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  • 1. Bal, S.
    et al.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Spangehl, T.
    Cubasch, U.
    On the robustness of the solar cycle signal in the Pacific region2011In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, article id L14809Article in journal (Refereed)
    Abstract [en]

    The potential role of the stratosphere for the 11-year solar cycle signal in the Pacific region is investigated by idealized simulations using a coupled atmosphere-ocean general circulation model. The model includes a detailed representation of the stratosphere and accounts for changes in stratospheric heating rates from prescribed time dependent variations of ozone and spectrally high resolved solar irradiance. Three transient simulations are performed spanning 21 solar cycles each. The simulations use slightly different ozone perturbations representing uncertainties of solar induced ozone variations. The model reproduces the main features of the 20th century observed solar response. A persistent mean sea level pressure response to solar forcing is found for the eastern North Pacific extending over North America. Moreover, there is evidence for a La Nina-like response assigned to solar maximum conditions with below normal SSTs in the equatorial eastern Pacific, reduced equatorial precipitation, enhanced off-equatorial precipitation and an El Nino-like response a couple of years later, thus confirming the response to solar forcing at the surface seen in earlier studies. The amplitude of the solar signal in the Pacific region depends to a great extent on the choice of the centennial period averaged. Citation: Bal, S., S. Schimanke, T. Spangehl, and U. Cubasch (2011), On the robustness of the solar cycle signal in the Pacific region, Geophys. Res. Lett., 38, L14809, doi:10.1029/2011GL047964.

  • 2. Bal, Sourabh
    et al.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Spangehl, Thomas
    Cubasch, Ulrich
    Enhanced residual mean circulation during the evolution of split type sudden stratospheric warming in observations and model simulations2018In: Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences, ISSN 0253-4126, E-ISSN 0973-774X, Vol. 127, no 5, article id 68Article in journal (Refereed)
  • 3. Bal, Sourabh
    et al.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Spangehl, Thomas
    Cubasch, Ulrich
    Variable influence on the equatorial troposphere associated with SSW using ERA-Interim2017In: Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences, ISSN 0253-4126, E-ISSN 0973-774X, Vol. 126, no 2, article id UNSP 19Article in journal (Refereed)
  • 4. Buizza, Roberto
    et al.
    Poli, Paul
    Rixen, Michel
    Alonso-Balmaseda, Magdalena
    Bosilovich, Michael G.
    Bronnimann, Stefan
    Compo, Gilbert P.
    Dee, Dick P.
    Desiato, Franco
    Doutriaux-Boucher, Marie
    Fujiwara, Masatomo
    Kaiser-Weiss, Andrea K.
    Kobayashi, Shinya
    Liu, Zhiquan
    Masina, Simona
    Mathieu, Pierre-Philippe
    Rayner, Nick
    Richter, Carolin
    Seneviratne, Sonia I.
    Simmons, Adrian J.
    Thepaut, Jean-Noel
    Auger, Jeffrey D.
    Bechtold, Michel
    Berntell, Ellen
    Dong, Bo
    Kozubek, Michal
    Sharif, Khaled
    Thomas, Christopher
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Storto, Andrea
    Tuma, Matthias
    Valisuo, Ilona
    Vaselali, Alireza
    ADVANCING GLOBAL AND REGIONAL REANALYSES2018In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 99, no 8, p. ES139-ES144Article in journal (Refereed)
  • 5. Deng, Junjie
    et al.
    Harff, Jan
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    A method for assessing the coastline recession due to the sea level rise by assuming stationary wind-wave climate2015In: OCEANOLOGICAL AND HYDROBIOLOGICAL STUDIES, ISSN 1730-413X, Vol. 44, no 3, p. 362-380Article in journal (Refereed)
    Abstract [en]

    The method introduced in this study for future projection of coastline changes hits the vital need of communicating the potential climate change impact on the coast in the 21th century. A quantitative method called the Dynamic Equilibrium Shore Model (DESM) has been developed to hindcast historical sediment mass budgets and to reconstruct a paleo Digital Elevation Model (DEM). The forward mode of the DESM model relies on paleo-scenarios reconstructed by the DESM model assuming stationary wind-wave climate. A linear relationship between the sea level, coastline changes and sediment budget is formulated and proven by the least square regression method. In addition to its forward prediction of coastline changes, this linear relationship can also estimate the sediment budget by using the information on the coastline and relative sea level changes. Wind climate change is examined based on regional climate model data. Our projections for the end of the 21st century suggest that the wind and wave climates in the southern Baltic Sea may not change compared to present conditions and that the investigated coastline along the Pomeranian Bay may retreat from 10 to 100 m depending on the location and on the sea level rise which was assumed to be in the range of 0.12 to 0.24 m.

