Dr. Hagen Radtke
Seestrasse 15
D-18119 Rostock
Hagen Radtke is a biogeochemical modeller with a background in physics. Together with Thomas Neumann, he leads the Biogeochemical Modelling working group at IOW.
Research interests
System understanding of the Baltic Sea
The Baltic Sea is a complex ecosystem shaped by numerous interactions between physical, chemical, and biological processes. An integrated, interdisciplinary understanding is therefore essential to assess its future development, particularly with regard to key challenges such as anoxia and eutrophication.
The goal of my research is to advance the development of the biogeochemical model ERGOM in close collaboration with colleagues from different disciplines. By synthesising detailed process understanding of individual components, we aim to achieve a comprehensive system understanding of the Baltic Sea.
Efficient biogeochemical modelling
The vision of interactive, cross-disciplinary model development often encounters technical limitations in practice: traditional biogeochemical models are computationally expensive and difficult to access for non-programmers. To overcome this barrier, I develop new methods that make the modelling process more efficient and more flexible.
Two key approaches are:
- Code Generation Tool: Instead of formulating biological equations directly in source code, they are defined in a simplified description language. A tool I developed automatically translates them into various programming languages – for example Fortran for classical high-performance models, or Python and R for interactive “toy models”.
- GPU-based offline model roboelf: In this approach, the physical dynamics are computed only once; the subsequent biogeochemical simulations can then be carried out very rapidly on standard consumer GPUs – without the need for a supercomputing centre.
In the long term, I aim to establish a modular toolchain for ERGOM that comprises a hierarchy of models, ranging from fast, interactive variants for exploratory experiments to high-resolution simulations for state-of-the-art research applications.
Teaching
I am a lecturer in the module “Fundamentals of Marine Biology – Oceanography”, which is part of the master’s programme “Marine Biology” at the University of Rostock. This module provides basic knowledge in physical oceanography. The lecture notes (in German only) can be found here.
Publications
2025
A.A. Anschütz, J.M. Lencina-Avila, G. Rehder, B. Cahill, T. Neumann, …, H. Radtke, 2025. „Direct effects of ocean alkalinity enhancement in the Baltic Sea – results from in-silico experiments.“ Frontiers in Climate 7, 1450468. https://doi.org/10.3389/fclim.2025.1450468
L. Barghorn, H.E.M. Meier, H. Radtke, T. Neumann, L. Naumov, 2025. „Warm saltwater inflows strengthen oxygen depletion in the western Baltic Sea.“ Climate Dynamics 63 (1), 1-14. https://doi.org/10.1007/s00382-024-07501-x
R. Friedland, T. Neumann, S. Piehl, H. Radtke, G. Schernewski, 2025. „Characterization of river plume dynamics for a better water quality management.“ Frontiers in Marine Science 12, 1617660. https://doi.org/10.3389/fmars.2025.1617660
M. Voss, P. Holtermann, S. Ahmerkamp, D.L.A. Martínez, B. Cahill, …, H. Radtke, ... 2025. „Coastal zones of the Baltic Sea in the Anthropocene: Current state and the impact of climate change.“ Estuarine, Coastal and Shelf Science, 109504. https://doi.org/10.1016/j.ecss.2025.109504
2024
C. Dieterich, H. Radtke, 2024. „Higher quantiles of sea levels rise faster in Baltic Sea Climate projections.“ Climate Dynamics, 1-11. https://doi.org/10.1007/s00382-023-07094-x
S. Karsten, H. Radtke, M. Gröger, H.T.M. Ho-Hagemann, H. Mashayekh, 2024. „Flux coupling approach on an exchange grid for the IOW Earth System Model (version 1.04. 00) of the Baltic Sea region.“ Geoscientific Model Development 17 (4), 1689-1708. https://doi.org/10.5194/gmd-17-1689-2024
