts per thousand. and a freshwater supply, including river runoff and net precipitation, of about 16 000 m(3) s(-1). As recent results of some regional climate models have suggested a significant increase in precipitation in the Baltic catchment area due to anthropogenic climate change, in this study the response of salinity in the Baltic Sea to changing freshwater inflow is investigated. Of special interest is the possibility of the Baltic Sea becoming a freshwater sea with 0 parts per thousand salinity in the future. Therefore, model simulations with modified river runoff and precipitation for 1902-1998 were performed. The model is forced with daily sea-level observations in the Kattegat, monthly basin-wide discharge data, and reconstructed atmospheric surface data. The reconstruction utilizes a statistical model to calculate daily sea-level pressure, and monthly surface-air temperature, dew-point temperature, precipitation, and cloud-cover fields. It is assumed that the Kattegat deepwater salinity of about 33 parts per thousand. will not change regardless of the changed freshwater supply. In most of the experiments the final stratification is almost in a steady state after 100 yr. We found that even for a freshwater supply increased by 100% compared to 1902-1998 the Baltic Sea cannot be classified as a freshwater sea. A pronounced halocline still separates the upper and lower layers in the Baltic Proper, limiting the impact of direct wind mixing to the surface layer. A calculated phase diagram suggests that the relationship between freshwater supply and average salinity of the final steady state is non-linear. The results of the 3D model are in agreement with an analytical steady-state model assumed to work for freshwater changes smaller than 30 %. The latter model was applied in scenarios for the average salinity of the Baltic Sea.

  • 261.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Kauker, Frank
    What Causes Stagnation of the Baltic Sea Deepwater?2004In: Fourth Study Conference on BALTEX: Conference Proceedings / [ed] Hans-Jörg Isemer, Risø National Laboratory Technical University of Denmark GKSS Forschungszentrum Geesthacht GmbH , 2004, p. 172-173Conference paper (Other academic)
  • 262.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Graham, Phil
    SMHI, Research Department, Climate research - Rossby Centre.
    Estimating uncertainties of projected Baltic Sea salinity in the late 21st century2006In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 33, no 15, article id L15705Article in journal (Refereed)
    Abstract [en]

    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.

  • 263.
    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.

  • 264.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Vaeli, Germo
    Naumann, Michael
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Frauen, Claudia
    Recently Accelerated Oxygen Consumption Rates Amplify Deoxygenation in the Baltic Sea2018In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 123, no 5, p. 3227-3240Article in journal (Refereed)
  • 265. Moellmann, Christian
    et al.
    Diekmann, Rabea
    Muller-Karulis, Barbel
    Kornilovs, Georgs
    Plikshs, Maris
    Axe, Philip
    SMHI, Research Department, Oceanography.
    Reorganization of a large marine ecosystem due to atmospheric and anthropogenic pressure: a discontinuous regime shift in the Central Baltic Sea2009In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 15, no 6, p. 1377-1393Article in journal (Refereed)
    Abstract [en]

    Marine ecosystems such as the Baltic Sea are currently under strong atmospheric and anthropogenic pressure. Besides natural and human-induced changes in climate, major anthropogenic drivers such as overfishing and anthropogenic eutrophication are significantly affecting ecosystem structure and function. Recently, studies demonstrated the existence of alternative stable states in various terrestrial and aquatic ecosystems. These so-called ecosystem regime shifts have been explained mainly as a result of multiple causes, e.g. climatic regime shifts, overexploitation or a combination of both. The occurrence of ecosystem regime shifts has important management implications, as they can cause significant losses of ecological and economic resources. Because of hysteresis in ecosystem responses, restoring regimes considered as favourable may require drastic and expensive management actions. Also the Baltic Sea, the largest brackish water body in the world ocean, and its ecosystems are strongly affected by atmospheric and anthropogenic drivers. Here, we present results of an analysis of the state and development of the Central Baltic Sea ecosystem integrating hydroclimatic, nutrient, phyto- and zooplankton as well as fisheries data. Our analyses of 52 biotic and abiotic variables using multivariate statistics demonstrated a major reorganization of the ecosystem and identified two stable states between 1974 and 2005, separated by a transition period in 1988-1993. We show the change in Baltic ecosystem structure to have the characteristics of a discontinuous regime shift, initiated by climate-induced changes in the abiotic environment and stabilized by fisheries-induced feedback loops in the food web. Our results indicate the importance of maintaining the resilience of an ecosystem to atmospherically induced environmental change by reducing the anthropogenic impact.

