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  • 101. Fransner, Filippa
    et al.
    Gustafsson, Erik
    Tedesco, Letizia
    Vichi, Marcello
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Roquet, Fabien
    Spilling, Kristian
    Kuznetsov, Ivan
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Morth, Carl-Magnus
    Humborg, Christoph
    Nycander, Jonas
    Non-Redfieldian Dynamics Explain Seasonal pCO(2) Drawdown in the Gulf of Bothnia2018In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 123, no 1, p. 166-188Article in journal (Refereed)
  • 102. Fransner, Filippa
    et al.
    Nycander, Jonas
    Morth, Carl-Magnus
    Humborg, Christoph
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Gustafsson, Erik
    Deutsch, Barbara
    Tracing terrestrial DOC in the Baltic SeaA 3-D model study2016In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 30, no 2, p. 134-148Article in journal (Refereed)
    Abstract [en]

    The fate of terrestrial organic matter brought to the coastal seas by rivers and its role in the global carbon cycle are still not very well known. Here the degradation rate of terrestrial dissolved organic carbon (DOCter) is studied in the Baltic Sea, a subarctic semienclosed sea, by releasing it as a tracer in a 3-D circulation model and applying linear decay constants. A good agreement with available observational data is obtained by parameterizing the degradation in two rather different ways: one by applying a decay time on the order of 10years to the whole pool of DOCter and one by dividing the DOCter into onerefractory pool and one pool subject to a decay time on the order of 1year. The choice ofparameterization has asignificant effect on where in the Baltic Sea the removal takes place, which can be of importance whenmodeling the full carbon cycle and the CO2 exchange with the atmosphere. In both cases the biogeochemical decayoperates on time scales less than the water residence time. Therefore, only a minor fraction of the DOCter reaches the North Sea, whereas approximately 80% is removed by internal sinks within the Baltic Sea. This further implies that DOCter mineralization is an important link in land-sea-atmosphere cycling of carbon in coastal and shelf seas that are heavily influenced by riverine DOC.

  • 103.
    Fransson, L.
    et al.
    SMHI.
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Stehn, L.
    SMHI.
    Sea ice properties studied from the ice-breaker Tor during BEPERS-881989Report (Other academic)
  • 104. Fredriksson, S. T.
    et al.
    Arneborg, Lars
    SMHI, Research Department, Oceanography.
    Nilsson, H.
    Handler, R. A.
    Surface shear stress dependence of gas transfer velocity parameterizations using DNS2016In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 121, no 10, p. 7369-7389Article in journal (Refereed)
  • 105.
    Funquist, Lennart
    SMHI, Research Department, Oceanography.
    An operational Baltic Sea circulation model: Part 1. Barotropic version1993Report (Other academic)
  • 106.
    Funquist, Lennart
    SMHI, Research Department, Oceanography.
    En hydrodynamisk modell för spridnings- och cirkulationsberäkningar i Östersjön: Slutrapport1985Report (Other academic)
    Abstract [sv]
    • En modell för beräkning av föroreningars spridning i Östersjön har utvecklats vid SMHI
    • Modellen behandlar spridning såväl horisontellt som vertikal och kan användas för spridningsstudier i en tidsskala från timmar till år.
    • Biokemiska förlopp kan utan svårighet inkluderas 1 modellen.
    • Modellen är ett lämpligt redskap för studier av pågående utsläpp, katastrofutsläpp och i samband med industrilokalisering.
    • Kustområden med återkommande uppvällning kan identifieras med hjälp av modellen.
    • Cirkulationsmodellen ger ett värdefullt bidrag till den allmänna kunskapen om Östersjöns dynamik.
  • 107.
    Funquist, Lennart
    SMHI, Research Department, Oceanography.
    Numerisk beräkning av vågor i kraftverksdammar1987Report (Other academic)
    Abstract [sv]

    Kraftiga vågrörelser uppstår i kraftverksmagasin,  när avtappningen hastigt stryps. Detta kan vara fallet vid störningar i kraftverksdriften eller eldistributionsnätet.Om vattennivån i magasinet ligger nära dämningsgränsen, kan vågorna orsaka störningar i ytregleringsautomatiken och katastrofskyddet, samtidigt som dämningsgränsen kan överskridas. Liknande problem kan uppstå i korttidsreglerade magasin.Amplituder på upp till o.60 m har registrerats just vid utloppet (Stugun), medan längre uppströms endast registreras vågor med en amplitud mindre än 0.15 m. Initialt bildas vågor av flera frekvenser, och de högfrekventa och med högst  amplitud dämpas mycket kraftigt och försvinner efter 100 - 200 m. Vattenståndshöjningen, som orsakas av det plötsliga stoppet, är emellertid synlig i hela magasinet som en solitär våg med en amplitud av upp till 0.20 m. Dessutom uppstår egensvängningar i delbassänger nära utloppet med en amlitud på 0.05 - 0.15 m, vilket kan vara nog för att i vissa fall överskrida dämningsgränsen.Avsikten med den här redovisade studien är att utröna huruvida uppmätta vågor går att reproducera i en numerisk modell, och vidare om modellen kan tillämpas på godtyckligt magasin för studier av effekten av dessa vågor.

  • 108.
    Funquist, Lennart
    et al.
    SMHI, Research Department, Oceanography.
    Eckhard, Kleine
    SMHI.
    An introduction to HIROMB, an operational baroclinic model for the Baltic Sea2007Report (Other academic)
    Abstract [en]

    A3-dimensional baroclinic model of the North Sea and the Baltic Sea, designed for a daily operational use is described in detail. The model is based on a similar model running in operational mode at the German Federal Maritime and Hydrographic Agency (BSH) in Hamburg, Germany. The operational forecasts started in 1995 with a daily 24-hour forecast and was later extended to 48 hours. The model is mainly forced by SMHI's operational atmospheric model (HIRLAM), but also by river runoff from an operational hydrological model and wave radition stress from a wind wave model. The present version of the model is set up on a nested grid where a 12 nautical mile (nm) grid covers the whole area while Skagerrak, Kattegat, the Belt Sea and the Baltic Sea are covered with a 1 nm grid. A parallelized version of the model has been developed and runs on a distributed memory parallel computer.

  • 109.
    Funquist, Lennart
    et al.
    SMHI, Research Department, Oceanography.
    Gidhagen, Lars
    SMHI, Research Department, Air quality.
    Svensson, Urban
    SMHI, Research Department, Oceanography.
    THE MATHEMATICAL-MODELING OF BAROCLINIC WAVES AND FRONTS IN THE OCEAN1987In: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 11, no 1, p. 11-18Article in journal (Refereed)
  • 110.
    Funquist, Lennart
    et al.
    SMHI, Research Department, Oceanography.
    Kleine, Eckhard
    SMHI.
    Application of the BSH model to Kattegat and Skagerrak1995Report (Other academic)
  • 111.
    Funquist, Lennart
    et al.
    SMHI, Research Department, Oceanography.
    Ljungemyr, Patrik
    SMHI, Core Services.
    Validation of HIROMB during 1995-961997Report (Other academic)
    Abstract [en]

    IROMB (High Resolution Operational Model of the Baltic Sea) is the result of a combined effort between BSH (Bundesamt för Seeschiffahrt und Hydrographie) and SMHI (Swedish Meteorological and Hydrological Institute). In its present form, the model is a modified version of the BSH operational model (Kleine, 1994) with identical boundaries to the North Atlantic. The cooperation started in summer 1994 when the model was set up at SMHI. The first operational runs started in the sumrner 1995 and since then the model has been running daily except fora limited number of periods when there were no meteorological input from the HIRLAM (atmospheric) model available because of computer problems. During the first months, some occasions with stability problems occurred, leading toa restart from the climatological fields.

