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  • 201.
    Löptien, Ulrike
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Simulated distribution of colored dissolved organic matter in the Baltic Sea2011Report (Other academic)
    Abstract [en]

    The Baltic Sea is optically a multi-componental water and has exceedingly high levels of colored dissolved organic matter (CDOM, also referred as yellow matter, gilvin or gelbstoff). CDOM is a complex mixture of chemical bonds originating from the decay of photosynthetically produced organic matter. It influences the aquatic light field substantially. A quantitative description of the dynamics and variability is often required to predict accurately light penetration and hereafter e.g. primary production. The present study is a first attempt to include CDOM into a Baltic Sea model. The model integrations are based on a fixed concentration in the 30 major rivers. In the absence of comprehensive measurements, a river inflow proportional to total organic carbon is assumed. Since origin and fate are still a matter of discussion, we test various decay rates of CDOM and compare the results with satellite observations. Best results are obtained when assuming a light dependent decay, compared to a temperature or time dependent decay. Treating CDOM as a conservative tracer does not lead to satisfactory results. Sammanfattning

  • 202.
    Löptien, Ulrike
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    The influence of increasing water turbidity on the sea surface temperature in the Baltic Sea: A model sensitivity study2011In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 88, no 2, p. 323-331Article in journal (Refereed)
    Abstract [en]

    The aim of the present study is to investigate the influence of enhanced absorption of sunlight at the sea surface due to increasing water turbidity and its effect on the sea surface temperatures (SST) in the Baltic Sea. The major question behind our investigations is, whether this effect needs to be included in Baltic Sea circulation models or can be neglected. Our investigations cover both, mean state and SST trends during the recent decades. To quantify the impact of water turbidity on the mean state different sensitivity ocean hind-cast experiments are performed. The state-of-the art ocean model RCO (Rossby Centre Ocean model) is used to simulate the period from 1962 to 2007. In the first simulation, a spatially and temporally constant value for the attenuation depth is used, while in the second experiment a climatological monthly mean, spatially varying attenuation coefficient is derived from satellite observations of the diffuse attenuation coefficient at 490 nm. The inclusion of a spatially varying light attenuation leads to significant SST changes during summer. Maximum values of + 0.5 K are reached in the Gulf of Finland and close to the eastern coasts, when compared to a fixed attenuation of visible light of 0.2 m(-1). The temperature anomalies basically match the pattern of increased light attenuation with strongest effects in shallow waters. Secondary effects due to changes in the current system are of minor importance. Similar results are obtained when considering trends. In the absence of long-term basin wide observations of attenuation coefficients, some idealizations have to be applied when investigating the possible influence of long-term changes in water turbidity on the SST. Two additional sensitivity experiments are based on a combination of long-term Secchi depth station observations and the present day pattern of water turbidity, as observed by satellite. We show the potential of increased water turbidity to affect the summer SST trends in the Baltic Sea significantly, while the estimated effect is apparently too small to explain the overall extreme summer trends observed in the Baltic Sea. (C) 2011 Elsevier B.V. All rights reserved.

  • 203. MACDONALD, RW
    et al.
    PATON, DW
    CARMACK, EC
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    THE FRESH-WATER BUDGET AND UNDER-ICE SPREADING OF MACKENZIE RIVER WATER IN THE CANADIAN BEAUFORT SEA BASED ON SALINITY AND O-18/O-16 MEASUREMENTS IN WATER AND ICE1995In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 100, no C1, p. 895-919Article in journal (Refereed)
    Abstract [en]

    Observations of salinity and oxygen isotope composition (delta(18)O) were made for the Beaufort shelf-Mackenzie estuary waters in September 1990, just prior to ice formation, and for both the water column and ice in April-May 1991, at the end of winter. These measurements are used to determine the apportioning of fresh water in the estuary between its two main sources, runoff and sea ice melt. Changes in disposition of water between seasons and amounts frozen into the growing ice sheet are also derived. Two domains are considered in order to construct a freshwater budget for the Mackenzie shelf, the nearshore within which landfast ice grows in winter and the outer shelf. Most of the winter inflow from the Mackenzie River appears to remain impounded as liquid under the ice within the landfast zone at the end of winter, and about 15% of it is incorporated into the landfast ice. Oxygen isotopes (delta(18)O) in ice cores collected from across the shelf record the progress beneath the ice of new Mackenzie inflow as it invades the nearshore throughout winter. Rates of spreading are about 0.2 cm s(-1) away from the coast and 1.3 cm s(-1) along the coast. As this inflow spreads across the shelf, it progressively shuts off convection driven by brine production at locations within the landfast ice. Salinity and delta(18)O in the offshore water column suggest that about 3 m of sea ice was for:med in the outer shelf domain. Since both brine and newly formed sea ice can be advected off the shelf, a complete budget for brine or sea ice production cannot be established without first measuring the advection of one of these two components.

  • 204. MacIntyre, Sally
    et al.
    Crowe, Adam. T.
    Cortes, Alicia
    Arneborg, Lars
    SMHI, Research Department, Oceanography.
    Turbulence in a small arctic pond2018In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 63, no 6, p. 2337-2358Article in journal (Refereed)
  • 205. MacKenzie, Brian R.
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Lindegren, Martin
    Neuenfeldt, Stefan
    Eero, Margit
    Blenckner, Thorsten
    Tomczak, Maciej T.
    Niiranen, Susa
    Impact of Climate Change on Fish Population Dynamics in the Baltic Sea: A Dynamical Downscaling Investigation2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 626-636Article in journal (Refereed)
    Abstract [en]