  • 266. Moksnes, Per-Olav
    et al.
    Corell, Hanna
    Tryman, Kentaroo
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Jonsson, Per R.
    Larval behavior and dispersal mechanisms in shore crab larvae (Carcinus maenas): Local adaptations to different tidal environments?2014In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 59, no 2, p. 588-602Article in journal (Refereed)
    Abstract [en]

    Using a combination of empirical and model studies we tested whether European shore crab larvae (Carcinus maenas) from environments with different tidal regimes in the North Sea area have different swimming behaviors, and whether this affects connectivity and settlement success of larvae. Laboratory studies demonstrated the presence of an inherited tidal migration rhythm in newly hatched crab larvae from the mesotidal Danish Wadden Sea, and field studies showed that postlarvae swam in surface water almost exclusively during flood tides, suggesting that larvae use selective tidal stream transport to control the dispersal process. In contrast, shore crab larvae from microtidal Skagerrak displayed a nocturnal vertical migration behavior that appeared to switch to a diurnal behavior at the end of the postlarval phase, indicating an adaptation to avoid visual predators and to use wind-driven transport to reach shallow settlement areas. A biophysical model showed that tidal-migrating larvae in the Wadden Sea had two times higher settlement success than larvae with a diel behavior. However, no differences in settlement success were found between the two larval behaviors in microtidal Skagerrak, where lower fitness is suggested for tidal-migrating larvae due to higher predation mortality from visual predators. We suggest that the differences in inherited larval behavior in larvae from meso-and microtidal regions reflect local adaptations maintained through natural selection of successful recruits. Consistent with recent population genetic studies, modeled connectivity of shore crabs indicated an oceanographic dispersal barrier to gene flow in Eastern Wadden Sea that may facilitate such adaptations.

  • 267.
    Murthy, Ray
    et al.
    Nat. Water Res., Inst. Canada Centre for Inland Waters. Burlington, Ontario.
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    Alenius, Pekka
    Finnish Inst. of Marine Res. Helsinki.
    The Gulf of Bothnia Year-1991 – Physical transport experiments1992Report (Other academic)
  • 268. Myrberg, Kai
    et al.
    Ryabchenko, Vladimir
    Isaev, Alexei
    Vankevich, Roman
    Andrejev, Oleg
    Bendtsen, Jorgen
    Erichsen, Anders
    Funkquist, Lennart
    SMHI, Research Department, Oceanography.
    Inkala, Arto
    Neelov, Ivan
    Rasmus, Kai
    Medina, Miguel Rodriguez
    Raudsepp, Urmas
    Passenko, Jelena
    Soederkvist, Johan
    Sokolov, Alexander
    Kuosa, Harri
    Anderson, Thomas R.
    Lehmann, Andreas
    Skogen, Morten D.
    Validation of three-dimensional hydrodynamic models of the Gulf of Finland2010In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 15, no 5, p. 453-479Article in journal (Refereed)
    Abstract [en]

    A model-intercomparison study was conducted, the first of its kind for the Baltic Sea, whose aim was to systematically simulate the basic three-dimensional hydrographic properties of a realistic, complex basin. Simulations of the hydrographic features of the Gulf of Finland for the summer autumn of 1996 by six three-dimensional hydrodynamic models were compared. Validation was undertaken using more than 300 vertical hydrographic profiles of salinity and temperature. The analysis of model performance, including averaging of the ensemble results, was undertaken with a view to assessing the potential suitability of the models in reproducing the physics of the Baltic Sea accurately enough to serve as a basis for accurate simulations of biogeochemistry once ecosystem models are incorporated. The performance of the models was generally satisfactory. Nevertheless, all the models had some difficulties in correctly simulating vertical profiles of temperature and salinity, and hence mixed layer dynamics, particularly in the eastern Gulf of Finland. Results emphasized the need for high resolution in both vertical and horizontal directions in order to resolve the complex dynamics and bathymetry of the Baltic Sea. Future work needs to consider the choice of mixing and advection schemes, moving to higher resolution, high-frequency forcing, and the accurate representation of river discharges and boundary conditions.

  • 269. 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.

  • 270. Niiranen, Susa
    et al.
    Yletyinen, Johanna
    Tomczak, Maciej T.
    Blenckner, Thorsten
    Hjerne, Olle
    MacKenzie, Brian R.
    Muller-Karulis, Barbel
    Neumann, Thomas
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Combined effects of global climate change and regional ecosystem drivers on an exploited marine food web2013In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 19, no 11, p. 3327-3342Article in journal (Refereed)
    Abstract [en]

    Changes in climate, in combination with intensive exploitation of marine resources, have caused large-scale reorganizations in many of the world's marine ecosystems during the past decades. The Baltic Sea in Northern Europe is one of the systems most affected. In addition to being exposed to persistent eutrophication, intensive fishing, and one of the world's fastest rates of warming in the last two decades of the 20th century, accelerated climate change including atmospheric warming and changes in precipitation is projected for this region during the 21st century. Here, we used a new multimodel approach to project how the interaction of climate, nutrient loads, and cod fishing may affect the future of the open Central Baltic Sea food web. Regionally downscaled global climate scenarios were, in combination with three nutrient load scenarios, used to drive an ensemble of three regional biogeochemical models (BGMs). An Ecopath with Ecosim food web model was then forced with the BGM results from different nutrient-climate scenarios in combination with two different cod fishing scenarios. The results showed that regional management is likely to play a major role in determining the future of the Baltic Sea ecosystem. By the end of the 21st century, for example, the combination of intensive cod fishing and high nutrient loads projected a strongly eutrophicated and sprat-dominated ecosystem, whereas low cod fishing in combination with low nutrient loads resulted in a cod-dominated ecosystem with eutrophication levels close to present. Also, nonlinearities were observed in the sensitivity of different trophic groups to nutrient loads or fishing depending on the combination of the two. Finally, many climate variables and species biomasses were projected to levels unseen in the past. Hence, the risk for ecological surprises needs to be addressed, particularly when the results are discussed in the ecosystem-based management context.