    This report presents results from a continous verification exercise, where model results are compared to observations of water level, surface temperature, currents, ice thickness and salinity and temperature profiles. The times series data are taken from the period September-November 1996 while the ice thickness data are from November and December 1996 and the sea surface temperature data are taken from August, November and December 1996.

    For a detailed description of the model, the reader is referred to a forthcoming report by Funkquist and Kleine.

  • 112. Gastgifvars, Maria
    et al.
    Mueller-Navarra, Sylvin
    Funkquist, Lennart
    SMHI, Research Department, Oceanography.
    Huess, Vibeke
    Performance of operational systems with respect to water level forecasts in the Gulf of Finland2008In: Ocean Dynamics, ISSN 1616-7341, E-ISSN 1616-7228, Vol. 58, no 2, p. 139-153Article in journal (Refereed)
    Abstract [en]

    This paper is devoted to the validation of water level forecasts in the Gulf of Finland. Daily forecasts produced by four setups of operational, three-dimensional Baltic Sea oceanographic models are analyzed using statistical means and are compared with water level observations at three Finnish stations located on the northern coast of the Gulf of Finland. The overall conclusion is that the operational systems were skillful in forecasting water level variations during the study period from November 1, 2003, to January 31, 2005. The factors causing differences between the water level forecasts of different models are discussed as well. An important task of operational sea level forecasting services is to provide accurate and early information about extreme water levels, both positive and negative surges. During the study period, two major winter storms occurred which caused coastal flooding in the region. According to our analysis, the operational models forecast the rise of water levels during these events rather successfully. Nowadays, operational forecasts can provide early warnings of extreme water levels at least 1 day in advance, which may be regarded as a minimum requirement for an operational forecasting system. The paper concludes that the models generally performed very well, with over 93% of the hourly water level forecasts found to be within the range of +/- 15 cm of the observed water levels, and with the timing of the water level peaks accurately predicted. Further discussion and studies dealing with the assessment of the skills of both operational meteorological and oceanographic forecasts, especially in connection with rare surge events, will be necessary. Skill assessment of operational oceanographic models would be relatively easy if acceptable error limits or a quality system was developed for the Baltic Sea operational models.

  • 113.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Funquist, Lennart
    SMHI, Research Department, Oceanography.
    Murthy, Ray
    SMHI.
    Calculations of horizontal exchange coefficients using Eulerian time series current meter data from the Baltic Sea1986Report (Other academic)
  • 114. Godhe, Anna
    et al.
    Cusack, Caroline
    Pedersen, John
    Andersen, Per
    Anderson, Donald M.
    Bresnan, Eileen
    Cembella, Allan
    Dahl, Einar
    Diercks, Sonja
    Elbraechter, Malte
    Edler, Lars
    SMHI, Research Department, Oceanography.
    Galluzzi, Luca
    Gescher, Christine
    Gladstone, Melissa
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    Kulis, David
    LeGresley, Murielle
    Lindahl, Odd
    Marin, Roman
    McDermott, Georgina
    Medlin, Linda K.
    Naustvoll, Lars-Johan
    Penna, Antonella
    Toebe, Kerstin
    Intercalibration of classical and molecular techniques for identification of Alexandrium fundyense (Dinophyceae) and estimation of cell densities2007In: Harmful Algae, ISSN 1568-9883, E-ISSN 1878-1470, Vol. 6, no 1, p. 56-72Article in journal (Refereed)
    Abstract [en]

    A workshop with the aim to compare classical and molecular techniques for phytoplankton enumeration took place at Kristineberg Marine Research Station, Sweden, in August 2005. Seventeen different techniques - nine classical microscopic-based and eight molecular methods - were compared. Alexandrium fundyense was the target organism in four experiments. Experiment 1 was designed to determine the range of cell densities over which the methods were applicable. Experiment 2 tested the species specificity of the methods by adding Alexandrium ostenfeldii, to samples containing A. fundyense. Experiments 3 and 4 tested the ability of the methods to detect the target organism within a natural phytoplankton community. Most of the methods could detect cells at the lowest concentration tested, 100 cells L-1, but the variance was high for methods using small volumes, such as counting chambers and slides. In general, the precision and reproducibility of the investigated methods increased with increased target cell concentration. Particularly molecular methods were exceptions in that their relative standard deviation did not vary with target cell concentration. Only two of the microscopic methods and three of the molecular methods had a significant linear relationship between their cell count estimates and the A. fundyense concentration in experiment 2, where the objective was to discriminate that species from a morphologically similar and genetically closely related species. None of the investigated methods were affected by the addition of a natural plankton community background matrix in experiment 3. The results of this study are discussed in the context of previous intercomparisons and the difficulties in defining the absolute, true target cell concentration. (c) 2006 Elsevier B.V. All rights reserved.

  • 115. Godhe, Anna
    et al.
    Egardt, Jenny
    Kleinhans, David
    Sundqvist, Lisa
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Jonsson, Per R.
    Seascape analysis reveals regional gene flow patterns among populations of a marine planktonic diatom2013In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 280, no 1773, article id 20131599Article in journal (Refereed)
    Abstract [en]

    We investigated the gene flow of the common marine diatom, Skeletonema marinoi, in Scandinavian waters and tested the null hypothesis of panmixia. Sediment samples were collected from the Danish Straits, Kattegat and Skagerrak. Individual strains were established from germinated resting stages. A total of 350 individuals were genotyped by eight microsatellite markers. Conventional F-statistics showed significant differentiation between the samples. We therefore investigated whether the genetic structure could be explained using genetic models based on isolation by distance (IBD) or by oceanographic connectivity. Patterns of oceanographic circulation are seasonally dependent and therefore we estimated how well local oceanographic connectivity explains gene flow month by month. We found no significant relationship between genetic differentiation and geographical distance. Instead, the genetic structure of this dominant marine primary producer is best explained by local oceanographic connectivity promoting gene flow in a primarily south to north direction throughout the year. Oceanographic data were consistent with the significant FST values between several pairs of samples. Because even a small amount of genetic exchange prevents the accumulation of genetic differences in F-statistics, we hypothesize that local retention at each sample site, possibly as resting stages, is an important component in explaining the observed genetic structure.