  • 6.
    Dieterich, Christian
    et al.
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Wang, Shiyu
    SMHI, Research Department, Climate research - Rossby Centre.
    Väli, Germo
    SMHI, Research Department, Oceanography.
    Liu, Ye
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Evaluation of the SMHI coupled atmosphere-ice-ocean model RCA4-NEMO2013Report (Other academic)
    Abstract [en]

    AbstractThe regional, coupled atmosphere-ice-ocean model RCA4-NEMO developed at the SMHI is evaluated on the basis of an ERA40 hindcast. While the development of the regional climate model is continuing a first assessment is presented here to allow for an orientation about the status guo. RCA4-NEMO in its present form consists of two model components. The regional atmosphere model RCA4 covers the whole of Europe and is interactvely coupled to a North Sea and Baltic Sea ice-ocean model based on NEMO. RCA4-NEMO is currently being used to downscale CMIP5 scenarios for the North Sea and Baltic Sea region for this century. As a part of the validation of RCA4-NEMO we present an analysis and discussion of the hindcast period 1970-1999. The model realization is compared to observational records. Near surface temperatures and heat fluxes compare reasonably well with records of in-situ measurments and satellite derived estimates. For salinities and freshwater fluxes the agreement with observations in not satisfactory yet. The momentum fluxes transferred from the atmosphere to the ice-ocean model are identified as on of the sensitive processes in the coupling of both model components. Except for the freshwater exchange between atmosphere and ocean the climatological near surface properties and corresponding fluxes compare well with climatological estimates for the period 1970-1999.

  • 7. 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.

  • 8. 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.

  • 9.
    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.

  • 10.
    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)
  • 11.
    Höglund, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Ice conditions for maritime traffic in the Baltic Sea in future climate2017In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 22, p. 245-265Article in journal (Refereed)
  • 12.
    Koenigk, Torben
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Caian, Mihaela
    SMHI, Research Department, Climate research - Rossby Centre.
    Nikulin, Grigory
    SMHI, Research Department, Climate research - Rossby Centre.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Regional Arctic sea ice variations as predictor for winter climate conditions2016In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 46, no 1-2, p. 317-337Article in journal (Refereed)
    Abstract [en]

    Seasonal prediction skill of winter mid and high northern latitudes climate from sea ice variations in eight different Arctic regions is analyzed using detrended ERA-interim data and satellite sea ice data for the period 1980-2013. We find significant correlations between ice areas in both September and November and winter sea level pressure, air temperature and precipitation. The prediction skill is improved when using November sea ice conditions as predictor compared to September. This is particularly true for predicting winter NAO-like patterns and blocking situations in the Euro-Atlantic area. We find that sea ice variations in Barents Sea seem to be most important for the sign of the following winter NAO-negative after low ice-but amplitude and extension of the patterns are modulated by Greenland and Labrador Seas ice areas. November ice variability in the Greenland Sea provides the best prediction skill for central and western European temperature and ice variations in the Laptev/East Siberian Seas have the largest impact on the blocking number in the Euro-Atlantic region. Over North America, prediction skill is largest using September ice areas from the Pacific Arctic sector as predictor. Composite analyses of high and low regional autumn ice conditions reveal that the atmospheric response is not entirely linear suggesting changing predictive skill dependent on sign and amplitude of the anomaly. The results confirm the importance of realistic sea ice initial conditions for seasonal forecasts. However, correlations do seldom exceed 0.6 indicating that Arctic sea ice variations can only explain a part of winter climate variations in northern mid and high latitudes.