  • 271. Nilsson, Erik
    et al.
    Rutgersson, Anna
    Dingwell, Adam
    Bjorkqvist, Jan-Victor
    Pettersson, Heidi
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Nyberg, Johan
    Stromstedt, Erland
    Characterization of Wave Energy Potential for the Baltic Sea with Focus on the Swedish Exclusive Economic Zone2019In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 5, article id 793Article in journal (Refereed)
  • 272. Nilsson, Madeleine M.
    et al.
    Kononets, M.
    Ekeroth, N.
    Viktorsson, Lena
    SMHI, Core Services.
    Hylen, A.
    Sommer, S.
    Pfannkuche, O.
    Almroth-Rosell, Elin
    SMHI, Research Department, Oceanography.
    Atamanchuk, D.
    Andersson, J. H.
    Roos, P.
    Tengberg, A.
    Hall, Per O. J.
    Organic carbon recycling in Baltic Sea sediments - An integrated estimate on the system scale based on in situ measurements2019In: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 209, p. 81-93Article in journal (Refereed)
  • 273. Olofsson, Malin
    et al.
    Robertson, Elizabeth K.
    Edler, Lars
    Arneborg, Lars
    SMHI, Research Department, Oceanography.
    Whitehouse, Martin J.
    Ploug, Helle
    Nitrate and ammonium fluxes to diatoms and dinoflagellates at a single cell level in mixed field communities in the sea2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 1424Article in journal (Refereed)
  • 274. Omstedt, A.
    et al.
    Elken, J.
    Lehmann, A.
    Lepparanta, M.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Myrberg, K.
    Rutgersson, A.
    Progress in physical oceanography of the Baltic Sea during the 2003-2014 period2014In: Progress in Oceanography, ISSN 0079-6611, E-ISSN 1873-4472, Vol. 128, p. 139-171Article, review/survey (Refereed)
    Abstract [en]

    We review progress in Baltic Sea physical oceanography (including sea ice and atmosphere-land interactions) and Baltic Sea modelling, focusing on research related to BALTEX Phase II and other relevant work during the 2003-2014 period. The major advances achieved in this period are: Meteorological databases are now available to the research community, partly as station data, with a growing number of freely available gridded datasets on decadal and centennial time scales. The free availability of meteorological datasets supports the development of more accurate forcing functions for Baltic Sea models. In the last decade, oceanographic data have become much more accessible and new important measurement platforms, such as FerryBoxes and satellites, have provided better temporally and spatially resolved observations. Our understanding of how large-scale atmospheric circulation affects the Baltic Sea climate, particularly in winter, has improved. Internal variability is strong illustrating the dominant stochastic behaviour of the atmosphere. The heat and water cycles of the Baltic Sea are better understood. The importance of surface waves in air-sea interaction is better understood, and Stokes drift and Langmuir circulation have been identified as likely playing an important role in surface water mixing in sea water. We better understand sea ice dynamics and thermodynamics in the coastal zone where sea ice interaction between land and sea is crucial. The Baltic Sea's various straits and sills are of increasing interest in seeking to understand water exchange and mixing. There has been increased research into the Baltic Sea coastal zone, particularly into upwelling, in the past decade. Modelling of the Baltic Sea-North Sea system, including the development of coupled land-sea-atmosphere models, has improved. Despite marked progress in Baltic Sea research over the last decade, several gaps remain in our knowledge and understanding. The current understanding of salinity changes is limited, and future projections of salinity evolution are uncertain. In addition, modelling of the hydrological cycle in atmospheric climate models is severely biased. More detailed investigations of regional precipitation and evaporation patterns (including runoff), atmospheric variability, highly saline water inflows, exchange between sub-basins, circulation, and especially turbulent mixing are still needed. Furthermore, more highly resolved oceanographic models are necessary. In addition, models that incorporate more advanced carbon cycle and ecosystem descriptions and improved description of water-sediment interactions are needed. There is also a need for new climate projections and simulations with improved atmospheric and oceanographic coupled model systems. These and other research challenges are addressed by the recently formed Baltic Earth research programme, the successor of the BALTEX programme, which ended in 2013. Baltic Earth will treat anthropogenic changes and impacts together with their natural drivers. Baltic Earth will serve as a network for earth system sciences in the region, following in the BALTEX tradition but in a wider context. (C) 2014 The Authors. Published by Elsevier Ltd.

  • 275.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    A sensitivity analysis of steady, free floating ice1980Report (Other academic)
    Abstract [en]

    The equation for steady, free floating ice is derived and analysed for a shallow sea. The analysis treats how accurate the free ice drift can be computed when variations in the ingoing parameters are introduced. Besides errors due to  unperfect winds, areas with large currents cause bad accuracy. If further more the bottom depth is neglected in these areas the accuracy become worse. Variable ice roughness and variable friction velocity introduce errors which are less important but still noticable in the computed ice drift.