  • 116. Goerlandt, Floris
    et al.
    Goite, Habtamnesh
    Banda, Osiris A. Valdez
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Ahonen-Rainio, Paula
    Lensu, Mikko
    An analysis of wintertime navigational accidents in the Northern Baltic Sea2017In: Safety Science, ISSN 0925-7535, E-ISSN 1879-1042, Vol. 92, p. 66-84Article in journal (Refereed)
  • 117. Golbeck, Inga
    et al.
    Li, Xin
    Janssen, Frank
    Bruening, Thorger
    Nielsen, Jacob W.
    Huess, Vibeke
    Soderkvist, Johan
    Buchmann, Bjarne
    Siiria, Simo-Matti
    Vaha-Piikkio, Olga
    Hackett, Bruce
    Kristensen, Nils M.
    Engedahl, Harald
    Blockley, Ed
    Sellar, Alistair
    Lagemaa, Priidik
    Ozer, Jose
    Legrand, Sebastien
    Ljungemyr, Patrik
    SMHI, Core Services.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Uncertainty estimation for operational ocean forecast products-a multi-model ensemble for the North Sea and the Baltic Sea2015In: Ocean Dynamics, ISSN 1616-7341, E-ISSN 1616-7228, Vol. 65, no 12, p. 1603-1631Article in journal (Refereed)
    Abstract [en]

    Multi-model ensembles for sea surface temperature (SST), sea surface salinity (SSS), sea surface currents (SSC), and water transports have been developed for the North Sea and the Baltic Sea using outputs from several operational ocean forecasting models provided by different institutes. The individual models differ in model code, resolution, boundary conditions, atmospheric forcing, and data assimilation. The ensembles are produced on a daily basis. Daily statistics are calculated for each parameter giving information about the spread of the forecasts with standard deviation, ensemble mean and median, and coefficient of variation. High forecast uncertainty, i.e., for SSS and SSC, was found in the Skagerrak, Kattegat (Transition Area between North Sea and Baltic Sea), and the Norwegian Channel. Based on the data collected, longer-term statistical analyses have been done, such as a comparison with satellite data for SST and evaluation of the deviation between forecasts in temporal and spatial scale. Regions of high forecast uncertainty for SSS and SSC have been detected in the Transition Area and the Norwegian Channel where a large spread between the models might evolve due to differences in simulating the frontal structures and their movements. A distinct seasonal pattern could be distinguished for SST with high uncertainty between the forecasts during summer. Forecasts with relatively high deviation from the multi-model ensemble (MME) products or the other individual forecasts were detected for each region and each parameter. The comparison with satellite data showed that the error of the MME products is lowest compared to those of the ensemble members.

  • 118.
    Graham, Phil
    et al.
    SMHI, Professional Services.
    Chen, Deliang
    Bøssing Christensen, Ole
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Krysanova, Valentina
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Radziejewski, Maciej
    Räisänen, Jouni
    Rockel, Burkhardt
    Ruosteenoja, Kimmo
    Projections of Future Anthropogenic Climate Change2008In: Assessment of Climate Change for the Baltic Sea Basin / [ed] The BACC Author Team, Springer, Berlin , 2008, p. 133-219Chapter in book (Other academic)
  • 119. Granhag, Lena
    et al.
    Moller, Lene Friis
    Hansson, Lars J.
    SMHI, Research Department, Oceanography.
    Size-specific clearance rates of the ctenophore Mnemiopsis leidyi based on in situ gut content analyses2011In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 33, no 7, p. 1043-1052Article in journal (Refereed)
    Abstract [en]

    The ctenophore Mnemiopsis leidyi can consume large amounts of zooplankton prey. However, quantitative measurements of feeding rates, based on field data, are scarce. We measured the time required by the invasive M. leidyi to digest naturally occurring prey species in the Gullmar fjord, Sweden. Digestion times were related to prey size and type, number of prey in the gut and size of the predator. Large prey species or many prey in the gut resulted in longer digestion times compared with small or few prey, but digestion time also varied with the size of M. leidyi. The prey-and predator-specific digestion times were used together with in situ prey concentrations and gut contents of M. leidyi to calculate the clearance rates. Clearance rate as a function of ctenophore size is presented for the most abundant mesozooplankton: Acartia sp., Oithona sp., Oikopleura dioica and Penilia avirostris. On the basis of the relation between digestion time and the carbon content ratio between prey and predator, we discuss the possible effects of mixed prey assemblages on the estimates of clearance rates.

  • 120.
    Groger, Matthias
    et al.
    SMHI, Research Department, Oceanography.
    Arneborg, Lars
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Summer hydrographic changes in the Baltic Sea, Kattegat and Skagerrak projected in an ensemble of climate scenarios downscaled with a coupled regional ocean-sea ice-atmosphere model2019In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 53, no 9-10, p. 5945-5966Article in journal (Refereed)
  • 121. Groger, Matthias
    et al.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Thermal air-sea coupling in hindcast simulations for the North Sea and Baltic Sea on the NW European shelf2015In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 67, article id 26911Article in journal (Refereed)
    Abstract [en]

    This article compares interactively coupled atmosphere-ocean hindcast simulations with stand-alone runs of the atmosphere and ocean models using the recently developed regional ocean-atmosphere model NEMO-Nordic for the North Sea and Baltic Sea. In the interactively coupled run, the ocean and the atmosphere components were allowed to exchange mass, momentum and heat every 3 h. Our results show that interactive coupling significantly improves simulated winter sea surface temperatures (SSTs) in the Baltic Sea. The ocean and atmosphere stand-alone runs, respectively, resulted in too low sea surface and air temperatures over the Baltic Sea. These two runs suffer from too cold prescribed ERA40 SSTs, which lower air temperatures and weaken winds in the atmosphere only run. In the ocean-only run, the weaker winds additionally lower the vertical mixing thereby lowering the upward transport of warmer subpycnocline waters. By contrast, in the interactively coupled run, the ocean-atmosphere heat exchange evolved freely and demonstrated good skills in reproducing observed surface temperatures. Despite the strong impact on oceanic and atmospheric variables in the coupling area, no far reaching influence on atmospheric variables over land can be identified. In perturbation experiments, the different dynamics of the two coupling techniques is investigated in more detail by implementing strong positive winter temperature anomalies in the ocean model. Here, interactive coupling results in a substantially higher preservation of heat anomalies because the atmosphere also warmed which damped the ocean to atmosphere heat transfer. In the passively coupled set-up, this atmospheric feedback is missing, which resulted in an unrealistically high oceanic heat loss. The main added value of interactive air-sea coupling is twofold: (1) the elimination of any boundary condition at the air-sea interface and (2) the more realistic dynamical response to perturbations in the ocean-atmosphere heat balance, which will be essential in climate warming scenarios.

  • 122. 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.

