BALTEX

The Baltic Sea Experiment

to evaluate in increasing detail regional models used for climate and environmental studies, and to develop strategies for climate and environmental impact assessments,
to obtain better and more comprehensive observations from the entire Baltic Sea basin, including new satellite data, in particular to cope with regional resolution
requirements,
to further develop the numerical regional models for the atmosphere, the land surface including rivers and lakes, and the Baltic Sea including sea ice, and
to lower the uncertainty when closing the energy and water budgets from measurements.

While BALTEX research has met to a large extent BALTEX Phase I objectives, gaps still exist and further research is needed for a more comprehensive fulfilment of the original BALTEX aims. BALTEX research related to this objective therefore mainly contributes to further improving the physical understanding of processes, related modelling capabilities, and the quantitative estimation of important water and energy cycle parameters. Major goals include the evaluation of high-resolution regional models, with the particular perspective to support climate and environmental studies and to develop strategies for climate and environmental impact assessments. The further development of modules for coupled regional models for the atmosphere, the land surface including rivers and lakes, and the Baltic Sea including sea ice will be pursued.

Regional analyses and re-analyses of past conditions are needed to validate regional climate model results for the past and the future. An oceanographic gridded data set for the Baltic Sea, comparable to ERA-40, is currently not available. Also, downscaling of atmospheric analyses to coastal regions is a desirable task. Various data sets may be used for this goal: MESAM of SMHI (possibly with improved resolution), ENSEMBLES data with 25 km resolution forced by ERA-40 (1958-2002), ERA-Interim 4DVAR at 80 km horizontal resolution (1989-2008). A new aspect to take into account in re-analyses is land-use change.

More comprehensive observations from the entire Baltic Sea basin are needed, including new satellite data. Moreover, new ground-based remote sensing methods to measure vertical profiles with high temporal and spatial resolution offer new approaches for model validation. Probability density functions of the temporal and spatial variability based on observations and regional climate models may be applied. Certain problems concerning quantitative precipitation forecasts have not yet been solved, e.g. the accuracy of radar measurements, the required resolution of the gauge network, and related economic implications. Results and methods from large projects in other regions may be adopted for the BALTEX region. National meteorological services have activities in the combined application of radar data, mesoscale analysis techniques (e.g. LAPS), and mesoscale modelling. This yields improved products which may be used also for water management. Uncertainties remain in estimates of precipitation minus evaporation (P-E) and its variations over the Baltic Sea. Sea water salinity may be used to study whether atmospheric models have a correct water budget, provided river run-off is known at sufficient accuracy. While some basin-wide estimates of atmospheric water transport derived from re-analysis data sets agree coincidentally within 10 to 20% with basin-wide runoff estimates, individual components of the water and energy cycle sometimes show a drastic mismatch and even unphysical direction of fluxes. A major future goal therefore remains to establish more reliable estimates of budgets and fluxes, i.e. to close the energy and water budgets at lower uncertainty.

Potential Activities

1.1 Regional analyses and re-analyses with a high resolution and time span
1.2 Evaluation and further development of models
1.3 Improvement of quantitative precipitation forecasts
1.4 Quantification of the energy and water budgets on a high level of confidence

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2. Analysis of climate variability and change, and provision of regional climate projections over the Baltic Sea basin for the 21st century

Goals are

to contribute to detecting regional climate change,
to understand the physical mechanisms behind past climate variability and change, whether of natural or anthropogenic origin, in the BALTEX region; and to contribute
to attribution studies,
to study the balance between large-scale control and locally/regionally generated forcing of the regional climate system, and
to develop projections of future climate variability and change, by means of sensitivity analyses and model studies.

Extended observations of climate parameters are available in the region, which should be exploited in concert with model studies. As for most regions, there are specific regional challenges of global climate change for the Baltic Sea basin. The combined effects of climate change and socio-economic changes are largely unknown at present. BALTEX Phase II contributes to the detection of regional climate change in the Baltic Sea basin, and to a better understanding of the physical mechanisms that are behind climate variability and change. One aim is to discern between natural and anthropogenic causes and thus to contribute to attribution studies. Another is to study the contributions of large-scale control and locally/regionally generated forcing on the Baltic Sea basin climate. A further major aim for BALTEX Phase II is to develop projections of future climate variability and change by means of sensitivity analyses and model studies.

Charting past climate variability and change, and providing regional climate projections for the future over the Baltic Sea basin has become a major research component in BALTEX Phase II.