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

  • 206.
    Marmefelt, Eleonor
    et al.
    SMHI, Professional Services.
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    Erichsen, Anders Christan
    Sehested Hansen, Ian
    Institute of Marine Research, Bergen, Norway..
    Development of an Ecological Model System for the Kattegat and the Southern Baltic: Final Report to the Nordic Councils of Ministers2000Report (Other academic)
  • 207.
    Marmefelt, Eleonor
    et al.
    SMHI, Professional Services.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    DEEP-WATER PROPERTIES IN THE GULF OF BOTHNIA1993In: Continental Shelf Research, ISSN 0278-4343, E-ISSN 1873-6955, Vol. 13, no 2-3, p. 169-187Article in journal (Refereed)
    Abstract [en]

    The northern extension of the Baltic Sea, the Gulf of Bothnia, is a weakly stratified sea. One would therefore expect that the deep water of the Gulf is easily renewed through deep thermal convection, or even through deep haline convection, as the Gulf is more or less covered with ice every winter. However, the present study shows, through analysis of historical temperature, salinity and density data, that the deep water in the Gulf of Bothnia is mainly renewed by major inflows of Baltic Proper surface water. The penetrating water forms a dense bottom current in the Gulf. In the southern part of the Gulf, the Bothnian Sea, the volume flow of the bottom current is found to increase by 10%. It is therefore not likely that the bottom current properties are changed to any appreciable extent. The bottom current properties in the Bothnian Bay, on the other hand, are highly affected, as the volume flow is estimated to increase by 150% in this basin.

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

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

  • 209.
    Mattsson, Johan
    SMHI, Research Department, Oceanography.
    Analysis of the exchange of salt between the Baltic and the Kattegat through the Oresund using a three-layer model1996In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 101, no C7, p. 16571-16584Article in journal (Refereed)
    Abstract [en]

    The shallowness of the Oresund prevents a continuous inflow of saline Kattegat water to the Baltic. Instead, the salt is exchanged largely by fluctuating barotropic transports. Buffer effects and temporal storage of low-salinity Baltic surface water complicate the exchange. The analysis of salt exchange through the Oresund requires use of a model of the stratification and baroclinically modified exchange processes. In this paper a three-layer model of the Oresund, forced by the exchange with the Kattegat and the Baltic, is formulated and calibrated. Frontal dynamics, necessary to explain the retreat of the uppermost layer, are included. The model is calibrated using genetic algorithms, which provide an efficient and robust optimization method for this kind of model. An analysis of the exchange in view of the model results is presented. The paper also gives estimates of typical mean quantities. For the analyzed period of 11 years (1977-1987) the mean salt outflow rate from the Baltic during outflows is 311,000 kg s(-1) and the mean salt inflow rate to the Baltic during inflows is 500,000 kg s(-1). The net salt outflow from the Baltic is estimated to 19,000 kg s(-1). The mean frontal speed is estimated at 0.25 m s(-1) and the typical required length of an inflow event for high-salinity Kattegat water to reach the Baltic is estimated at 4 days. Further results are also given. In addition, the baroclinic dynamics of the Oresund are discussed.

  • 210.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Baltic Sea climate in the late twenty-first century: a dynamical donwscaling approach using two global models and two emission scenarios2006In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 1, no 27, p. 39-68Article in journal (Refereed)
  • 211.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Baltic Sea climate in the late twenty-first century: a dynamical downscaling approach using two global models and two emission scenarios2006In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 27, no 1, p. 39-68Article in journal (Refereed)
    Abstract [en]

    A regional ocean circulation model was used to project Baltic Sea climate at the end of the twenty-first century. A set of four scenario simulations was performed utilizing two global models and two forcing scenarios. To reduce model biases and to spin up future salinity the so-called Delta-change approach was applied. Using a regional coupled atmosphere-ocean model 30-year climatological monthly mean changes of atmospheric surface data and river discharge into the Baltic Sea were calculated from previously conducted time slice experiments. These changes were added to reconstructed atmospheric surface fields and runoff for the period 1903-1998. The total freshwater supply (runoff and net precipitation) is projected to increase between 0 and 21%. Due to increased westerlies in winter the annual mean wind speed will be between 2 and 13% larger compared to present climate. Both changes will cause a reduction of the average salinity of the Baltic Sea between 8 and 50%. Although salinity in the entire Baltic might be significantly lower at the end of the twenty-first century, deep water ventilation will very likely only slightly change. The largest change is projected for the secondary maximum of sea water age within the halocline. Further, the average temperature will increase between 1.9 and 3.2 degrees C. The temperature response to atmospheric changes lags several months. Future annual maximum sea ice extent will decrease between 46 and 77% in accordance to earlier studies. However, in contrast to earlier results in the warmest scenario simulation one ice-free winter out of 96 seasons was found. Although wind speed changes are uniform, extreme sea levels may increase more than the mean sea level. In two out of four projections significant changes of 100-year surge heights were found.

  • 212.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    First results of multi-year simulations using a 3D Baltic Sea model1999Report (Other academic)
  • 213.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Modeling the age of Baltic Seawater masses: Quantification and steady state sensitivity experiments2005In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 110, no C2, article id C02006Article in journal (Refereed)
    Abstract [en]

    [1] Ages of Baltic Seawater masses for the period 1903 - 1998 were quantified using a three-dimensional (3-D) coupled ice-ocean model. Therefore an additional Eulerian tracer for the age of seawater was embedded. The age is the time elapsed since a water particle left the sea surface. Median ages of the bottom water between 1 year in the Bornholm Basin and 7 years in the northwestern Gotland Basin were found. During 1903 - 1998 the oldest bottom water of about 11 years appeared at Landsort Deep. In the halocline of the deeper basins a secondary age maximum was calculated. In the eastern Gotland Basin 3 stagnation periods (in the 1920/1930s, 1950/1960s, and 1980/1990s) with ages exceeding 8 years were found. Further, the sensitivities of modeled salinity and age on freshwater supply, wind speed, and amplitude of the sea level in Kattegat were investigated. In steady state the average salinity of the Baltic is most sensitive to perturbations of freshwater inflow. Increased freshwater inflow and wind speed result both in decreased salinity whereas increased amplitude of the Kattegat sea level results in increased salinity. The average age is most sensitive to perturbations of the wind speed. Especially, decreased wind speed causes significantly increased age of the deep water. On the other hand, the impact of changing freshwater or sea level in Kattegat on the average age is comparatively small, suggesting invariance of stability and ventilation in steady state approximately. A simple conceptual model for the Baltic deep water ventilation was applied to explain the 3-D model results.