  • 123.
    Gustafsson, Nils
    et al.
    SMHI, Research Department, Meteorology.
    Nyberg, Leif
    SMHI.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Coupling of a high-resolution atmospheric model and an ocean model for the Baltic Sea1998In: Monthly Weather Review, ISSN 0027-0644, E-ISSN 1520-0493, Vol. 126, no 11, p. 2822-2846Article in journal (Refereed)
    Abstract [en]

    The coupling between a high-resolution weather forecasting model and an ocean model is investigated. It is demonstrated by several case studies that improvements of short-range weather forecasting in the area of the Baltic Sea require an accurate description of the lower boundary condition over sea. The examples are taken from summer situations without sea ice as well as from winter situations with extreme sea ice conditions. It is shown that the sea state variables used in the model influence the weather forecast both directly on the local scale due to the local impact of surface fluxes of latent and sensible heat and on regional and larger scales. The convective snowbands during winters with cold airmass outbreaks over the open water surfaces of the Baltic Sea are extreme examples of the influence of sea state variables on a regional scale, It is furthermore demonstrated that the sea state conditions may change considerably within forecasting periods up to 48 h. This implies the necessary application of ocean models, two-way interactively coupled to the weather forecasting model. The coupling of an advanced 2.5-dimensional ice-ocean model to the operational Swedish Meteorological and Hydrological Institute (SMHI) weather forecasting model HIRLAM is described. The ice-ocean model includes two-dimensional, horizontally resolved ice and storm surge models and a one-dimensional, vertically resolved ocean model applied to 31 Baltic Sea regions. The coupled model system is applied operationally in a data assimilation system at the SMHI. No data assimilation is applied in the operational ocean component: manual modifications to the sea state variables are introduced a few times every winter season. The application of this operational coupled model data assimilation system to the mesoscale reanalysis for the Baltic Sea Experiment (BALTEX) shows that it is necessary to apply data assimilation fur the sea state variables in order to avoid drift of the coupled model system toward less realistic model states. A successful application of a simple assimilation of SST observations is presented. The observed SSTs are first subject to a horizontal filter in order to minimize the effects of observational errors and to restrict the influence to a larger horizontal scale. Then the differences between these filtered temperature observations and the model SSTs are used to construct a modified sensible heat Aux that is applied as a form of a "nudging" term to the ocean model. It turns out that this "nudging" is successful in avoiding the drift away from realistic sea state conditions. The described atmosphere and ocean data assimilation scheme has been applied in a rerun of the BALTEX mesoscale reanalysis for the cold winter 1986/87. The quality of this reanalysis was assessed through the successful simulation of the convective snowbands in January 1987.

  • 124. Haapala, J
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Rinne, J
    Numerical investigations of future ice conditions in the Baltic Sea2001In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 30, no 4-5, p. 237-244Article in journal (Refereed)
    Abstract [en]

    Global climate change is expected to have an effect on the physical and ecological characteristics of the Baltic Sea. Estimates of future climate on the regional scale can be obtained by using either statistical or dynamical downscaling methods of global AOGCM scenario results. In this paper, we use 2 different coupled ice-ocean models of the Baltic Sea to simulate present and future ice conditions around 100 years from present. Two 10-year time slice experiments have been performed using the results of atmospheric climate model simulations as forcing, one representing pre-industrial climate conditions (control simulation), and the other global warming with a 150% increase in CO2 greenhouse gas concentration (scenario simulation). Present-day climatological ice conditions and interannual variability are realistically reproduced by the models. The simulated range of the maximum annual ice extent in the Baltic in both models together is 180 to 420.10(3) km(2) in the control simulation and 45 to 270.10(3) km(2) in the scenario simulation. The range of the maximum annual ice thickness is from 32 to 96 cm and from 11 to 60 cm in the control and scenario simulations, respectively. In contrast to earlier estimates, sea ice is still formed every winter in the Northern Bothnian Bay and in the most Eastern parts of the Gulf of Finland. Overall, the simulated changes of quantities such as ice extent and ice thickness, as well as their interannual variations are relatively similar in both models, which is remarkable, because the 2 coupled ice-ocean model systems have been. developed independently. This increases the reliability of future projections of ice conditions in the Baltic Sea.

  • 125. Hajdu, S
    et al.
    Edler, Lars
    SMHI, Research Department, Oceanography.
    Olenina, I
    Witek, B
    Spreading and establishment of the potentially toxic dinoflagellate Prorocentrum minimum in the Baltic Sea2000In: International review of hydrobiology, ISSN 1434-2944, E-ISSN 1522-2632, Vol. 85, no 5-6, p. 561-575Article in journal (Refereed)
    Abstract [en]

    During the last two decades the potentially toxic dinoflagellate Prorocentrum minimum (PAVILLARD) SCHILLER has successfully established itself in the Baltic Sea. It is now a dominant summer species in the southern Baltic proper, and reaches as far into the low salinity of the northern Baltic as the central Gulf of Finland. In the 1990s, it developed several coastal blooms in the eastern and northern Baltic proper, but occurred irregularly between years. Field data show that P. minimum can grow at salinities below 5 PSU, confirming its potential to penetrate farther into the low saline part of the Baltic Sea. Biometric data show that P. minimum cells differ significantly in size between areas in the Baltic Sea.

  • 126. Hakonen, Aron
    et al.
    Anderson, Leif G.
    Engelbrektsson, Johan
    Hulth, Stefan
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    A potential tool for high-resolution monitoring of ocean acidification2013In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 786, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Current anthropogenic carbon dioxide emissions generate besides global warming unprecedented acidification rates of the oceans. Recent evidence indicates the possibility that ocean acidification and low oceanic pH may be a major reason for several mass extinctions in the past. However, a major bottleneck for research on ocean acidification is long-term monitoring and the collection of consistent high-resolution pH measurements. This study presents a low-power (<1 W) small sample volume (25 mu L) semiconductor based fluorescence method for real-time ship-board pH measurements at high temporal and spatial resolution (approximately 15 s and 100 m between samples). A 405 nm light emitting diode and the blue and green channels from a digital camera was used for swift detection of fluorescence from the pH sensitive dye 6,8-Dihydroxypyrene-1,3-disulfonic acid in real-time. Main principles were demonstrated by automated continuous measurements of pH in the surface water across the Baltic Sea and the Kattegat region with a large range in salinity (similar to 3-30) and temperature (similar to 0-25 degrees C). Ship-board precision of salinity and temperature adjusted pH measurements were estimated as low as 0.0001 pH units. (C) 2013 Elsevier B. V. All rights reserved.

  • 127. Hall, Per O. J.
    et al.
    Almroth-Rosell, Elin
    SMHI, Research Department, Oceanography.
    Bonaglia, Stefano
    Dale, Andrew W.
    Hylén, Astrid
    Kononets, Mikhail
    Nilsson, Madeleine
    Sommer, Stefan
    van de Velde, Sebastiaan
    Viktorsson, Lena
    SMHI, Core Services.
    Influence of Natural Oxygenation of Baltic Proper Deep Water on Benthic Recycling and Removal of Phosphorus, Nitrogen, Silicon and Carbon2017In: Frontiers in Marine Science, ISSN 2296-7745, Vol. 4, no 27Article in journal (Refereed)
  • 128.
    Hansson, Lars J.
    et al.
    SMHI, Research Department, Oceanography.
    Hansson, Lars Johan
    SMHI.
    Craig, Sean F.
    Hughes, Roger N.
    Bishop, John D. D.
    Microscale genetic differentiation in a sessile invertebrate with cloned larvae: investigating the role of polyembryony2007In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 153, no 1, p. 71-82Article in journal (Refereed)
    Abstract [en]