A successful BALTEX effort related to Objective 2 was the BALTEX Assessment of Climate Change for the Baltic Sea basin (BACC). An update to BACC is currently in preparation (BACC II). The purpose of BACC is to provide the scientific community with an assessment of ongoing climate variations in the Baltic Sea basin. An important element was the description of atmospheric, hydrological, oceanographic and ecosystem changes due to climate variations. The BACC initiative has generated a large activity around the Baltic Sea with more than 80 authors contributing to the assessment, and a close cooperation with HELCOM was initiated. The resulting BACC book was published by Springer in January 2008 (BACC 2008). This work has been an important step towards reviewing and assessing our understanding of climate change for the Baltic Sea basin, including land and water ecosystems. BALTEX shall play an important role in this work in the future. BACC II is being organised through a BALTEX working group, aiming for a new assessment within 5 years.

Potential Activities

2.1 Reconstruction history of climate in the past 200 years, as well as detailed re-analysis of “weather” during the past 40 years
2.2 Detection and attribution of climate change
2.3 Scenarios based on evolving global and regional forcing and response
2.4 Assessment of climate change for the Baltic Sea basin

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3. Provision of improved tools for water management, with an emphasis on extreme hydrological events and long-term changes

Goals are

to further develop and apply coupled atmospheric-hydrological models for improved assessment of the availability of water resources in today’s and future climates,
to develop, validate, and apply different modelling systems in selected river basins to assess the impact of climate variability and change on the hydrological regime including the occurrence and severity of extreme events,
to assess future risk of water shortage and extreme events by explicitly taking account of the societal use of groundwater and surface water resources, as well as man-made changes of land use,
to further develop high-resolution observation and data assimilation methods, shortterm precipitation forecasts, and flood forecasts,
to analyse local drivers (e.g. land use changes) for long-term changes in hydrology, and
to assess past and ongoing hydrological changes.

In the context of BALTEX Phase II research, the envisaged improvement of tools for water management aims particularly at assessing how both present and future climate variability impacts on the water resources in the Baltic Sea basin, and how to quantify and reduce the associated risks caused by climate extremes. This objective is therefore closely related to the former one, however, with a specific water-related focus and tailored for a dedicated user and stakeholder community with its specific requirements. BALTEX Phase II goals include the further development and application of coupled atmospheric-hydrological models to be used for improved assessment of the availability of water resources in today’s and future climates. Different modelling systems shall be applied in selected river basins to assess the impact of climate variability and change on the hydrological regime including the occurrence and severity of extreme events. BALTEX will consider socio-economic drivers by explicitly taking account of the societal use of groundwater and surface water resources, as well as manmade changes of land use, in studies of the future risk of water shortage and impacts of extreme events. In this respect, water resource studies should be introduced to coastal zone management planning. Further goals are the development of flood forecasting models, impact models on the future potential of hydropower (including an assessment of dam safety), the impact on river and lake ice in the future, and assessments of drought risks.

Potential Activities

3.1 High resolution hydrological modelling including flood forecasting and scenario models
3.2 Improvement of parameter estimates for distributed hydrological models
3.3 Coupling hydrological models to regional climate models
3.4 Analysis of the consequences of climate change for hydrology and water resources management
3.5 Hydrological modelling using radar-derived precipitation to improve flood forecasting
3.6 Impact studies on the future hydropower potential with specific consideration of dam safety
3.7 Assessment of the influence of climate change on the occurrence of river and lake ice
3.8 To link water resources studies to coastal zone management
3.9 Assessment of drought risk under changing climate

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4. Biogeochemical cycles in the Baltic Sea basin and transport processes within the regional Earth system under anthropogenic influence

Goals are

to improve the understanding of biogeochemical processes in the sea with special emphasis on the relationship between nutrients and the cycling of organic carbon and CO2,
to identify and quantify biogeochemical transformations on land that affect the input of biogeochemically relevant substances into the Baltic Sea,
to improve the understanding of processes in the atmosphere and at the air/sea interface that control the deposition of nutrients and acidic substances and the exchange of bioactive gases,
to incorporate biogeochemical fluxes, from both land and the atmosphere to the sea, into regional coupled atmosphere-land-ocean models including sea ice, rivers and lakes, and
to foster the coupling of climate and biogeochemical models in order to estimate the consequences of climate change for the regional Earth system of the Baltic Sea basin including the Baltic Sea ecosystem.

The overall aim of this objective is to include biogeochemical processes in the scope of BALTEX research. As biogeochemical cycles are closely interwoven with the hydrological cycle, BALTEX can contribute with its expertise on the water cycle in the Baltic Sea basin. Water as the Earth´s ubiquitous solvent governs the fluxes and reservoirs of biogeochemically relevant elements on land, in the sea and in the atmosphere. A changing water cycle inherently implies a change in the fluxes and reservoirs of these elements.

This research objective rests on two pillars: Firstly, the investigation of the carbon cycle with special emphasis on CO2 and organic carbon in the Baltic Sea and its drainage basin, taking into account fluxes across the atmosphere and sediment interfaces. Here, specific goals are to achieve significant progress in marine ecosystem modelling by aligning biomass production and oxygen depletion with CO2 dynamics, and to assess potential effects of climate change, eutrophication, increasing atmospheric CO2 concentration, and acidic deposition on the carbon cycling in the Baltic Sea and its catchment area; secondly, the extension and combination of existing regional climate models with biogeochemical and ecosystem models in order to achieve a modelling tool which allows an estimation of climate change impacts on the ecosystems of the Baltic Sea and drainage basin. This, in fact, requires a true interdisciplinary approach, bringing together climate and ecosystem researchers and modellers.