  • 214.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Modeling the pathways and ages of inflowing salt- and freshwater in the Baltic Sea2007In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 74, no 4, p. 610-627Article in journal (Refereed)
    Abstract [en]

    A three-dimensional, eddy-permitting ocean circulation model with implemented bottom boundary layer model and flux-corrected transport scheme is used to calculate the pathways and ages of various water masses in the Baltic Sea. The agreement between simulated and observed temperature and salinity profiles of the period 1980-2004 is satisfactory. Especially the renewal of the deep water in the Baltic proper by gravity-driven dense bottom flows is better simulated than in previous versions of the model. Based upon these model results details of the mean circulation are analyzed. For instance, it is found that after the major Baltic inflow in January 2003 saline water passing the Slupsk Furrow flows directly towards northeast along the eastern slope of the Hoburg Channel. However, after the baroclinic summer inflow in August/September 2002 the deep water flow spreads along the southwestern slope of the Gdansk Basin. Further, the model results show that the patterns of mean vertical advective fluxes across the halocline that close the large-scale vertical circulation are rather patchy. Mainly within distinct areas are particles of the saline inflow water advected vertically from the deep water into the surface layer. To analyze the time scales of the circulation mean ages of various water masses are calculated. It is found that at the sea surface of the Bornholm Basin, Gotland Basin, Bothnian Sea, and Bothnian Bay the mean ages associated to inflowing water from Kattegat amount to 26-30, 28-34, 34-38, and 38-42 years, respectively. Largest mean sea surface ages of more than 30 years associated to the freshwater of the rivers are found in the central Gotland Basin and Belt Sea. At the bottom the mean ages are largest in the western Gotland Basin and amount to more than 36 years. In the Baltic proper vertical gradients of ages associated to the freshwater inflow are smaller than in the case of inflowing saltwater from Kattegat indicating an efficient recirculation of freshwater in the Baltic Sea. (C) 2007 Elsevier Ltd. All rights reserved.

  • 215.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    On the parameterization of mixing in three-dimensional Baltic Sea models2001In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 106, no C12, p. 30997-31016Article in journal (Refereed)
    Abstract [en]

    As mixing plays a dominant role for the physics of an estuary like the Baltic Sea (seasonal heat storage, mixing in channels, deepwater mixing), different mixing parameterizations for use in three-dimensional (3-D) Baltic Sea models are discussed. Within the Swedish regional climate modeling program, SWECLIM, a 3-D coupled ice-ocean model for the Baltic Sea has been coupled with an improved version of the two-equation k-epsilon turbulence model using a corrected dissipation term, flux boundary conditions to include the effect of a turbulence enhanced layer due to breaking surface gravity waves, and a parameterization for breaking internal waves. Results of multiyear simulations are compared with observations. The seasonal thermocline (the main focus of this paper) is simulated satisfactory. During the stagnation period between 1983 and 1993, simulated salinity in the lower layer of the Baltic Sea decreases as observed. Unsolved problems of the k-epsilon model are discussed. To replace the controversial equation for dissipation, the performance of a hierarchy of k models has been tested and compared with the k-epsilon model. In addition, it is shown that the results of the 1-D turbulence submodel depend very much on the dimensionality of the hydrodynamic model. Using the same turbulence parameterization, vertical velocity shear and density gradients are simulated differently in 1-D column models compared to 3-D ocean circulation models. Finally, the impact of two mixing parameterizations on Baltic Sea climate is discussed.

  • 216.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Projected Change-Marine Physics2015Chapter in book (Other academic)
    Abstract [en]

    This chapter assesses recent results of changes in water temperature, salinity, sea ice, storm surges and wind waves during the twenty-first century in scenario simulations for the Baltic Sea. There have been several improvements since the first Baltic Sea assessment of climate change: the number of relevant scenario simulations has increased, ensembles of transient simulations with improved models based upon the scenarios and global models of IPCC's Fourth Assessment Report (AR4) have been analysed, and changes in biogeochemical cycles are now considered. The scenario simulations project that water temperatures will increase in the future, with the greatest changes in the northern Baltic Sea during summer. In agreement with earlier studies, sea-ice cover is projected to decrease drastically. Salinity is projected to decrease due to increased river run-off, whereas the impact of wind changes on salinity is negligible because the latter is relatively small. However, uncertainty in salinity projections is large owing to considerable bias in the simulated water balance. According to one study, salt transport into the Baltic Sea is unchanged. Sea-level rise has greater potential to increase surge levels in the Baltic Sea than increased wind speed, and changes in wind waves are projected to be small.