J. Rooze, M.A. Zeller, M. Gogina, P. Roeser, J. Kallmeyer, M. Schönke, H. Radtke, M.E. Böttcher, 2024. „Bottom-trawling signals lost in sediment: A combined biogeochemical and modeling approach to early diagenesis in a perturbed coastal area of the southern Baltic Sea.“ Science of The Total Environment, 906, 167551. https://doi.org/10.1016/j.scitotenv.2023.167551
G. Väli, H.E.M. Meier, T. Liblik, H. Radtke, K. Klingbeil, U. Gräwe, U. Lips, 2024. „Submesoscale processes in the surface layer of the central Baltic Sea: A high-resolution modelling study.“ Oceanologia. https://doi.org/10.1016/j.oceano.2023.11.002
2023
L. Barghorn, H.E.M. Meier, H. Radtke, 2023. „Changes in Seasonality of Saltwater Inflows Caused Exceptional Warming Trends in the Western Baltic Sea.“ Gephysical Research Letters 50, 12. https://doi.org/10.1029/2023GL103853
F. Börgel, T. Neumann, J. Rooze, H. Radtke, L. Barghorn, H.E.M. Meier, 2023. „Deoxygenation of the Baltic Sea during the last millennium.“ Frontiers in Marine Science, 10, 1077. https://doi.org/10.3389/fmars.2023.1174039
F. Börgel, M. Gröger, H.E.M. Meier, C. Dutheil, H. Radtke, L. Borchert, 2023. „The impact of Atlantic Multidecadal Variability on Baltic Sea temperatures limited to winter.“ npj Climate and Atmospheric Science 6 (1), 64. https://doi.org/10.1038/s41612-023-00373-8
H.E.M. Meier, L. Barghorn, F. Börgel, M. Gröger, L.. Naumov, H. Radtke, 2023. „Multidecadal climate variability dominated past trends in the water balance of the Baltic Sea watershed.“ npj climate and atmospheric science, 6, 58. https://doi.org/10.1038/s41612-023-00380-9
L. Naumov, T. Neumann, H. Radtke, H.E.M. Meier, 2023. „Limited ventilation of the central Baltic Sea due to elevated oxygen consumption.“ Frontiers in Marine Science, 10, 694. https://doi.org/10.3389/fmars.2023.1175643
J. Rooze, H. Jung, H. Radtke, 2023. „A novel Eulerian model based on central moments to simulate age and reactivity continua interacting with mixing processes.“ Geoscientific Model Development, 16, 7107–7121, https://doi.org/10.5194/gmd-16-7107-2023
L. Umlauf, K. Klingbeil, H. Radtke, R. Schwefel, J. Bruggeman, P. Holtermann, 2023. „Hydrodynamic Control of Sediment‐Water Fluxes: Consistent Parameterization and Impact in Coupled Benthic‐Pelagic Models.“ Journal of Geophysical Research: Oceans 128 (6), e2023JC019651. https://doi.org/10.1029/2023JC019651
2022
M. Gröger, M. Placke, H.E.M. Meier, F. Börgel, S.-E. Brunnabend, C. Dutheil, U. Gräwe, M. Hieronymus, T. Neumann, H. Radtke, S. Schimanke, J. Su, G. Väli, 2022. „The Baltic Sea Model Intercomparison Project (BMIP) – a platform for model development, evaluation, and uncertainty assessment.“ Geoscientific Model Development 15, 8613–8638. https://doi.org/10.5194/gmd-15-8613-2022
T. Neumann, H. Radtke, B. Cahill, M. Schmidt, G. Rehder, 2022. „Non-Redfieldian carbon model for the Baltic Sea (ERGOM version 1.2) – implementation and budget estimates.“ Geoscientific Model Development 15, 8473–8540. https://doi.org/10.5194/gmd-15-8473-2022
A.K. Wittenborn, H. Radtke, C. Dutheil, H.W. Arz, J. Kaiser, 2022. „A downcore calibration of the TEX86L temperature proxy for the Baltic Sea.“ Continental Shelf Research 251, 104875. https://doi.org/10.1016/j.csr.2022.104875
2021
T.P. Bauer, P. Holtermann, B. Heinold, H. Radtke, O. Knoth, K. Klingbeil, 2021. „ICONGETM v1.0 – flexible NUOPC-driven two-way coupling via ESMF exchange grids between the unstructured-grid atmosphere model ICON and the structured-grid coastal ocean model GETM.“ Geoscientific Model Development 14, 4843–4863. https://doi.org/10.5194/gmd-14-4843-2021
G. Schernewski, H. Radtke, R. Hauk, C. Baresel, M. Olshammar, S. Oberbeckmann, 2021. „Urban Microplastics Emissions: Effectiveness of Retention Measures and Consequences for the Baltic Sea.“ Frontiers in Marine Science 8.