  • 276.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    FORECASTING WATERCOOLING IN THE KATTEGAT, THE ORESUND, THE BELT SEA AND THE ARKONA BASIN1987In: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 18, no 4-5, p. 247-258Article in journal (Refereed)
  • 277.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Real-time modelling and forecasting of temperatures in the Baltic Sea1990Report (Other academic)
  • 278.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Special issue with papers presented at ''first study conference on BALTEX'' in Visby, Sweden, 28 August 1 September 1995 - Preface1996In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 48, no 5, p. 607-607Article in journal (Other academic)
  • 279.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Fourth Workshop on Baltic Sea Ice Climate. Norrköping, Sweden 22-24 May, 2002. Conference Proceedings2001Report (Other academic)
    Abstract [en]

    The Baltic Sea ice is strongly influenced by the atmospheric circulation and  shows large interannual variability. At the same time the Baltic Sea is one of the most investigated regions on earth with long ice time series. To detect trends in climate change and to relate these to natural or anthropogenic causes are of central importance in the present Baltic Sea research. This was also the main topic during the Fourth Workshop on Baltic Sea Ice Climate held in Norrköping, 22-24 May, 2002. The workshop was organised by SMHI, the SWECLIM program, the Department of Oceanography at the Earth Sciences Centre of Göteborg University, and the Swedish Maritime Administration.

  • 280.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Modeling the seasonal, interannual, and long-term variations of salinity and temperature in the Baltic proper1998In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 50, no 5, p. 637-652Article in journal (Refereed)
    Abstract [en]

    Salinity and temperature variations in the Baltic proper and the Kattegat have been analyzed with a numerical ocean model and a large amount of observational data. In the model, the Baltic Sea is divided into 13 sub-basins with high vertical resolution, horizontally coupled by barotropic and baroclinic flows and vertically coupled to a sea-ice model which includes dynamics as well as thermodynamics. The model was integrated for a 15-year period (1980-1995) by using observed meteorological forcing data, river-runoff data and sea-level data from the Kattegat. The calculated 15-year median profiles of salinity and temperature in the different sub-basins are in good agreement with observations. However, the calculated mid-depth salinities in the Arkona Basin and Bornholm Basin were somewhat overestimated, and the calculated deep-water temperatures in the Arkona Basin and the Bornholm Basin are somewhat lower than the observed values. Frontal mixing and movements in the Kattegat and the entrance area of the Arkona Basin were important to consider in the model. Water masses were simulated well, and prescribing constant deep-water properties in the Kattegat proved to be a reasonable lateral boundary condition. Further, comparisons were made between observed and calculated seasonal and interannual variations of the hydrographic properties in the Eastern Gotland Basin, as well as the interannual variations of the annual maximum ice extent. We conclude that the model can simulate these variations realistically. The major Baltic inflow of 1993 was also simulated by the model, but the inflowing water was 1-2 degrees degrees too cold. Finally, the response times to changes in forcing of the Baltic proper and the Kattegat were investigated by performing the so-called lock-exchange experiment. Typical stratification spin-up times were of the order of 10 years for the Kattegat, and 100 years for the Baltic proper.

  • 281.
    Omstedt, Anders
    et al.
    Göteborgs Universitet.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Modeling the variations of salinity and temperature in the large Gulfs of the Baltic Sea2003In: Continental Shelf Research, ISSN 0278-4343, E-ISSN 1873-6955, Vol. 23, no 3-4, p. 265-294Article in journal (Refereed)
    Abstract [en]

    The modeling of salinity and temperature in Gulf of Bothnia, Gulf of Finland, and Gulf of Riga is investigated by using a coupled sea ice-ocean Baltic Sea model. 18 years, from late 1980 to the end of 1998, have been investigated. The forcing data extracted taken from a gridded meteorological data base, sea level data from the Kattegat, and river runoff data to the different subbasins of the Baltic Sea from a hydrological data base. To improve the gridded meteorological data base a statistical model for the reduction of geostrophic winds to surface winds was developed. In the analysis it was shown that the calculated long-term salinity and temperature structures were stable and in good agreement with observations. This was made possible by using three different strait-flow models connecting the subbasins of the Baltic Sea. The seasonal and interannual variations of temperature and salinity were also well simulated by the model, implying that the coupling between the atmosphere and the Baltic Sea as well as the diapycnal mixing are reasonably well understood. The water cycle and the surface heat balance were calculated using the 18-year simulation. In the water-balance calculations it was shown that the volume flows from the large gulfs of the Baltic Sea were mainly due to baroclinic transports and that net precipitation added freshwater during the Studied period, particularly to the large gulfs. From the heat-balance calculation it is concluded that the Baltic Sea is almost in local balance with the atmosphere. The Bothnian Bay, Gulf of Finland and Gulf of Riga loose heat, whereas the Bothnian Sea gains heat, calculated as long-term means. (C) 2003 Elsevier Science Ltd. All rights reserved.