  • 217.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Regional ocean climate simulations with a 3D ice-ocean model for the Baltic Sea. Part 1: model experiments and results for temperature and salinity2002In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 19, no 3-4, p. 237-253Article in journal (Refereed)
    Abstract [en]

    Sea surface temperatures and salinity profiles in the Baltic Sea have been analyzed under different climate conditions using a 3D coupled ice-ocean model. As a reference, hindcast simulations for the period 1980-93 have been performed using observed three-hourly meteorological forcing fields and observed monthly river runoff. The results are compared with available observations from monitoring stations. The observed Baltic Sea climate is well reproduced by the model. Furthermore, two sets of 9-year time slice experiments have been performed using results from an atmospheric regional climate model as forcing. One of the time slice sets represents pre-industrial greenhouse conditions (control simulation), and the other set represents a global warming condition with a 150% increase in equivalent CO(2) concentrations (scenario simulation) with lateral boundary conditions from the global atmosphere-ocean general circulation model, HadCM2. To simulate river runoff, a large-scale hydrological model has been applied. As the time slices are too short to properly spin up initial stratification for future climate, salinity is treated as an uncertainty factor. An extreme condition is obtained by integrating the Baltic Sea model for a period of 100 years while assuming that no salt water inflow will occur in the future. Salinity in the Gotland Basin decreases in the surface layer by about 3 to 4 psu and in the bottom layer by about 6 to 6.5 psu. The final quasi-equilibrium is characterized by salinities of 2.8 psu (minimum at the surface) to 6.5 psu (maximum at the bottom). The area averaged annual mean sea surface temperature change between scenario and control run is about 2.3 degreesC. The warming in different seasons is almost the same. The computational effective time slice approach in dynamical downscaling experiments is regarded as a feasible technique to regionalize global climate change experiments in the Baltic Sea.

  • 218.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Regional ocean climate simulations with a 3D ice-ocean model for the Baltic Sea. Part 2: results for sea ice2002In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 19, no 3-4, p. 255-266Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea ice season under changing climate conditions is investigated using a 3D coupled ice-ocean model. Results of multi-year simulations for the period of May 1980 to December 1993 are compared with observations from monitoring stations, ice charts and satellite data. The period 1980-1993 has been selected mainly because of the availability of homogeneous observational data sets for atmospheric variables and river runoff with sufficient quality to force a 3D high resolution Baltic Sea model. The observed seasonal variation of sea ice is well reproduced by the model. Furthermore, two sets of 9-year time slice experiments have been performed using results of an atmospheric regional climate model as forcing, one representing pre-industrial greenhouse conditions (control simulation), and the other a global warming with a 150% increase of equivalent CO(2) concentration (scenario simulation). At the lateral boundaries of the regional climate model, results of the global atmosphere-ocean general circulation model HadCM2 have been prescribed. In the control run, the mean seasonal cycle of ice cover and its variability is simulated realistically compared to observations, but the seasonal ice cover maximum is shifted in time by about 18 days and the simulated mean melting date is delayed. Mild winters are missing in the relatively short control run. The decrease of mean ice extent in the scenario, compared to the control run, is dramatic, reducing from 210 . 10(9) m(2) to 82 . 10(9) m(2) (a relative change of 61%). However, in all scenario years, ice is still formed in the northernmost basin of the Baltic Sea, the Bothnian Bay. The minimum ice extent is 16 . 10(9) m(2) (for comparison: the area of the Bothnian Bay is about twice as large). The mean number of ice days decreases significantly. In the fast ice zone of the Bothnian Bay the mean ice season is reduced by 40 days. The ice in the scenario run is thinner with less snow on top. In the central Bothnian Bay, mean maximum annual ice thickness is reduced by 25 cm from 54 to 29 cm. Model dependent uncertainties are discussed.

  • 219.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Simulated water and heat cycles of the Baltic Sea using a 3D coupled ice-ocean model2001In: third study conference on BALTEX, / [ed] J. Meywerk, 2001, p. 161-162Conference paper (Other academic)
  • 220.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    The doubly stratified regime: turbulence closures for an OGCM of the Baltic Sea.2005In: Marine Turbulence: Theories, Observations, and Models. Results of the CARTUM Project, / [ed] H. Z. Baumert, J. Simpson, and J. Sündermann, Cambridge University Press, 2005, p. 376-382Chapter in book (Other academic)
  • 221.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    The first Rossby Centre regional climate scenario for the Baltic Sea using a 3D coupled ice-ocean model2001Report (Other academic)
    Abstract [en]

    Temperature, salinity, sea ice and sea leve! in the Baltic Sea have been analyzed under different climate conditions using a 3D coupled ice-ocean mode!. As a reference, hindcast simulations for the period 1980-93 have been performed with observed three-hourly meteorological forcing fields and observed monthly river runoff. The observed Baltic Sea climate is well  reproduced by the mode!. Furthermore, two sets of 9-year time slice experiments have been performed using results of an atmospheric regional climate mode! as forcing, one representing pre-industrial climate conditions (control simulation), and the other one global waiming with a 150% increase of CO2 greenhouse gas concentration (scenario simulation). At the boundaries of the regional climate mode! results of the global atmosphere-ocean general circulation mode! HadCM2 (Hadley Centre) have been prescribed. To simulate river runoff, a large-scale hydrological mode! has been applied. As the time slices are too short to spin up initial stratification for future climate, salinity is treated as uncertainty. An extreme condition is obtained, integrating the Baltic Sea model for 100 years assuming that no salt water inflow occurs in future. The area averaged annual mean sea surface temperature change between scenario and control run is about 2.3 'C. Seasonal variability of the change is small compared to the corresponding 2 m air temperature change. The uncertainty due to unknown future initial conditions is relatively small (largest in summer with -0.5'C). The decrease of mean ice extent in the scenario compared to the control run is dramatic, from 210 • 109m2 to 82 • 109m2 (a relative change of 61 % ). However, in all years ice can still be found in the Bothnian Bay. The minimum ice extent is I 6 • 109m2 (for comparison: the area of the Bothnian Bay is about twice as !arge). The mean number of ice days decreases significantly, too. In the fast ice zone of the Bothnian Bay (Kemi) the mean ice season becomes 40 days shorter. The ice in the scenario run is thinner with less snow on top. In the·central Bothnian Bay mean maximum annual ice thickness is reduced by 25 cm from 54 to 29 cm. Mode! dependent uncertainties are discussed.