    Microscale genetic differentiation of sessile organisms can arise from restricted dispersal of sexual propagules, leading to isolation by distance, or from localised cloning. Cyclostome bryozoans offer a possible combination of both: the localised transfer of spermatozoa between mates with limited dispersal of the resulting larvae, in association with the splitting of each sexually produced embryo into many clonal copies (polyembryony). We spatially sampled 157 colonies of Crisia denticulata from subtidal rock overhangs from one shore in Devon, England at a geographic scale of ca. 0.05 to 130 m plus a further 21 colonies from Pembrokeshire, Wales as an outgroup. Analysis of molecular variance (AMOVA) revealed that the majority (67%) of genetic variation was distributed among individuals within single rock overhangs, with only 16% of variation among different overhangs within each shore and 17% of variation between the ingroup and outgroup shores. Despite local genetic variation, pairwise genetic similarity analysed by spatial autocorrelation was greatest at the smallest inter-individual distance we tested (5 cm) and remained significant and positive across generally within-overhang comparisons (< 4 m). Spatial autocorrelation and AMOVA analyses both indicated that patches of C. denticulata located on different rock overhangs tended to be genetically distinct, with the switch from positive to negative autocorrelation, which is often considered to be the distance within which individuals reproduce with their close relatives or the radius of a patch, occurring at the 4-8 m distance class. Rerunning analyses with twenty data sets that only included one individual of each multilocus genotype (n = 97) or the single data set that contained just the unique genotypes (n = 67) revealed that the presence of repeat genotypes had an impact on genetic structuring (PhiPT values were reduced when shared genotypes were removed from the dataset) but that it was not great and only statistically evident at distances between individuals of 1-2 m. Comparisons to a further 20 randomisations of the data set that were performed irrespective of genotype (n = 97) suggested that this conclusion is not an artefact of reduced sample size. A resampling procedure using kinship coefficients, implemented by the software package GENCLONE gave broadly similar results but the greater statistical power allowed small but significant impacts of repeat genotypes on genetic structure to be also detected at 0.125-0.5 and 4-16 m. Although we predict that a proportion of the repeat multilocus genotypes are shared by chance, such generally within-overhang distances may represent a common distance of cloned larval dispersal. These results suggests that closely situated potential mates include a significant proportion of the available genetic diversity within a population, making it unlikely that, as previously hypothesised, the potential disadvantage of producing clonal broods through polyembryony is offset by genetic uniformity within the mating neighbourhood. We also report an error in the published primer note of Craig et al. (Mol Ecol Notes 1:281-282, 2001): loci Cd5 and Cd6 appear to be the same microsatellite.

  • 129.
    Hansson, Martin
    et al.
    SMHI, Core Services.
    Andersson, Lars
    SMHI, Core Services.
    Axe, Philip
    SMHI, Research Department, Oceanography.
    Areal Extent and Volume of Anoxia and Hypnoxia in the Baltic Sea, 1960-20112011Report (Other academic)
    Abstract [en]

    A climatology atlas of the oxygen situation in the deep water of the Baltic Sea from 1960 to 2011 has been created based on all available data from ICES. Additional data collected during the Baltic International Acoustic Survey (BIAS) have been added to the year 2011. For the autumn period, each profile in the data set was examined for the occurrence of hypoxia (oxygen deficiency) and anoxia (total absence of oxygen). The depths of the onset of hypoxia and anoxia were then interpolated between sampling stations producing two surfaces representing the depth at which hypoxic and anoxic conditions are found. The volume and area of hypoxia and anoxia have been calculated and the results have then been transformed to maps and diagrams to visualize the annual autumn oxygen situation during the analysed period. From the analysed oxygen data 1960-2011 a distinct regime shift has been identified in 1999. During the first regime, 1960 to 1999, hypoxia affected large areas and volumes while anoxic conditions affected only minor deep areas. After the regime shift in 1999 both the areal extent and volume of hypoxia and anoxia are elevated to levels never recorded before. The bottom areas of the Baltic Proper (including the Gulf of Finland and the Gulf of Riga) affected by anoxic conditions have increased from 5%, before the regime shift, to 15% after, i.e. by a factor of 3. The extent of hypoxia has increased from 22% to 28%, i.e. by a factor of ~1.3. Excluding the results from 2011, which are preliminary, the largest areal extent of anoxia, 18%, in the Baltic Proper was recorded in 2005 and the largest affected water volume, 10%, was recorded in 2001. The cause and ecosystem effects of the new behaviour of the Baltic Sea that has been recognized after the regime shift, with continuously extreme oxygen conditions, are still not fully understood. However, there are several likely contributory and concurrent causes to the recent development such as changes in winds, changes in frequency and characteristics of inflows, increased loading of organic matter to the deep water, altered vertical mixing and stratification, and changed freshwater runoff. Historically, the oxygen development in the deep water of the Baltic Sea has been investigated in detail and most of the processes involved, both physical and chemical, have been described. But the development during the 2000s is alarming and should be investigated thoroughly. The areal extent and volume of hypoxia have today probably reached the maximal possible extent due to the permanent stratification in the Baltic Proper. However, the extent and volume of anoxic conditions can still increase, which further can enhance the eutrophication of the Baltic Sea due to released phosphorus from sediments that previously have been oxygenated. Sammanfattning En klimatologisk atlas av syresituationen i Östersjöns djupvatten från 1960 till 2011 har skapats baserad på all tillgänglig data från ICES. Ytterligare data från Baltic International Acoustic Survey (BIAS) har inkluderats separat för 2011. Förekomsten av hypoxi (syrebrist) och anoxi (helt syrefria förhållanden) under höstperioden har undersökts i varje mätprofil. Djupet då hypoxi eller anoxi först påträffas i en profil har interpolerats mellan provtagningsstationer och kombinerats med en djupdatabas för beräkning av utbredning och volym av hypoxiska och anoxiska förhållanden. Resultaten har överförts till kartor och diagram för att visualisera syresituationen i Östersjöns djupvatten. Utifrån analyserade data från perioden 1960-2011 har ett distinkt regimskifte skett 1999. Under den första regimen, från 1960 till 1999, påverkade hypoxi stora områden och volymer, medan anoxi enbart påverkade mindre djupområden. Efter regimskiftet 1999 har andelen hypoxi och anoxi förhöjts till nivåer som aldrig tidigare observerats i Östersjöns djupvatten. Utbredningen av bottnar påverkade av anoxi har i medeltal ökat från 5% av Egentliga Östersjöns (inklusive Finska viken och Rigabukten) bottenarea till 15%, i och med regimskiftet, d.v.s. med en faktor 3. Utbredningen av hypoxi har också ökat från 22% till 28% d.v.s. med en faktor ~1.3. Den största utbredningen av anoxi, 18%, i Egentliga Östersjön observerades 2005 och den största påverkade vattenvolymen, 10%, noterades 2001. Utvecklingen i Östersjön med fortsatt extrema syreförhållanden efter regimskiftet och dess orsaker och konsekvenser för Östersjöns ekosystem är idag inte helt klarlagd. Det finns emellertid flera troliga orsaker som kan samverka såsom; förändrade vindförhållanden, förändrad frekvens och karaktäristik av inflöden, ökad belastning av organiskt material till djupvattnet, förändrad vertikal omblandning samt skiktning och ändrad tillrinning till Östersjön. Historiskt så har syreförhållanden i Östersjön undersökts i detalj och de flesta processer, både fysiska och kemiska finns beskrivna. Men utvecklingen under 2000-talet är alarmerande och måste noggrant undersökas. Utbredningen och volymen av hypoxi har idag (2011) antagligen nått den övre gränsen för vad som är fysiskt möjligt med den permanenta skiktning som finns i Östersjön. De anoxiska förhållandena kan dock fortsatt öka om den negativa utvecklingen fortsätter, vilket ytterligare kan förvärra övergödningsproblematiken i Östersjön då mer fosfor kan frigöras från bottnar som tidigare varit syresatta.