  • 282.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    CARMACK, EC
    MACDONALD, RW
    MODELING THE SEASONAL CYCLE OF SALINITY IN THE MACKENZIE SHELF ESTUARY1994In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 99, no C5, p. 10011-10021Article in journal (Refereed)
    Abstract [en]

    The freshwater content at the Mackenzie shelf/estuary is analyzed using observed and numerically simulated data. Field measurements cover the period from September 1986 to September 1987; calculations are based upon a time-dependent, one-dimensional model that treats the shelf as a single reservoir coupled to the surroundings through parameterizations of the inflows and outflows. The system is assumed to be controlled by transient Ekman flow dynamics, and forced by winds when the sea is ice free, and by tides when ice covered. Buoyancy fluxes due to river inflow, freezing and melting of ice, and outflow are added to the salinity conservation equation from which the freshwater content is calculated. Sensitivity studies from simulation of the 1986-1987 period show that the freshwater content of the Mackenzie shelf/estuary is highly influenced by freezing, ice advection off the shelf, and the wind-driven transport, all of which work effectively to remove fresh water from the shelf. Ice keels in the inner shelf may also reduce the export of fresh water to the outer shelf. The sensitivity of the system to altered river inflow from either hydroelectric development or climate change is also examined. For example, upstream storage would increase winter inflows and thus decrease the shelf's capacity to ventilate the halocline, while inflow reduction would enhance shelf ventilation.

  • 283.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Chen, D L
    Influence of atmospheric circulation on the maximum ice extent in the Baltic Sea2001In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 106, no C3, p. 4493-4500Article in journal (Refereed)
    Abstract [en]

    This work analyzes long-term changes in the annual maximum ice extent in the Baltic Sea and Skagerrak between 1720 and 1997. It focuses on the sensitivity of the ice extent to changes in air temperature and on the relationships between the ice extent and large-scale atmospheric circulation. A significant regime shift in 1877 explains the decreasing trend in the ice extent. The regime shift indicates a change from a relatively cold climate regime to a relatively warm one, which is likely a result of changed atmospheric circulation. In addition, the analysis shows that a colder climate is associated with higher variability in the ice extent and with higher sensitivity of the ice extent to changes in winter air temperature. Moreover, the ice extent is fairly well correlated with the North Atlantic Oscillation (NAO) index during winter, which supports the results of earlier studies. However, the moving correlation analysis shows that the relationship between the NAO index and the ice extent is not stationary over time. A statistical model was established that links the ice extent and a set of circulation indices. It not only confirms the importance of the zonal how but also implies the impact of meridional wind and vorticity. The usefulness of the statistical model is demonstrated by comparing its performance with that of a numerical model and with independent observations. The statistical model achieves a skill close to that of the numerical model. We conclude that this model can be a useful tool in estimating the mean conditions of the ice extent from monthly pressures, allowing for the use of the general circulation model output for predictions of mean ice extent.

  • 284. Omstedt, Anders
    et al.
    Edman, Moa
    SMHI, Research Department, Oceanography.
    Claremar, Bjorn
    Rutgersson, Anna
    SMHI, Research Department, Climate research - Rossby Centre.
    Modelling the contributions to marine acidification from deposited SOx, NOx, and NHx in the Baltic Sea: Past and present situations2015In: Continental Shelf Research, ISSN 0278-4343, E-ISSN 1873-6955, Vol. 111, p. 234-249Article in journal (Refereed)
    Abstract [en]

    We have examined the effects of historical atmospheric depositions of sulphate, nitrate, and ammonium from land and shipping on the acid-base balance in the Baltic Sea. The modelling considers the 1750-2014 period, when land and ship emissions changed greatly, with increasing carbon dioxide concentrations, SOx, NOx, and NHx emissions, and nutrient loads. The present results indicate that Baltic Sea acidification due to the atmospheric deposition of acids peaked around 1980, with a pH cumulative decrease of approximately 10(-2) in surface waters. This is one order of magnitude less than the cumulative acidification due to increased atmospheric CO2. The acidification contribution of shipping is one order of magnitude less than that of land emissions. However, the pH trend due to atmospheric acids has started to reverse due to reduced land emissions, though the effect of shipping is ongoing. The effect of strong atmospheric acids on Baltic Sea water depends on the region and period studied. The largest total alkalinity sink per surface area is in the south-western Baltic Sea where shipping is intense. Considering the entire Baltic Sea over the 2001-2010 period, the pH changes are approximately -3 x 10(-3) to -11 x 10(-3) and -4 x 10(-4) to -16 x 10(-4) pH units attributable to all emissions and ship emissions only, respectively. The corresponding changes in total alkalinity are approximately -10 to -30 mu mol kg(-1) and -1 to -4 mu mol kg(-1) attributable to all emissions and ship emissions only, respectively. (C) 2015 Elsevier Ltd. All rights reserved.

  • 285.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Gustafsson, B
    Rodhe, J
    Walin, G
    Use of Baltic Sea modelling to investigate the water cycle and the heat balance in GCM and regional climate models2000In: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 15, no 2, p. 95-108Article in journal (Refereed)
    Abstract [en]

    Results from the first simulations with the Rossby Centre regional climate atmosphere (RCA) model were used to force 2 versions of process-oriented models of the Baltic Sea-one time-dependent, the other considering the mean state. The purpose was primarily to obtain a first scenario of the future state of the Baltic Sea. In addition, we looked at this exercise as a method to evaluate the consistency of the water cycle and the heat balance produced by atmospheric climate models. The RCA model is a high-resolution atmospheric regional model which is forced with lateral conditions from a global model. A large-scale Baltic drainage basin hydrological model, forced by the RCA model, was used to simulate river runoff. Using RCA model data from the control run we found that that the temperature and ice conditions in the Baltic Sea were reasonably realistic while the salinity field was poorly reproduced. We conclude that the modelling of the water cycle needs considerable improvement. We also conclude that the time for the Baltic Sea to respond to the water cycle is much longer than the integration period so far used with the RCA model. Forcing the ocean models with RCA model data from a future scenario with an enhanced greenhouse effect gives an increased sea-surface temperature and a much reduced extent of ice in the Baltic Sea due to climate warming. Also the salinity is reduced, which implies possible serious effects on the future marine life in the Baltic Sea. The results demonstrate that accurate atmospheric modelling of not only the heat balance but also the water cycle is crucial for Baltic Sea climate simulations.