  • 222.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    The use of the k – e turbulence model within the Rossby Centre regional ocean climate model: parameterization development and results2000Report (Other academic)
  • 223.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Andersson, H. C.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustafsson, B. G.
    Kuznetsov, Ivan
    SMHI, Research Department, Oceanography.
    Muller-Karulis, B.
    Neumann, T.
    Savchuk, O. P.
    Hypoxia in future climates: A model ensemble study for the Baltic Sea2011In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, article id L24608Article in journal (Refereed)
    Abstract [en]

    Using an ensemble of coupled physical-biogeochemical models driven with regionalized data from global climate simulations we are able to quantify the influence of changing climate upon oxygen conditions in one of the numerous coastal seas (the Baltic Sea) that suffers worldwide from eutrophication and from expanding hypoxic zones. Applying various nutrient load scenarios we show that under the impact of warming climate hypoxic and anoxic areas will very likely increase or at best only slightly decrease (in case of optimistic nutrient load reductions) compared to present conditions, regardless of the used global model and climate scenario. The projected decreased oxygen concentrations are caused by (1) enlarged nutrient loads due to increased runoff, (2) reduced oxygen flux from the atmosphere to the ocean due to increased temperature, and (3) intensified internal nutrient cycling. In future climate a similar expansion of hypoxia as projected for the Baltic Sea can be expected also for other coastal oceans worldwide. Citation: Meier, H. E. M., H. C. Andersson, K. Eilola, B. G. Gustafsson, I. Kuznetsov, B. Muller-Karulis, T. Neumann, and O. P. Savchuk (2011), Hypoxia in future climates: A model ensemble study for the Baltic Sea, Geophys. Res. Lett., 38, L24608, doi:10.1029/2011GL049929.

  • 224.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    ECOSUPPORT: A Pilot Study on Decision Support for Baltic Sea Environmental Management2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 529-533Article in journal (Other academic)
  • 225.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Arheimer, Berit
    SMHI, Research Department, Hydrology.
    Blenckner, Thorsten
    Chubarenko, Boris
    Donnelly, Chantal
    SMHI, Research Department, Hydrology.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustafsson, Bo G.
    Hansson, Anders
    Havenhand, Jonathan
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Kuznetsov, Ivan
    MacKenzie, Brian R.
    Muller-Karulis, Barbel
    Neumann, Thomas
    Niiranen, Susa
    Piwowarczyk, Joanna
    Raudsepp, Urmas
    Reckermann, Marcus
    Ruoho-Airola, Tuija
    Savchuk, Oleg P.
    Schenk, Frederik
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Vali, Germo
    Weslawski, Jan-Marcin
    Zorita, Eduardo
    Comparing reconstructed past variations and future projections of the Baltic Sea ecosystem-first results from multi-model ensemble simulations2012In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 7, no 3, article id 034005Article in journal (Refereed)
    Abstract [en]

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

  • 226.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Arheimer, Berit
    SMHI, Research Department, Hydrology.
    Donnelly, Chantal
    SMHI, Research Department, Hydrology.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustafsson, Bo G.
    Kotwicki, Lech
    Neset, Tina-Simone
    Niiranen, Susa
    Piwowarczyk, Joanna
    Savchuk, Oleg P.
    Schenk, Frederik
    Weslawski, Jan Marcin
    Zorita, Eduardo
    Ensemble Modeling of the Baltic Sea Ecosystem to Provide Scenarios for Management2014In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 43, no 1, p. 37-48Article in journal (Refereed)
    Abstract [en]

    We present a multi-model ensemble study for the Baltic Sea, and investigate the combined impact of changing climate, external nutrient supply, and fisheries on the marine ecosystem. The applied regional climate system model contains state-of-the-art component models for the atmosphere, sea ice, ocean, land surface, terrestrial and marine biogeochemistry, and marine food-web. Time-dependent scenario simulations for the period 1960-2100 are performed and uncertainties of future projections are estimated. In addition, reconstructions since 1850 are carried out to evaluate the models sensitivity to external stressors on long time scales. Information from scenario simulations are used to support decision-makers and stakeholders and to raise awareness of climate change, environmental problems, and possible abatement strategies among the general public using geovisualization. It is concluded that the study results are relevant for the Baltic Sea Action Plan of the Helsinki Commission.

  • 227.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustafsson, B.
    Stockholm Resilience Centre/Baltic Nest Institute, Stockholm University, Stockholm, Sweden.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Transient scenario simulations for the Baltic Sea Region during the 21st century2011Report (Other academic)
    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 have been 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). In this study we focussed on annual and seasonal mean changes of ecological quality indicators describing the environmental status of the Baltic Sea. In correspondence with earlier studies we found that the impact of changing climate on the Baltic biogeochemistry might be significant. Assuming reference loadings the water quality in all climate scenarios is reduced at the end of the century. The impact of nutrient load reductions according to the BSAP will be less effective in future climate compared to present climate. However, the results of the pessimistic business-as-usual scenario suggest that policy makers should act to avoid much worse environmental conditions than today.