  • 130.
    Hansson, Martin
    et al.
    SMHI, Core Services.
    Andersson, Lars
    SMHI, Core Services.
    Axe, Philip
    SMHI, Research Department, Oceanography.
    Szaron, Jan
    SMHI.
    Oxygen Survey in the Baltic Sea 2012: Extent of Anoxia and Hypoxia, 1960-20122013Report (Other academic)
    Abstract [en]

    En klimatologisk atlas av syresituationen i Östersjöns djupvatten publicerades 2011 i SMHIs Report Oceanography No 42. Resultaten för 2011 var preliminära och har i denna rapport uppdaterats då ny data har rapporterats till ICES. Resultaten för 2012 är preliminära och är baserade på syredata insamlade under Baltic International Acoustic Survey (BIAS) med bidrag från Sverige, Polen, Estland och Finland. Data från SMHIs egna ordinarie expeditioner har också inkluderats.Förekomsten av hypoxi (syrebrist) och anoxi (helt syrefria förhållanden) under höstperioden, augusti till oktober, har undersökts i varje mätprofil. Djupet då hypoxi eller anoxi först påträffas i en profil har interpolerats mellan provtagningsstationer och kombinerats med en djupdatabas för beräkning av utbredning och volym av hypoxiska och anoxiska förhållanden. Resultaten har överförts till kartor och diagram för att visualisera syresituationen i Östersjöns djupvatten.Resultaten för 2011 och de preliminära resultaten för 2012 visar att de extrema syreförhållanden som observerat i Egentliga Östersjön efter regimskiftet 1999 fortsätter. Andelen områden påverkade av hypoxi och anoxi fortsätter att vara förhöjda till nivåer som aldrig tidigare observerats i Östersjöns djupvatten.

  • 131. Hansson, Martin
    et al.
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    The Baltic Algae Watch System - a remote sensing application for monitoring cyanobacterial blooms in the Baltic Sea2007In: Journal of Applied Remote Sensing, ISSN 1931-3195, E-ISSN 1931-3195, Vol. 1, article id 011507Article in journal (Refereed)
    Abstract [en]

    Nowcasting of harmful algal blooms is important both for the public and for environmental management purposes. In the Baltic Sea summer blooms of nitrogen-fixing cyanobacteria are regular phenomena but the past years intense and widespread blooms have caused major environmental concern due to its nuisance, increased nitrogen input and toxicity. The Swedish Meteorological and Hydrological Institute have developed a monitoring application that use satellite data to detect blooms and that assembles essential sources of information at one website. A supervised classifications algorithm has been applied to NOAA-AVHRR data during 1997-2006 and the dataset collected has been evaluated and analyzed. Subsequently, definitions of normalized bloom duration, extent and intensity have been developed to enable comparison between different years. Results suggest that the most intense blooms during 1997-2006 were recorded in 2006, while both 2005 and 2006 had the longest duration. The largest extent was noted in 1998. The experience from the 10 years of monitoring has shown that the combination of satellite imagery, observations, forecasts and tools assembled at one website, is a powerful nowcasting tool for monitoring and prediction of cyanobacterial blooms.

  • 132. Hense, Inga
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Sonntag, Sebastian
    Projected climate change impact on Baltic Sea cyanobacteria Climate change impact on cyanobacteria2013In: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 119, no 2, p. 391-406Article in journal (Refereed)
    Abstract [en]

    Compared to other phytoplankton groups, nitrogen-fixing cyanobacteria generally prefer high water temperatures for growth and are therefore expected to benefit from global warming. We use a coupled biological-physical model with an advanced cyanobacteria life cycle model to compare the abundance of cyanobacteria in the Baltic Sea during two different time periods (1969-1998; 2069-2098). For the latter, we find prolonged growth and a more than twofold increase in the climatologically (30 years) averaged cyanobacteria biomass and nitrogen fixation. Additional sensitivity experiments indicate that the biological-physical feedback mechanism through light absorption becomes more important with global warming. In general, we find a nonlinear response of cyanobacteria to changes in the atmospheric forcing fields as a result of life-cycle related feedback mechanisms. Overall, the sensitivity of the cyanobacteria-driven system suggests that biological-physical and life-cycle related feedback mechanisms are important and must therefore be included in future projection studies.

  • 133.
    Hieronymus, Jenny
    et al.
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Hieronymus, Magnus
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Saraiva, Sofia
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    Causes of simulated long-term changes in phytoplankton biomass in the Baltic proper: a wavelet analysis2018In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, no 16, p. 5113-5129Article in journal (Refereed)
  • 134.
    Hieronymus, Magnus
    SMHI, Research Department, Oceanography.
    An update on the thermosteric sea level rise commitment to global warming2019In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 14, no 5, article id 054018Article in journal (Refereed)
  • 135.
    Hieronymus, Magnus
    et al.
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    The effects of mean sea level rise and strengthened winds on extreme sea levels in the Baltic Sea2018In: Theoretical and Applied Mechanics Letters, ISSN 2095-0349, Vol. 8, no 6, p. 366-371Article in journal (Refereed)
  • 136.
    Hieronymus, Magnus
    et al.
    SMHI, Research Department, Oceanography.
    Hieronymus, Jenny
    SMHI, Research Department, Oceanography.
    Arneborg, Lars
    SMHI, Research Department, Oceanography.
    Sea level modelling in the Baltic and the North Sea: The respective role of different parts of the forcing2017In: Ocean Modelling, ISSN 1463-5003, E-ISSN 1463-5011, Vol. 118, p. 59-72Article in journal (Refereed)
  • 137.
    Hieronymus, Magnus
    et al.
    SMHI, Research Department, Oceanography.
    Hieronymus, Jenny
    SMHI, Research Department, Oceanography.
    Hieronymus, Fredrik
    On the Application of Machine Learning Techniques to Regression Problems in Sea Level Studies2019In: Journal of Atmospheric and Oceanic Technology, ISSN 0739-0572, E-ISSN 1520-0426, Vol. 36, no 9, p. 1889-1902Article in journal (Refereed)
    Abstract [en]

    Long sea level records with high temporal resolution are of paramount importance for future coastal protection and adaptation plans. Here we discuss the application of machine learning techniques to some regression problems commonly encountered when analyzing such time series. The performance of artificial neural networks is compared with that of multiple linear regression models on sea level data from the Swedish coast. The neural networks are found to be superior when local sea level forcing is used together with remote sea level forcing and meteorological forcing, whereas the linear models and the neural networks show similar performance when local sea level forcing is excluded. The overall performance of the machine learning algorithms is good, often surpassing that of the much more computationally costly numerical ocean models used at our institute.