  • 286.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Meuller, Lars
    SMHI.
    Nyberg, Leif
    SMHI.
    Interannual, seasonal and regional variations of precipitation and evaporation over the Baltic Sea1997In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 26, no 8, p. 484-492Article in journal (Refereed)
    Abstract [en]

    Precipitation and evaporation rates over the Baltic Sea during the period 1981-1994 have been analyzed. The precipitation rate was based upon available meteorological weather, which were interpolated to grid paints using a two-dimensional objective analysis scheme, The evaporation rate was calculated using an ocean model, in which the Baltic Sea was treated as 13 sub-basins with high vertical resolution. Sea-surface temperatures as well as sea ice were calculated and verified extensively against temperature and ice-chart information, In the model, the latent heat flux was calculated according to a bulk formula parameterization. The evaporation rate was then calculated from the latent heat calculations and reduced by sea ice concentration, assuming that evaporation from sea ice is negligible. The long-term difference between precipitation and evaporation rates (the atmospheric fresh water inflow) is positive, which implies that the atmosphere adds fresh water to the Baltic Sea. For the period 1981 - 1994, the total mean atmospheric freshwater inflow was calculated to be 1986 m(3) s(-1). This is less than the total river runoff, but almost as large as the contribution from the River Neva, and thus an important source in the freshwater balance of the Baltic Sea. For the long time mean, the inclusion of sea ice increased (by reducing evaporation with 8%) the atmospheric freshwater inflow by 26% for the studied period, compared to an artificial case without ice in the Baltic Sea. The precipitation and evaporation over the Baltic Sea show, however, large interannual, seasonal and regional differences.

  • 287.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    MURTHY, CR
    ON CURRENTS AND VERTICAL MIXING IN LAKE-ONTARIO DURING SUMMER STRATIFICATION1994In: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 25, no 3, p. 213-232Article in journal (Refereed)
    Abstract [en]

    Currents and vertical mixing characteristics were investigated on the basis of time series of current meter and temperature data from a summer-stratified period in Lake Ontario. The experimental set up consisted of seven current meters distributed in one vertical line from 12 m below the surface to 1 m above the lake bottom at a total depth of 143 m. The period considered for the analysis was from June to September, 1991. The currents showed pronounced oscillations with two significant kinetic energy peaks, one at about 17 hours due to inertial motions, and one at 10 days, probably due to meteorological forcing. The current shear in the hypolimnion was strong enough to overcome stability and generate turbulence (Richardson numbers below 0.25) and there was probably turbulence enough available to keep the matter (almost neutral buoyant particles) in the whole Nepheloid bottom layer in suspension. In the thermocline region the turbulence was mainly damped (Richardson numbers above 1), but some events with lower Richardson numbers were also calculated indicating increased mixing during these events. By analysing filtered and unfiltered current meter data it was found that the shear-generated turbulence in the hypolimnion was mainly due to the meteorologically forced currents. In the thermocline region, however, the vertical shear associated with the inertial oscillation had a greater impact on the mixing.

  • 288.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Nyberg, Leif
    SMHI.
    A coupled ice-ocean model supporting winter navigation in the Baltic Sea: Part 2. Thermodynamics and meteorological coupling1995Report (Other academic)
  • 289.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Nyberg, Leif
    SMHI, Research Department.
    Response of Baltic Sea ice to seasonal, interannual forcing and climate change1996In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 48, no 5, p. 644-662Article in journal (Refereed)
    Abstract [en]

    The objectives of the present paper are to formulate and explore a coupled sea ice-ocean model and to examine the sensitivity of ice in the Baltic Sea to climate change. The model treats the Baltic Sea as 13 sub-basins with vertical resolution, horizontally coupled by estuarine circulation and vertically coupled to a sea ice model which includes both dynamic and thermodynamic processes. The reducing effect on the barotropic exchange due to sea ice in the entrance area is also added. The model was first verified with data from 3 test periods representing one mild, one normal and one severe ice winter. The maximum seasonal ice extent was then examined on the basis of simulated and observed data for the period 1980-1993. After that, some climate scenarios (both warm and cold) were examined. The seasonal, regional and interannual variations of sea ice were well described by the model, and the thermal response in the Baltic Sea can be realistically simulated applying forcing data from rather few stations. The Baltic Sea system is highly sensitive to climate change, particularly during the winter season, Warming may drastically decrease the number of winters classified as severe, forcing the climate towards more oceanic conditions. On the other hand, cooling will increase the number of severe winters, forcing the climate towards more sub-arctic conditions.