  • 228.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Andréasson, Johan
    SMHI, Professional Services.
    Broman, Barry
    SMHI, Research Department, Climate research - Rossby Centre.
    Graham, Phil
    SMHI, Professional Services.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Persson, Gunn
    SMHI, Professional Services.
    Climate change scenario simulations of wind, sea level, and river discharge in the Baltic Sea and Lake Mälaren region – a dynamical downscaling approach from global to local scales2006Report (Other academic)
    Abstract [en]

    A regional climate model (RCM) and oceanographic, hydrological and digital elevation models were applied to study the impact of climate change on surface wind, sea level, river discharge, and flood prone areas in the Baltic Sea region. The RCM was driven by two global models and two emission scenarios. According to the four investigated regional scenario simulations, wind speed in winter is projected to increase between 3 and 19% as an area average over the Baltic Sea. Although extremes of the wind speed will increase about as much as the mean wind speed, sea level extremes will increase more than the mean sea level, especially along the eastern Baltic coasts. In these areas projected storm events and global average sea level rise may cause an increased risk for flooding. However, the Swedish east coast will be less affected because mainly the west wind component in winter would increase and because land uplift would compensate for increased sea levels, at least in the northern parts of the Baltic. One of the aims of the downscaling approach was to investigate the future risk of flooding in the Lake Mälaren region including Stockholm city. In Stockholm the 100-year surge is projected to change between -51 and 53 cm relative to present mean sea level suggesting that in the city the risk of flooding from the Baltic Sea is relatively small because the critical height of the jetty walls will not be exceeded. Lake Mälaren lies just to the west of Stockholm and flows directly into the Baltic Sea to the east. This study addresses also the question of how the water level in Lake Mälaren may be affected by climate change by incorporating the following three contributing components into an analysis: 1) projected changes to hydrological inflows to Lake Mälaren, 2) changes to downstream water levels in the Baltic Sea, and 3) changes in outflow regulation from the lake. The first component is analyzed using hydrological modeling. The second and third components employ the use of a lake discharge model. An important conclusion is that projected changes to hydrological inflows show a stronger impact on lake levels than projected changes in water level for the Baltic Sea. Furthermore, an identified need for increased outflow capacity from the lake for the present climate does not diminish with projections of future climate change. The tools developed in this work provide valuable inputs to planning for both present and future operations of water level in Lake Mälaren. Based on the oceanographic and hydrological scenario simulations, flood prone areas were analysed in detail for two municipalities, namely Ekerö and Stockholm. The GIS analysis of both municipalities indicates a series of affected areas. However, in case of the 100-year flood (0.65 m above the mean lake level) in present climate or even in case of the maximum probable flood (1.48 m above the mean lake level) the potential risks will be relatively low.

  • 229.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Broman, Barry
    SMHI, Research Department, Climate research - Rossby Centre.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Modelling Sea Level Variability in Different Climates of the Baltic Sea2004In: Fourth Study Conference on BALTEX: Conference Proceedings / [ed] Hans-Jörg Isemer, Risø National Laboratory Technical University of Denmark GKSS Forschungszentrum Geesthacht GmbH , 2004, p. 170-171Conference paper (Other academic)
  • 230.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Broman, Barry
    SMHI, Research Department, Climate research - Rossby Centre.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Simulated sea level in past and future climates of the Baltic Sea2004In: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 27, no 1, p. 59-75Article in journal (Refereed)
    Abstract [en]

    Sea levels of the Baltic Sea in past and future climates were investigated based upon 6-hourly regional model results. For the future climate, the Rossby Centre Atmosphere Ocean model was used to perform a set of 30 yr time slice experiments. For each of the 2 driving global models HadAM3H and ECHAM4/OPYC3, one control run (1961 to 1990) and 2 scenario runs (2071 to 2100) based upon the scenarios A2 and B2 of the Special Report on Emission Scenarios (SRES) were conducted. To estimate uncertainties in the global and regional models, 3 sea level scenarios for the Baltic Sea were compiled assuming global average sea level rises between 0.09 and 0.88 m and considering land uplift and the impact of regional changes in wind direction and velocity from the time slice experiments. In the scenarios forced with ECHAM4/OPYC3 the mean sea level between October and April increases significantly compared to the control climate, and storm surges increase even more than monthly mean sea level. In the scenarios forced with HadAM3H the changes are mostly not significant. Depending on the sea level rise, the risk of flooding at the coasts may either decrease in the entire Baltic, or it may increase, especially at the eastern ends of the Gulf of Finland and Gulf of Riga and in Gdansk Bay. Here, maximum changes of about 1 m are found in the winter mean 99% quantiles of the sea level. For the past climate the regional ocean model was forced with reconstructed surface wind fields for 1903 to 1998. The results are close to observations, but storm surges in the western Baltic are underestimated.

  • 231.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Christensen, Ole Bössing
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Lorenz, Philip
    Rockel, Burkhardt
    Zorita, Eduardo
    Selected examples of the added value of regional climate models2009In: / [ed] Rockel, B., Bärring, L and Reckermann, M., 2009, p. 54-55Conference paper (Other academic)
  • 232.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Simulated water and heat cycles of the Baltic Sea using a 3D coupled atmosphere-ice - ocean model2002In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 7, no 4, p. 327-334Article in journal (Refereed)
    Abstract [en]

    The heat and water cycles of the Baltic Sea are calculated utilizing multi-year model simulations. This is one of the major objectives of the BALTEX program. For the period 1988-1993, results of a 3D ice-ocean model forced with observed atmospheric surface fields are compared with results of a fully coupled atmosphere-ice-ocean model using re-analysis data at the lateral boundaries. The state-of-the-art coupled model system has been developed for climate study purposes in the Nordic countries. The model domain of the atmosphere model covers Scandinavia, Europe and parts of the North Atlantic whereas the ocean model is limited to the Baltic Sea. The annual and monthly mean heat budgets for the Baltic Sea are calculated from the dominating surface fluxes, i.e. sensible heat, latent heat, net longwave radiation and solar radiation to the open water or to the sea ice. The main part of the freshwater inflow to the Baltic is the river runoff. A smaller part of about 11 % is added from net precipitation. The heat and water cycles are compared with the results of a long-term simulation (1980-1993) using the stand-alone Baltic Sea model forced with observed atmospheric surface fields. In general, both approaches, using the uncoupled or coupled Baltic Sea model, give realistic estimates of the heat and water cycles and are in good agreement with results of other studies. However, in the coupled model the parameterizations of the latent heat flux and the incoming longwave radiation need to be improved.