  • 138.
    Hieronymus, Magnus
    et al.
    SMHI, Research Department, Oceanography.
    Nycander, Jonas
    Nilsson, Johan
    Doos, Kristofer
    Hallberg, Robert
    Oceanic Overturning and Heat Transport: The Role of Background Diffusivity2019In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 32, no 3, p. 701-716Article in journal (Refereed)
  • 139. Ho-Hagemann, Ha Thi Minh
    et al.
    Groger, Matthias
    SMHI, Research Department, Oceanography.
    Rockel, Burkhardt
    Zahn, Matthias
    Geyer, Beate
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Effects of air-sea coupling over the North Sea and the Baltic Sea on simulated summer precipitation over Central Europe2017In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 49, no 11-12, p. 3851-3876Article in journal (Refereed)
  • 140. Holopainen, Reetta
    et al.
    Lehtiniemi, Maiju
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Albertsson, Jan
    Gorokhova, Elena
    Kotta, Jonne
    Viitasalo, Markku
    Impacts of changing climate on the non-indigenous invertebrates in the northern Baltic Sea by end of the twenty-first century2016In: Biological Invasions, ISSN 1387-3547, E-ISSN 1573-1464, Vol. 18, no 10, p. 3015-3032Article in journal (Refereed)
  • 141. Hood, Lon
    et al.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Spangehl, Thomas
    Bal, Sourabh
    Cubasch, Ulrich
    The Surface Climate Response to 11-Yr Solar Forcing during Northern Winter: Observational Analyses and Comparisons with GCM Simulations2013In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 26, no 19, p. 7489-7506Article in journal (Refereed)
    Abstract [en]

    The surface climate response to 11-yr solar forcing during northern winter is first reestimated by applying a multiple linear regression (MLR) statistical model to Hadley Centre sea level pressure (SLP) and sea surface temperature (SST) data over the 1880-2009 period. In addition to a significant positive SLP response in the North Pacific found in previous studies, a positive SST response is obtained across the midlatitude North Pacific. Negative but insignificant SLP responses are obtained in the Arctic. The derived SLP response at zero lag therefore resembles a positive phase of the Arctic Oscillation (AO). Evaluation of the SLP and SST responses as a function of phase lag indicates that the response evolves from a negative AO-like mode a few years before solar maximum to a positive AO-like mode at and following solar maximum. For comparison, a similar MLR analysis is applied to model SLP and SST data from a series of simulations using an atmosphere-ocean general circulation model with a well-resolved stratosphere. The simulations differed only in the assumed solar cycle variation of stratospheric ozone. It is found that the simulation that assumed an ozone variation estimated from satellite data produces solar SLP and SST responses that are most consistent with the observational results, especially during a selected centennial period. In particular, a positive SLP response anomaly is obtained in the northeastern Pacific and a corresponding positive SST response anomaly extends across the midlatitude North Pacific. The model response versus phase lag also evolves from a mainly negative AO-like response before solar maximum to a mainly positive AO response at and following solar maximum.

  • 142.
    Hordoir, Robinson
    et al.
    SMHI, Research Department, Oceanography.
    An, B.W.
    SMHI.
    Haapala, J.
    SMHI.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    A 3D Ocean Modelling Configuration for Baltic & North Sea Exchange Analysis: BaltiX V 1.12013Report (Other academic)
    Abstract [en]

    There is a need for having a reliable numerical representation of the exchanges between the Baltic Sea and the North Sea from many points of view. First, the North Sea is the salt provider of the BalticSea, but also the oxygen provider of the lowermost layers of the Baltic Sea. This means that any numerical analysis which has for goal to study the long term changes in this exchange can not rely on a model of the Baltic Sea that has an open boundary condition at the entrance of the Baltic Sea (i.e.: the Kattegat area). In order to represent the long term changes in the exchanges between the NorthSea and the Baltic Sea, one needs to consider the coupling between these two basins which have a very different dynamical behaviour which means one needs to consider them as a whole. This meansthat any regional model should have its open boundary condition further away from the entrance of the Baltic Sea, that is in a place that is remote enough to allow a buffer large enough in the North Sea,so that the SSH variability at the entrance of the Baltic Sea is well represented [7].Second, the Baltic Sea outflow has a great influence on the Norwegian Coastal Current (NCC hereafter) which is also interesting to study, and which can only be well represented if the wind effect over the Baltic Sea is taken into account [9].Many models were successfully applied to the Baltic Sea or/and to the North Sea/Baltic Sea area. On can cite the Rossby Centre Ocean model RCO [15], which successfully represents the thermo-haline as well as the ice structures and variability of the Baltic Sea. One can also cite HIROMB [6], which is a North & Baltic Seas numerical representation used in operational oceanography.However, all these modelling structures lack in at least one of the following points :They include only the Baltic Sea area, which makes impossible the study of the exchanges withthe North Sea.- They were mostly used for operational purpose, and do not have stability properties in terms ofBaltic salt content which does not make them suitable for long term studies.- They do not follow anymore the framework of a community model, and therefore do not benefit of the recent scientific or technical developments implemented in most ocean modelling platform.- A Baltic & North Sea setup is also necessary for long term coupled simulations.There was therefore a need to build a new Baltic & North Sea configuration, based on a community modelling framework, and designed to follow this framework eventually.BaltiX is a Baltic & North Sea configuration based on the NEMO [14] ocean engine. Its development was started in 2011 at SMHI (Swedish Meteorological & Hydrological Institute, Norrköping, Sweden). It follows closely the development of the NEMO ocean engine, and BaltiX is updated each time an update is done in it.In the present report, Section 2 describes the configuration and explains the choices that have been made to build it. Based on a simulation done for the period 1961-2007, we then present several results. Section 3 presents a barotropic analysis of the results provided by the configuration, and Section 4 presents results in terms of salinity and temperature variability. Section 5 has been specifically written to present the sea-ice model coupled to BaltiX and its effects in terms of sea-ice variability. A last part provides a short conclusion to the present report.