Both research priorities of this objective are being supported by the research projects Baltic-C and ECOSUPPORT, which have received support by BONUS, a new joint funding mechanism for the Baltic Sea region by the European Commission and several EU member states. These projects bundle some research activities within this objective, but do not exclude other activities within the scope of this objective.

Baltic-C will involve the development, evaluation, and application of the first fully integrated model framework for the predictive analysis of the functionning and the dynamics of the Baltic Sea organic/inorganic carbon and oxygen systems. This framework will significantly improve the understanding of the relevant physical, chemical, and biological processes and will be supported by and validated against comprehensive observational data. Outcome of the project will be a new integrated model framework that supports the water management of the Baltic Sea and its ecosystem, addressing the consequences of climate change, eutrophication, increasing atmospheric CO2 concentration, and acid deposition.

ECOSUPPORT adresses the need for policy-relevant information on the combined future impacts of climate change and industrial and agricultural practices in the Baltic Sea basin on the Baltic Sea ecosystem. The main aim is to provide a multi-model system tool to support decision makers. The tool is based on scenarios from an existing state-of-the-art coupled atmosphere-ice-ocean-land surface model for the Baltic Sea basin, marine physicalbiogeochemical models of differing complexity, a food web model, statistical fish population models, economic calculations, and new data detailing climate effects on marine biota. The expected outcome of ECOSUPPORT is an advanced modelling tool for scenario simulations of the whole marine ecosystem that can support management strategies to ensure water quality standards, biodiversity and fish stocks under the conditions of climate change.

Potential Activities

4.1. Time series measurements and use of historic data for nutrients, organic carbon and CO2 in the Baltic Sea for process parameterization and model validation;
4.2. Model based (with data assimilation) space-time detailed description of past variability and change in biogeochemical cycles;
4.3. Implementation of the marine CO2 system into and improvement of biogeochemical models;
4.4. Increasing the spatial and temporal resolution of monitoring of the riverine input and atmospheric deposition of nutrients and organic carbon;
4.5. Studies on the gas exchange transfer velocity using new technologies;
4.6. Integration of biogeochemical models into existing coupled regional climate models;
4.7. Model based scenarios on future biogeochemical cycles under changing anthropogenic pressures

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5. Strengthened interaction with decision-makers, with emphasis on global change impact assessments

The involvement of stakeholders and decision makers is an important aspect in BALTEX Phase II. A prominent and successful example of stakeholder involvement in BALTEX Phase II is the collaboration with HELCOM, the Baltic Marine Environment Protection Agency, in sharing the BACC material for a dedicated HELCOM Report. This collaboration will be further strengthened in the scope of BACC II. Other important stakeholders remain the national hydro-meteorological services, but interaction with other stakeholders such as policy decision makers, international organisations, companies and small enterprises in various sectors should also be strengthened and established. A currently ongoing collaboration with BSSSC, the Baltic SeaStates Subregional Co-operation, represents an interface between the scientific community and a network of politicians on the local (sub-regional) scale, broaching the issue of local impacts of regional climate change. This collaboration is planned to be further developed. The selection of topics for stakeholder and policy maker involvement is driven by societal needs and is therefore a dynamical process.

Potential Activities

5.1 Identification of relevant stakeholders and users
5.2 Intensification of contacts between scientists and stakeholders/users
5.3 Organization of stakeholder/user-relevant workshops
5.4 Responding to information requirements of decision makers, among others by BACC II book
5.5 Elaboration of adaptation strategies to climate change in the BALTEX region
5.6 Identification of fundable research activities

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6. Education and outreach at the international level

The rationale for BALTEX Phase II clearly demonstrates the relevance of the programme for various sectors of the society. BALTEX will maintain a broad programme component with the overall objective to strengthen the education and outreach of BALTEX at all relevant levels, ranging from local to international and global. This component of the programme shall promote and facilitate the dissemination, transfer, exploitation, assessment and broad take-up of past and future programme results. The character of the individual measures include in particular i) the creation of awareness, ii) dissemination of results of the programme, and, iii) dedicated education and training measures. The target groups to be addressed in society can be largely divided into 1) stakeholders and users, 2) scientists, 3) students, and 4) the general public.

Potential Activities

6.1 Organisation of BALTEX-related summer schools as well as the integration of BALTEX relevant topics into national and international study programmes including Master and PhD theses
6.2 Preparation of relevant study material for secondary schools
6.3 BALTEX-related evening lectures
6.4 Establishment of a website dedicated to the general public

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