  • 13. Kotilainen, Aarno T.
    et al.
    Arppe, Laura
    Dobosz, Slawomir
    Jansen, Eystein
    Kabel, Karoline
    Karhu, Juha
    Kotilainen, Mia M.
    Kuijpers, Antoon
    Lougheed, Bryan C.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Moros, Matthias
    Neumann, Thomas
    Porsche, Christian
    Poulsen, Niels
    Rasmussen, Peter
    Ribeiro, Sofia
    Risebrobakken, Bjorg
    Ryabchuk, Daria
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Snowball, Ian
    Spiridonov, Mikhail
    Virtasalo, Joonas J.
    Weckstrom, Kaarina
    Witkowski, Andrzej
    Zhamoida, Vladimir
    Echoes from the Past: A Healthy Baltic Sea Requires More Effort2014In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 43, no 1, p. 60-68Article in journal (Refereed)
    Abstract [en]

    Integrated sediment multiproxy studies and modeling were used to reconstruct past changes in the Baltic Sea ecosystem. Results of natural changes over the past 6000 years in the Baltic Sea ecosystem suggest that forecasted climate warming might enhance environmental problems of the Baltic Sea. Integrated modeling and sediment proxy studies reveal increased sea surface temperatures and expanded seafloor anoxia (in deep basins) during earlier natural warm climate phases, such as the Medieval Climate Anomaly. Under future IPCC scenarios of global warming, there is likely no improvement of bottom water conditions in the Baltic Sea. Thus, the measures already designed to produce a healthier Baltic Sea are insufficient in the long term. The interactions between climate change and anthropogenic impacts on the Baltic Sea should be considered in management, implementation of policy strategies in the Baltic Sea environmental issues, and adaptation to future climate change.

  • 14.
    Kuznetsov, Ivan
    et al.
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Model study on the variability of ecosystem parameters in the Skagerrak-Kattegat area, effect of load reduction in the North Sea and possible effect of BSAP on Skagerrak-Kattegat area2016Report (Other academic)
    Abstract [en]

    Newly developed ecosystem model NEMO-Nordic-SCOBI was applied to Skagerrak - Kattegat area to investigate the variability of some indicators of the ecosystem. Also, two sensitivity runs were performed to investigate possible effect of the Baltic Sea Action Plan (BSAP) and a river loads reduction scenario on the Skagerrak - Kattegat area. The performed investigation could be used “to provide a basis to assist with the interpretation of measurement data before the Intermediate Assessments Eutrophication status assessment”. Comparison of simulation results with observations indicates acceptable model performance. Modeled sea surface salinity, temperature and dissolved inorganic phosphate (DIP) are in good agreement with observations. At the same time, the model has a bias in certain areas of the investigated region for dissolved inorganic nitrogen (DIN) and dissolved silicate during the winter season. However, the model in its current state shows good enough results for the performed investigation. Results of the two sensitivity studies show a decrease of sea surface nutrients concentrations during winter period in both regions. In the Skagerrak area the decrease is due to reduction in river nutrient loads in North Sea. In the Kattegat area there is a decrease of dissolved phosphate due to the implementation of BSAP. At the same time, in both scenarios, no significant changes were obtained for near bottom oxygen or surface layer Chl-a.

  • 15.
    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.

  • 16.
    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.

  • 17.
    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.

  • 18.
    Meier, Markus
    et al.
    SMHI, Research Department, Oceanography.
    Muller-Karulis, Barbel
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Gustafsson, Bo G.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Kuznetsov, Ivan
    SMHI, Research Department, Oceanography.
    Neumann, Thomas
    Ranjbar, Zohreh
    Savchuk, Oleg P.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Impact of Climate Change on Ecological Quality Indicators and Biogeochemical Fluxes in the Baltic Sea: A Multi-Model Ensemble Study2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 558-573Article in journal (Refereed)
    Abstract [en]

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

  • 19.
    Pemberton, Per
    et al.
    SMHI, Research Department, Oceanography.
    Löptien, Ulrike
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Haapala, Jari
    Sea-ice evaluation of NEMO-Nordic 1.0: a NEMO-LIM3.6-based ocean-sea-ice model setup for the North Sea and Baltic Sea2017In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 10, no 8, p. 3105-3123Article in journal (Refereed)
  • 20.
    Schimanke, Semjon
    et al.
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    An algorithm based on sea-level pressure fluctuations to identify major Baltic inflow events2014In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 66, article id 23452Article in journal (Refereed)
    Abstract [en]