  • 143.
    Hordoir, Robinson
    et al.
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Fransner, Filippa
    Groger, Matthias
    SMHI, Research Department, Oceanography.
    Liu, Ye
    SMHI, Research Department, Oceanography.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Ljungemyr, Patrik
    SMHI, Core Services.
    Nygren, Petter
    SMHI, Core Services.
    Falahat, Saeed
    SMHI, Core Services.
    Nord, Adam
    SMHI, Core Services.
    Jönsson, Anette
    SMHI, Core Services.
    Lake, Irene
    SMHI, Core Services. SMHI, Research Department, Climate research - Rossby Centre.
    Doos, Kristofer
    Hieronymus, Magnus
    SMHI, Research Department, Oceanography.
    Dietze, Heiner
    Loeptien, Ulrike
    Kuznetsov, Ivan
    Westerlund, Antti
    Tuomi, Laura
    Haapala, Jari
    Nemo-Nordic 1.0: a NEMO-based ocean model for the Baltic and North seas - research and operational applications2019In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 12, no 1, p. 363-386Article in journal (Refereed)
  • 144.
    Hordoir, Robinson
    et al.
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Löptien, Ulrike
    SMHI, Research Department, Oceanography.
    Dietze, Heiner
    Kuznetsov, Ivan
    SMHI, Research Department, Oceanography.
    Influence of sea level rise on the dynamics of salt inflows in the Baltic Sea2015In: Journal of Geophysical Research - Oceans, ISSN 2169-9275, E-ISSN 2169-9291, Vol. 120, no 10, p. 6653-6668Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea is a marginal sea, located in a highly industrialized region in Central Northern Europe. Saltwater inflows from the North Sea and associated ventilation of the deep exert crucial control on the entire Baltic Sea ecosystem. This study explores the impact of anticipated sea level changes on the dynamics of those inflows. We use a numerical oceanic general circulation model covering both the Baltic and the North Sea. The model successfully retraces the essential ventilation dynamics throughout the period 1961-2007. A suite of idealized experiments suggests that rising sea level is associated with intensified ventilation as saltwater inflows become stronger, longer, and more frequent. Expressed quantitatively as a salinity increase in the deep central Baltic Sea, we find that a sea level rise of 1 m triggers a saltening of more than 1 PSU. This substantial increase in ventilation is the consequence of the increasing cross section in the Danish Straits amplified by a reduction of vertical mixing.

  • 145.
    Hordoir, Robinson
    et al.
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Basu, Chandan
    Dietze, Heiner
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Freshwater outflow of the Baltic Sea and transport in the Norwegian current: A statistical correlation analysis based on a numerical experiment2013In: Continental Shelf Research, ISSN 0278-4343, E-ISSN 1873-6955, Vol. 64, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Based on the results of a numerical ocean model, we investigate statistical correlations between wind forcing, surface salinity and freshwater transport out of the Baltic Sea on one hand, and Norwegian coastal current freshwater transport on the other hand. These correlations can be explained in terms of physics and reveal how the two freshwater transports are linked with wind forcing, although this information proves to be non-sufficient when it comes to the dynamics of the Norwegian coastal current. Based on statistical correlations, the Baltic Sea freshwater transport signal is reconstructed and shows a good correlation but a poor variability when compared with the measured signal, at least when data filtered on a two-daily time scale is used. A better variability coherence is reached when data filtered on a weekly or monthly time scale is used. In the latest case, a high degree of precision is reached for the reconstructed signal. Using the same kind of methods for the case of the Norwegian coastal current, the negative peaks of the freshwater transport signal can be reconstructed based on wind data only, but the positive peaks are under-represented although some of them exist mostly because the meridional wind forcing along the Norwegian coast is taken into account. Adding Norwegian coastal salinity data helps improving the reconstruction of the positive peaks, but a major improvement is reached when adding non-linear terms in the statistical reconstruction. All coefficients used to re-construct both freshwater transport signals are provided for use in European Shelf or climate modeling configurations. (c) 2013 Elsevier Ltd. All rights reserved.

  • 146.
    Hordoir, Robinson
    et al.
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Sensitivity of the overturning circulation of the Baltic Sea to climate change, a numerical experiment2018In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 50, no 3-4, p. 1425-1437Article in journal (Refereed)
  • 147.
    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.

  • 148.
    Hordoir, Robinson
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Freshwater fluxes in the Baltic Sea: A model study2010In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, article id C08028Article in journal (Refereed)
    Abstract [en]

    The dynamics of "juvenile" freshwater, which is released during spring into the Baltic proper, is studied using a numerical three-dimensional circulation model. Two methods are used. First, freshwater heights are calculated using simulated salinity fields, and their seasonal variability is analyzed. When compared to climatological observations, the model represents the seasonal variability of freshwater heights well. However, the method does not allow a proper study of the dynamics of juvenile freshwater fluxes. Consequently, a second method is used where a passive tracer, which marks freshwater, is utilized. This method provides a better description of the seasonal spreading of juvenile freshwater in the Baltic proper, although further investigations are still necessary to trace juvenile freshwater. The results from this second method show that juvenile freshwater does not reach the center of the Baltic proper before late summer. During one season, only a small amount of juvenile freshwater may reach the entrance of the Baltic Sea. The increased vertical stratification generated by the arrival of juvenile freshwater and the subsequent baroclinic adjustment may trigger the onset of the spring bloom in accordance to earlier suggestions. Further, the seasonal cycle and inter-annual variability of the freshwater outflow from the Baltic Sea are studied. Seasonal changes of the freshwater outflow are closely connected with that of the zonal wind, although the annual mean outflow is given by the total runoff into the Baltic Sea. Thus, the inter-annual variability of the seasonal freshwater outflow maximum is highly correlated with the North Atlantic Oscillation.

  • 149. Hu, Yue O. O.
    et al.
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    Charvet, Sophie
    Andersson, Anders F.
    Diversity of Pico- to Mesoplankton along the 2000 km Salinity Gradient of the Baltic Sea2016In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 7, article id 679Article in journal (Refereed)
  • 150. Humborg, C
    et al.
    Smedberg, E
    Blomqvist, S
    Morth, C M
    Brink, J
    Rahm, Lars
    SMHI, Research Department, Oceanography.
    Danielsson, A
    Sahlberg, Jörgen
    SMHI, Professional Services. SMHI, Research Department, Oceanography.
    Nutrient variations in boreal and subarctic Swedish rivers: Landscape control of land-sea fluxes2004In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 49, no 5, p. 1871-1883Article in journal (Refereed)
    Abstract [en]

    We examined the hypothesis that the extent of vegetation cover governs the fluxes of nutrients from boreal and subarctic river catchments to the sea. Fluxes of total organic carbon (TOC) and dissolved inorganic nitrogen, phosphorus, and dissolved silicate (DIN, DIP, and DSi, respectively) are described from 19 river catchments and subcatchments (ranging in size from 34 to 40,000 km(2)) in northern Sweden with a detailed analysis of the rivers Lulealven and Kalixalven. Fluxes of TOC, DIP, and DSi increase by an order of magnitude with increasing proportion of forest and wetland area, whereas DIN did not follow this pattern but remained constantly low. Principal component analysis on landscape variables showed the importance of almost all land cover and soil type variables associated with vegetation, periglacial environment, soil and bedrock with slow weathering rates, boundary of upper tree line, and percentage of lake area. A cluster analysis of the principal components showed that the river systems could be separated into mountainous headwaters and forest and wetland catchments. This clustering was also valid in relation to river chemistry (TOC, DIP, and DSi) and was confirmed with a redundancy analysis, including river chemistry and principal components as environmental variables. The first axis explains 89% of the variance in river chemistry and almost 100% of the variance in the relation between river chemistry and landscape variables. These results suggest that vegetation change during interglacial periods is likely to have had a major effect on inputs of TOC, DIP, and DSi into the past ocean.

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