  • 233.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Broman, Barry
    SMHI, Research Department, Climate research - Rossby Centre.
    Piechura, J
    The major Baltic inflow in January 2003 and preconditioning by smaller inflows in summer/autumn 2002: a model study2004In: Oceanologia, ISSN 0078-3234, Vol. 46, no 4, p. 557-579Article in journal (Refereed)
    Abstract [en]

    Using the results of the Rossby Centre Ocean model (RCO) the Baltic inflows in summer/autumn 2002 and January 2003 have been studied. The model results were extracted from a long simulation with observed atmospheric forcing Starting in May 1980. In RCO a bottom boundary layer model was embedded. Both the Smaller inflows and the major inflow in January 2003 are simulated in good agreement with observations. We found that a total of 222 km(3) water entered the Baltic in January: the salinity of 94 km(3) was greater than 17 PSU. In August/September 2002 the outflow through the Sound and inflow across the Darss Sill were simulated. The net inflow volume amounted to about 50 km(3).

  • 234.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Coward, Andrew C.
    James Renell Div,. Southhampton Oceanogr. Centre.
    Nycander, Jonas
    MISU.
    Döös, Kristofer
    MISU.
    RCO – Rossby Centre regional Ocean climate model: model description (version 1.0) and first results from the hindcast period 1992/931999Report (Other academic)
    Abstract [en]

    Within SWECLIM a 3D fully coupled ice-ocean model has been developed based on the massively parallel OCCAM code from Southampton. Compared to the global OCCAM the model has to be adopted to Baltic Sea conditions with implementations of high-frequent atmospheric forcing fields in connection with adequate bulk formulae for wind stress, heat uxes and freshwater uxes, solar radiation, river runoff, active open boundary conditions, a second-order moment turbulence closure scheme and a dynamic-thermodynamic sea ice model. Thereby, state-of-the-art sub-models and parameterizations have been used. RCO is the first 3D coupled ice-ocean model for the Baltic Sea with the above mentioned specifications suitable for use on mpp computers like CRAY-T3E's. Thus, a milestone for 3D ocean model development has been set. No other model is as fast as RCO. The performance has been improved significantly using advanced algorithms to optimize processor maps. This guarantees work load balance between the different processors. From now on it is possible to perform longterm simulations (10 years) within SWECLIM using a sufficiently resolved 3D Baltic Sea model. The open boundary conditions have been tested. They allow waves to radiate out of the model domain and signals prescribed at the border to in uence the model interior. No significant trends (like emptying or filling) have been observed which might prevent longer integrations of the system. An option has been included in RCO for active open boundary conditions also for temperature and salinity. For the first time the turbulence closure model has been tested within a 3D model in all Baltic sub-basins. The new flux boundary conditions for turbulent kinetic energy parameterizing breaking surface waves perform well. First results for the hindcast period 1992/93 are presented. Therefor, realistic atmospheric, runoff and boundary data have been used. The model is initialized using observed profile temperature and salinity data. A spin-up period of 3 months starting in May is sufficient to smooth out artificial gradients from the initialization procedure and to turn in basin wide volume changes correctly. The model results have been compared to sea level, sea surface temperature, temperature/salinity profile and ice thickness/compactness data with good agreement. Basin wide volume changes as well as daily sea level oscillations are simulated surprisingly good. Sea surface temperatures follow the observed seasonal cycle. Up- and downwelling events in RCO occur as observed with the right frequency and area extent but the sst's tend to be colder in upwelling and warmer in downwelling regions compared to observations. Mixed layer depths, which are important for the ocean heat content, agree well with previous model studies which are validated against observations intensively (Meier, 1996). The water exchange between Baltic and North Sea crucial for multi-year integrations is modelled realistically. Especially the salt water inflow in January 1993 can be reproduced. The bottom water in Bornholm Basin is replaced by new water originating from the North Sea but maximum observed bottom salinities at Bornholm Deep are underestimated by 1-2 PSU. Freezing, breakup date and maximum ice extent are in good correspondence with observations. Improved parameterizations result in modelled ice thicknesses as observed whereas other authors report too large ice thicknesses and delayed ice melting (e.g., Haapala and Lepparanta,1996). Multi-year simulations including mild, normal and severe winters will be necessary to elucidate this problem further. A comparison between an experiment with full dynamic-thermodynamics and one without dynamic effects reveals the importance of ice advection under wind influence. A process study from the beginning of February 1993 showed that under strong wind conditions a hole in the ice coverage can open with the size of half of the Bothnian Bay. At the end of January 1993 the Bothnian Bay, the coastal area of the Bothnian Sea and the eastern parts of the Gulf of Finland are ice covered. A couple of days later westerly winds led to wide open areas in the western Bothnian Bay while ice piled up at the eastern coasts to a correct amount. This phenomenon can be modelled only with ice dynamics included. The aim of SWECLIM is to increase our knowledge of the effects of climate change in Sweden and the other Nordic countries. Therefor, it is necessary to understand the present climate. For the Baltic Sea even the knowledge about the present mean state and its transients is rather poor. Only a small number of long-time observations like sea level records (for example from Stockholm, see Ekman (1988)), maximum annual ice extent (e.g., Palosuo, 1953; Seina and Palosuo, 1993) or temperature and salinityprofiles from monitoring stations in some of the sub-basins (e.g., Matthaus and Frank,1992) are available. These informations are not enough to understand the driving mechanisms of mean horizontal and vertical transports of energy, momentum and matter. 3D Baltic Sea models like RCO will close this knowledge gap in future. Thereby, it will be possible to close the water and energy cycle of the Baltic catchment area, a final goal of BALTEX. By applying atmospheric forcing data from scenario simulations in one- or two-way coupled mode it will be possible to make predictions of climate change for the Baltic Sea. Impact studies of the future marine environment will be available using detailed highly resolved information from RCO. This report presents a powerful tool for solving these and other tasks.