  • 290.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Nyberg, Leif
    SMHI, Research Department.
    Lepparanta, M
    On the ice-ocean response to wind forcing1996In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 48, no 4, p. 593-606Article in journal (Refereed)
    Abstract [en]

    The ice-ocean response to variable winds is analysed based upon two types of models. An analytical ice-ocean model with linear stress laws and forced by periodic winds is first derived. Secondly a numerical, vertically resolved ice-ocean model is introduced. In the numerical model, the ice-water stress law is calculated from a turbulence model and the wind stress is calculated on the basis of a square law formation. By comparing the ice-ocean stress law formulations, it is illustrated that the numerical model predicts an ice-ocean stress law that has a power slightly less than 2 compared to 1 for the analytical model. The numerical prediction is in good accordance with field observations and the slight deviation from 2 is due to wall effects close to the ice-water interface. It is then demonstrated that the ice-ocean response to variable winds could be well simulated by both models, but the analytical model did not capture the wind dependency properly (because of the linear approach). The ice and current factors are amplified at wind frequencies close to inertial (omega = -f) and damped at high positive and negative frequencies. The maximum ice and current factors at a wind frequency equal to the inertial oscillation are shown to be dependent only on the friction coefficients. With the constants applied in the present study, the maximum ice drift and current speed are equal to 7.8% and 5.5% of the wind speed, respectively. These steady state values are however quite unrealistic as they would require a uniformly changing wind direction for many inertial periods.

  • 291.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Nyberg, Leif
    SMHI.
    Leppäranta, Matti
    Univ. of Helsinki. Dep. of geophysics.
    A coupled ice-ocean model supporting winter navigation in the Baltic Sea: Part 1. Ice dynamics and water levels1994Report (Other academic)
  • 292.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Rutgersson, Anna
    SMHI, Research Department, Climate research - Rossby Centre.
    Closing the water and heat cycles of the Baltic Sea2000In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 9, no 1, p. 59-66Article in journal (Refereed)
    Abstract [en]

    The objective of the present paper is to analyze the water and heat cycles of the Baltic Sea. The closure equations fur the water and heat cycles are formulated and the appropriate fluxes are calculated using the ocean model PROBE-Baltic forced by meteorological fields, river runoff and sea level data from the Kattegat. The time period considered is from November 1980 to November 1995. In the closing of the water cycle it is clear that river runoff, net precipitation (precipitation minus evaporation), in- and outflows through the Baltic Sea entrance area are the dominating flows. From the ocean model it is illustrated that the long-term water balance is consistent with the salinity in the Baltic Sea and that the net precipitation is positive during the studied period. For the closing of the heat cycle, the net heat loss to the atmosphere from the open water surface, as an annual moan, is in close balance with the solar radiation. The dominating fluxes in the net heat loss to the atmosphere are the sensible heat flux, the latent heat Aux and the net long wave radiation. The heat flux from water to ice also needs to be included in the modeling efforts. Heat flows associated with precipitation in the form of rain and snow can, as annual means, be neglected as well as the heat fluxes associated with river runoff, solar radiation through the ice and ice advecting out through the Baltic Sea entrance area. The total annual mean heat loss from the water body is in close balance with the annual change of heat storage in the water and the net heat exchange through the Baltic Sea entrance area is small. This illustrates that the Baltic Sea thermodynamically responds as a closed ocean basin.

  • 293.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Sahlberg, Jörgen
    SMHI, Professional Services.
    Some results from a joint Swedish-Finnish sea ice experiment, March, 19771978Report (Other academic)
    Abstract [en]

    A joint Swedish-Finnish sea-ice experiment was performed during March 1977. Measurements in the atmosphere, ice and sea were made during six days onboard the Finnish Research vessel Aranda stationed in the ice field in the Bay of Bothnia. During two days measurements were also carried out from thetwo Swedish icebreakers Atle and Tor. This report presents the data and some results from the Swedish group.

  • 294.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Svensson, Urban
    SMHI, Research Department, Oceanography.
    ON THE MELT RATE OF DRIFTING ICE HEATED FROM BELOW1992In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 21, no 1, p. 91-100Article in journal (Refereed)
    Abstract [en]

    The melt rates of fresh and saline drifting ice, heated from below, are examined using a one-dimensional ice/ocean model with high vertical resolution. The model is based on the conservation equations for heat, salt, and momentum and uses turbulence models to achieve closure. The model includes a low-Reynolds number turbulence model for the viscous region, coupled to a high-Reynolds number turbulence model for the outer boundary, and a discrete element approach to the parameterization of roughness. It is shown that the melt rate of drifting ice is sensitive to ice roughness and molecular salt diffusion, and it is found that bulk heat transfer coefficients vary within a rather narrow range in the examined interval.

  • 295.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    WETTLAUFER, JS
    ICE GROWTH AND OCEANIC HEAT-FLUX - MODELS AND MEASUREMENTS1992In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 97, no C6, p. 9383-9390Article in journal (Refereed)
    Abstract [en]

    Heat fluxes al the ice-ocean interface and ice thickness are investigated by comparing field data from the Coordinated Eastern Arctic Experiment (CEAREX) drift phase with model calculations. The calculations are based on two types of models. The first one is a one-dimensional ice-ocean model with high vertical resolution. This model is based on the conservation equations for heat, salt, and momentum and uses turbulence models to achieve closure. A discrete element approach is also introduced to explicitly parameterize the ice roughness. The second model is a simple one-dimensional bulk heat transfer model. In this version, the interfacial salinity is modelled on the basis of salt conservation at the ice-ocean interface. The bulk heat transfer model is then calibrated using the former model. The two models predict ocean heat fluxes that are quite variable in time owing to short-term variations in the ice drift. Both models calculate realistic ice thicknesses. It is demonstrated that the observed time variation in ice thickness from eight different experimental sites with varying initial thicknesses and bottom topographies can be reproduced by applying bulk heat transfer coefficients in the range (2.8 +/- 1) x 10(-4). Horizontal variation of the thermal state within a single pack ice floe results in simultaneous freezing and melting over relatively small spatial scales. When modeling or averaging ice data in space these aspects need to be considered.

