January 22, 2018: FB1 seminar

11:00, lecture hall west, Düsternbrooker Weg 20

Abstract:
In 2016 a new working group at the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) on regional climate system dynamics was established. Our research group focusses on regional climate modeling and analysis for the Baltic Sea region. Our goal is to understand ocean dynamics and biogeochemical cycling since the formation of the Baltic Sea after the last ice age and to project future climate until the end of the 21st century. Based upon a well-established environmental monitoring program, long-term data sets are generated by IOW operationally. Our group analyzes these data and compares observations with regional ocean models. At the same time, we are developing an own regional climate model in collaboration with other research groups within the scientific network Baltic Earth (www.baltic.earth) that will include the atmosphere, the ocean, the sea-ice, the land surface of the catchment area and the marine ecosystem. In this presentation, I will give an overview of recent modeling activities using regional Earth system models and I will present multi-model ensemble simulations for the Baltic Sea region for the period 1850–2100. For the past period 1850–2006, atmospheric, hydrological and nutrient forcings were reconstructed, based on historical measurements. For the future period until 2100, scenario simulations were driven by regionalized global general circulation model (GCM) data using several regional climate system models (RCSMs) 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 caused by biases of RCSMs and GCMs, natural variability and unknown forcing scenarios, different models for the various parts of the Earth system were applied. These simulations constitute the largest ever analyzed multi-model ensemble for the Baltic Sea region allowing, inter alia, the statistical evaluation of the ensemble spread. 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 deoxygenation and eutrophication in the future, depending on the nutrient load scenario. 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 years.

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