  • 235.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Faxen, T
    A multiprocessor coupled ice-ocean model for the Baltic Sea: Application to salt inflow2003In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 108, no C8, article id 3273Article in journal (Refereed)
    Abstract [en]

    Within the Swedish Regional Climate Modeling Program, SWECLIM, a three-dimensional (3-D) coupled ice-ocean model for the Baltic Sea has been developed to simulate physical processes on timescales of hours to decades. The code has been developed based on the massively parallel version of the Ocean Circulation Climate Advanced Modeling (OCCAM) project of the Bryan-Cox-Semtner model. An elastic-viscous-plastic ice rheology is employed, resulting in a fully explicit numerical scheme that improves computational efficiency. An improved two-equation turbulence model has been embedded to simulate the seasonal cycle of surface mixed layer depths as well as deepwater mixing on decadal timescale. The model has open boundaries in the northern Kattegat and is forced with realistic atmospheric fields and river runoff. Optimized computational performance and advanced algorithms to calculate processor maps make the code fast and suitable for multi-year, high-resolution simulations. As test cases, the major salt water inflow event in January 1993 and the stagnation period 1980-1992, have been selected. The agreement between model results and observations is regarded as good. Especially, the time evolution of the halocline in the Baltic proper is realistically simulated also for the longer period without flux correction, data assimilation, or reinitialization. However, in particular, smaller salt water inflows into the Bornholm Basin are underestimated, independent of the horizontal model resolution used. It is suggested that the mixing parameterization still needs improvements. In addition, a series of process studies of the inflow period 1992/1993 have been performed to show the impact of river runoff, wind speed, and sea level in Kattegat. Natural interannual runoff variations control salt water inflows into the Bornholm Basin effectively. The effect of wind speed variation on the salt water flux from the Arkona Basin to the Bornholm Basin is minor.

  • 236.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Halkka, A
    Simulated distributions of Baltic Sea-ice in warming climate and consequences for the winter habitat of the Baltic ringed seal2004In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 33, no 4-5, p. 249-256Article in journal (Refereed)
    Abstract [en]

    Sea-ice in the Baltic Sea in present and future climates is investigated. The Rossby Centre Regional Atmosphere-Ocean model was used to perform a set of 30-year-long time slice experiments. For each of the two driving global models HadAM3H and ECHAM4/OPYC3, one control run (1961-1990) and two scenario runs (2071-2100) based upon the SIRES A2 and B2 emission scenarios were conducted. The future sea-ice volume in the Baltic Sea is reduced by 83% on average. The Bothnian Sea, large areas of the Gulf of Finland and Gulf of Riga, and the outer parts of the southwestern archipelago of Finland will become ice-free in the mean. The presented scenarios are used to study the impact of climate change on the Baltic ringed seal (Phoca hispida botnica). Climate change seems to be a major threat to all southern populations. The only fairly good winter sea-ice habitat is found to be confined to the Bay of Bothnia.

  • 237.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Modelling the changing climate of the Baltic Sea.2006Report (Other academic)
  • 238.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Edman, Moa
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Placke, Manja
    Neumann, Thomas
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Brunnabend, Sandra-Esther
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Frauen, Claudia
    Friedland, Rene
    Groger, Matthias
    SMHI, Research Department, Oceanography.
    Gustafsson, Bo G.
    Gustafsson, Erik
    Isaev, Alexey
    Kniebusch, Madline
    Kuznetsov, Ivan
    Mueller-Karulis, Baerbel
    Omstedt, Anders
    Ryabchenko, Vladimir
    Saraiva, Sofia
    Savchuk, Oleg P.
    Assessment of Eutrophication Abatement Scenarios for the Baltic Sea by Multi-Model Ensemble Simulations2018In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 5, article id UNSP 440Article in journal (Refereed)
  • 239.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Edman, Moa
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Placke, Manja
    Neumann, Thomas
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Brunnabend, Sandra-Esther
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Frauen, Claudia
    Friedland, Rene
    Groger, Matthias
    SMHI, Research Department, Oceanography.
    Gustafsson, Bo G.
    Gustafsson, Erik
    Isaev, Alexey
    Kniebusch, Madline
    Kuznetsov, Ivan
    Muller-Karulis, Barbel
    Naumann, Michael
    Omstedt, Anders
    Ryabchenko, Vladimir
    Saraiva, Sofia
    Savchuk, Oleg P.
    Assessment of Uncertainties in Scenario Simulations of Biogeochemical Cycles in the Baltic Sea2019In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 6, article id UNSP 46Article in journal (Refereed)
  • 240.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Future projections of ecological patterns in the Baltic Sea2011Report (Other academic)
    Abstract [en]

    The impact of changing climate on Baltic Sea biogeochemical cycles at the end of the 21st century was studied using a three-dimensional coupled physical-biogeochemical model. Four climate change scenarios using regionalized data from two General Circulation Models (GCMs) and two greenhouse gas emission scenarios (A2, B2) have been investigated. In this study we have focused on maps of annual and seasonal mean changes of ecological quality indicators. We found that the impact of changing climate on the horizontal distribution of ecological parameters might be significant. For instance, in the scenario simulation with the largest changes secchi depth might decrease by up to 2 m in some regions. However, due to reduced stratification also increased secchi depths might occur.

  • 241.
    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)
  • 242.
    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)
  • 243.
    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)
  • 244.
    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.

  • 245.
    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.

  • 246.
    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.

  • 247.
    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.

  • 248.
    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)
  • 249.
    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.

  • 250.
    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.

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