  • 296. Paczkowska, J.
    et al.
    Rowe, Of
    Schluster, L.
    Legrand, C.
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    Andersson, A.
    Allochthonous matter: an important factor shaping the phytoplankton community in the Baltic Sea2017In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 39, no 1, p. 23-34Article in journal (Refereed)
  • 297. Paetsch, Johannes
    et al.
    Burchard, Hans
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Graewe, Ulf
    Gröger, Matthias
    SMHI, Research Department, Oceanography.
    Mathis, Moritz
    Kapitza, Hartmut
    Bersch, Manfred
    Moll, Andreas
    Pohlmann, Thomas
    Su, Jian
    Ho-Hagemann, Ha T. M.
    Schulz, Achim
    Elizalde, Alberto
    Eden, Carsten
    An evaluation of the North Sea circulation in global and regional models relevant for ecosystem simulations2017In: Ocean Modelling, ISSN 1463-5003, E-ISSN 1463-5011, Vol. 116, p. 70-95Article in journal (Refereed)
  • 298.
    Pemberton, Per
    et al.
    SMHI, Research Department, Oceanography.
    Löptien, Ulrike
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Haapala, Jari
    Sea-ice evaluation of NEMO-Nordic 1.0: a NEMO-LIM3.6-based ocean-sea-ice model setup for the North Sea and Baltic Sea2017In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 10, no 8, p. 3105-3123Article in journal (Refereed)
  • 299.
    Pemberton, Per
    et al.
    SMHI, Research Department, Oceanography.
    Nilsson, J.
    The response of the central Arctic Ocean stratification to freshwater perturbations2016In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 121, no 1, p. 792-817Article in journal (Refereed)
    Abstract [en]

    Using a state-of-the-art coupled ice-ocean-circulation model, we perform a number of sensitivity experiments to examine how the central Arctic Ocean stratification responds to changes in river runoff and precipitation. The simulations yield marked changes in the cold halocline and the Arctic Atlantic layer. Increased precipitation yields a warming of the Atlantic layer, which primarily is an advective signal, propagated through the St. Anna Trough, reflecting air-sea heat flux changes over the Barents Sea. As the freshwater supply is increased, the anticyclonic Beaufort Gyre is weakened and a greater proportion of the Arctic Ocean freshwater is exported via the Fram Strait, with nearly compensating export decreases through the Canadian Arctic Archipelago. The corresponding reorganization of the freshwater pool appears to be controlled by advective processes, rather than by the local changes in the surface freshwater flux. A simple conceptual model of the Arctic Ocean, based on a geostrophically controlled discharge of the low-salinity water, is introduced and compared with the simulations. Key predictions of the conceptual model are that the halocline depth should decrease with increasing freshwater input and that the Arctic Ocean freshwater storage should increase proportionally to the square root of the freshwater input, which are in broad qualitative agreement with the sensitivity experiments. However, the model-simulated rate of increase of the freshwater storage is weaker, indicating that effects related to wind forcing and rerouting of the freshwater-transport pathways play an important role for the dynamics of the Arctic Ocean freshwater storage.

  • 300.
    Pemberton, Per
    et al.
    SMHI, Research Department, Oceanography.
    Nilsson, Johan
    Hieronymus, Magnus
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Arctic Ocean Water Mass Transformation in S-T Coordinates2015In: Journal of Physical Oceanography, ISSN 0022-3670, E-ISSN 1520-0485, Vol. 45, no 4, p. 1025-1050Article in journal (Refereed)
    Abstract [en]

    In this paper, watermass transformations in the Arctic Ocean are studied using a recently developed salinity-temperature (S-T) framework. The framework allows the water mass transformations to be succinctly quantified by computing the surface and internal diffusive fluxes in S-T coordinates. This study shows how the method can be applied to a specific oceanic region, in this case the Arctic Ocean, by including the advective exchange of water masses across the boundaries of the region. Based on a simulation with a global ocean circulation model, the authors examine the importance of various parameterized mixing processes and surface fluxes for the transformation of water across isohaline and isothermal surfaces in the ArcticOcean. The model-based results reveal a broadly realistic Arctic Ocean where the inflowing Atlantic and Pacific waters are primarily cooled and freshened before exiting back to the North Atlantic. In the model, the water mass transformation in the T direction is primarily accomplished by the surface heat flux. However, the surface freshwater flux plays a minor role in the transformation of water toward lower salinities, which is mainly driven by a downgradient mixing of salt in the interior ocean. Near the freezing line, the seasonal melt and growth of sea ice influences the transformation pattern.

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