    Major Baltic inflows are an important process to sustain the sensitive steady state of the Baltic Sea. We introduce an algorithm to identify atmospheric variability favourable for major Baltic inflows. The algorithm is based on sea-level pressure (SLP) fields as the only parameter. Characteristic SLP pattern fluctuations include a precursory phase of 30 days and 10 days of inflow period. The algorithm identifies successfully the majority of observed major Baltic inflows between 1961 and 2010. In addition, the algorithm finds some occurrences which cannot be related to observed inflows. In these cases with favourable atmospheric conditions, inflows were precluded by contemporaneously existing saline water masses or strong freshwater supply. Moreover, the algorithm clearly identifies the stagnation periods as a lack of SLP variability favourable for MBIs. This indicates that the lack of inflows is mainly a consequence of missing atmospheric forcing during this period. The only striking inflow which is not identified by the algorithm is the event in January 2003. We demonstrate that this is due to the special evolution of SLP fields which are not comparable with any other event. Finally, the algorithm is applied to an ensemble of scenario simulations. The result indicates that the number of atmospheric events favourable for major Baltic inflows increases slightly in all scenarios.

  • 21.
    Schimanke, Semjon
    et al.
    SMHI, Research Department, Oceanography.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    A regional climate model simulation over the Baltic Sea region for the last Millennium2011Report (Other academic)
    Abstract [en]

    Variability and long-term climate change in Fennoscandia is investi-gated in a 1000-year long climate model simulation. We use the Rossby Centre Regional Climate model (RCA3) with boundaryconditions from a General Circulation Model (GCM). Solar variability, changes in orbital parameters and changes in greenhouse gases over the last millennium are used to force the climate models. It is shown that RCA3 generates a warm period corresponding to the Medieval Climate Anomaly (MCA) being the warmest period within the millennium apart from the 20th century. Moreover, an analogy forthe Little Ice Age (LIA) was shown to be the coldest period. The simulated periods are 1100-1299 A.D. for the MCA and 1600-1799 A.D. for the LIA, respectively. This is in agreement with recon-structions and mostly related to changes in the solar irradiance. We found that multi decadal variability has an important impact on the appearance of the MCA and LIA. Moreover, multi decadal variability mayhelp to explain sometimes contradicting reconstructions if these are representative for relatively short non-overlapping periods. In addition to time series, we investigate spatial patterns of temperature, sealevel pressure, precipitation, cloud cover, wind speed and gustiness for annual and seasonal means. Most parameters show the clearest response for the winter season. For instance, winter during the MCAare 1-2.5 K warmer than during the LIA for multi decadal averages.

  • 22.
    Schimanke, Semjon
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Decadal-to-Centennial Variability of Salinity in the Baltic Sea2016In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 29, no 20, p. 7173-7188Article in journal (Refereed)
  • 23.
    Schimanke, Semjon
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    The climate in the Baltic Sea region during the last millennium simulated with a regional climate model2012In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 8, no 5, p. 1419-1433Article in journal (Refereed)
    Abstract [en]

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

  • 24.
    Schimanke, Semjon
    et al.
    SMHI, Research Department, Oceanography.
    Spangehl, T.
    Huebener, H.
    Cubasch, U.
    Variability and trends of major stratospheric warmings in simulations under constant and increasing GHG concentrations2013In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 40, no 7-8, p. 1733-1747Article in journal (Refereed)
    Abstract [en]

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

  • 25.
    Schöld, Sofie
    et al.
    SMHI, Core Services.
    Hellström, Sverker
    SMHI, Core Services.
    Ivarsson, Cajsa-Lisa
    SMHI, Professional Services.
    Kållberg, Per
    SMHI, Research Department, Meteorology.
    Lindow, Helma
    SMHI, Core Services.
    Nerheim, Signild
    SMHI, Professional Services.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Södling, Johan
    SMHI, Professional Services.
    Wern, Lennart
    SMHI, Core Services.
    Vattenståndsdynamik längs Sveriges kust2018Report (Other academic)
    Abstract [sv]

    För att skapa ett samhälle väl anpassat till dagens och framtidens havsnivåer behövs besluts- och planeringsunderlag. Skyddsåtgärder och designnivåer för kustskydd är högaktuella frågor och många aktörer är intresserade av information kring potentiella maxnivåer för vattenstånd på olika tidshorisonter. SMHI har därför analyserat de mätdataserier för havsvattenstånd som idag finns tillgängliga från stationer längs Sveriges kust. Det primära syftet var att ta fram en metod för att beräkna det högsta möjliga havsvattenståndet vid mätstationer längs Sveriges kust. Metoden beskrivs i Schöld m.fl.(2017).

    I föreliggande rapport beskrivs allmänt havsnivåer, mätdata, modeller och de resultat som erhölls från olika analyser av mätdata. Mätstationerna indelades i åtta olika kustområden inom vilka vattenståndet samvarierar. Det väder och de specifika stormbanor, som under de senaste 40 åren orsakat de högsta stormfloderna på olika platser längs den svenska kusten kartlades, och vattenståndsdynamiken vid olika mätstationer studerades.

    Kortvariga höjningar av vattenståndet undersöktes, både med avseende på kraftiga vattenståndshöjningar orsakade av passerande väderssystem och med avseende på förhöjda utgångslägen, som i sin tur kan bidra till att stormfloder blir extra höga.

    Det högsta beräknade havsvattenstånd som presenteras är de högsta möjliga stormfloder som skulle kunna inträffa baserat på empiriska analyser av mätdata vid de olika stationerna. Kända extrema händelser, som ägt rum före det att vattenståndet började registreras, ingår inte eftersom de inte har kunnat kvantifieras. Framtida förändringar av medelvattenståndet orsakade av den globala klimatförändringen behandlas inte i denna rapport.

    Resultaten från studien visar att vattennivåerna i Östersjön generellt blir som högst i Bottenviken och i de södra delarna. De höga vattenstånden i större delen av Östersjön är inte lika höga som på västkusten och i Öresund. I Östersjön förefaller också utgångsläget, havsnivån före stormen, utgöra en större del av den resulterande vattenståndshöjningen. Vid flera stationer i de centrala delarna av Östersjön är havsnivån före storm i stort sett hälften av det högsta beräknade havsvattenståndet. Längs västkusten är istället de nettohöjningar som orsakas av rena stormeffekter den viktigaste stormflodskomponenten. Lokala förhållanden, till exempel om stationen är belägen vid en öppen, rak kust eller inne i en vik, påverkar hur högt vattenståndet kan förväntas bli på en viss plats.

    Analyserna visar att stormfloder skulle kunna bli omkring 20-40 cm högre än hittills observerade maximala nivåer i olika kustområden. En osäkerhetsmarginal på runt +15 cm är lämplig att addera, särskilt i de områden där tidvatten förekommer.

  • 26.
    Wang, Shiyu
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Development and evaluation of a new regional coupled atmosphere-ocean model in the North Sea and Baltic Sea2015In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 67, article id 24284Article in journal (Refereed)
    Abstract [en]

    A new regional coupled model system for the North Sea and the Baltic Sea is developed, which is composed of the regional setup of ocean model NEMO, the Rossby Centre regional climate model RCA4, the sea ice model LIM3 and the river routing model CaMa-Flood. The performance of this coupled model system is assessed using a simulation forced with ERA-Interim reanalysis data at the lateral boundaries during the period 1979-2010. Compared to observations, this coupled model system can realistically simulate the present climate. Since the active coupling area covers the North Sea and Baltic Sea only, the impact of the ocean on the atmosphere over Europe is small. However, we found some local, statistically significant impacts on surface parameters like 2m air temperature and sea surface temperature (SST). A precipitation-SST correlation analysis indicates that both coupled and uncoupled models can reproduce the air-sea relationship reasonably well. However, the coupled simulation gives slightly better correlations even when all seasons are taken into account. The seasonal correlation analysis shows that the air-sea interaction has a strong seasonal dependence. Strongest discrepancies between the coupled and the uncoupled simulations occur during summer. Due to lack of air-sea interaction, in the Baltic Sea in the uncoupled atmosphere-standalone run the correlation between precipitation and SST is too small compared to observations, whereas the coupled run is more realistic. Further, the correlation analysis between heat flux components and SST tendency suggests that the coupled model has a stronger correlation. Our analyses show that this coupled model system is stable and suitable for different climate change studies.

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