G. Schernewski, H. Radtke, E. Robbe, M. Haseler, R. Hauk, L. Meyer, S. Piehl, J. Riedel, M. Labrenz, 2021. „Emission, Transport, and Deposition of visible Plastics in an Estuary and the Baltic Sea—a Monitoring and Modeling Approach.“ Environmental Management 68, 860–881. https://doi.org/10.1007/s00267-021-01534-2
2020
R. D. Osinski, K. Enders, U. Gräwe, K. Klingbeil, and H. Radtke. „Model uncertainties of a storm and their influence on microplastics and sediment transport in the Baltic Sea“. Ocean Science 16, 1491–1507, 2020.
H. Radtke, S.-E. Brunnabend, U. Gräwe, and H. E. M. Meier. „Explaining interdecadal salinity changes in the Baltic Sea in a 1850-2008 hindcast simulation“. Climate of the Past 16, 1617–1642, 2020.
G. Schernewski, H. Radtke, R. Hauk, C. Baresel, M. Olshammar, R. D. Osinski, S. Oberbeckmann. „Transport and behavior of microplastics emissions from urban sources in the Baltic Sea“. Frontiers in Environmental Science, section Toxicology, Pollution and the Environment.
M. Gogina, M.L. Zettler, I. Wåhlström, H. Andersson, H. Radtke, I. Kuznetsov, and B.R. MacKenzie. „A combination of species distribution and ocean-biogeochemical models suggests that climate change overrides eutrophication as the driver of future distributions of a key benthic crustacean in the estuarine ecosystem of the Baltic Sea“. ICES Journal of Marine Science, fsaa107.
R. D. Osinski and H. Radtke. „Ensemble hindcasting of wind and wave conditions with WRF and Wavewatch III® driven by ERA5“. Ocean Science 16, 355-371.
A. Graiff, U. Karsten, H. Radtke, M. Wahl, and A. Eggert. „Model simulation of seasonal growth of Fucus vesiculosus in its benthic community“. Limnology and Oceanography: Methods, 2020.
D. Neumann, M. Karl, H. Radtke, V. Matthias, R. Friedland and T. Neumann. „Quantifying the contribution of shipping NOx emissions to the marine nitrogen inventory – a case study for the western Baltic Sea“. Ocean Science, 16, 115–134, 2020
2019
H.E.M. Meier, C. Dieterich, K. Eilola, M. Gröger, A. Höglund, H. Radtke, S. Saraiva, and I. Wåhlström. „Future projections of record-breaking sea surface temperature and cyanobacteria bloom events in the Baltic Sea“. Ambio, 2019.
M. Kniebusch, H.E.M. Meier and H. Radtke. „Changing Salinity Gradients in the Baltic Sea As a Consequence of Altered Freshwater Budgets“. Geophysical Research Letters, 46, 9739-9747. 2019.
H. Radtke, F. Börgel, S.-E. Brunnabend, A. Eggert, M. Kniebusch, H.E.M. Meier, D. Neumann, T. Neumann, and M. Placke. „Validator – a Web-Based Interactive Tool for Validation of Ocean Models at Oceanographic Stations“. Journal of Open Research Software 7, 18. 2019.
H. Radtke, M. Lipka, D. Bunke, C. Morys, J. Woelfel, B. Cahill, M.E. Böttcher, S. Forster, T. Leipe, G. Rehder, T. Neumann. „Ecological ReGional Ocean Model with vertically resolved sediments (ERGOM SED 1.0): coupling benthic and pelagic biogeochemistry of the south-western Baltic Sea“. Geoscientific Model Development 12, 275–320. 2019.
2018
T. Leipe, M. Naumann, F. Tauber, H. Radtke, R. Friedland, A. Hiller, and H. W. Arz. „Regional Distribution Patterns of Chemical Parameters in Surface Sediments of the South-Western Baltic Sea and Their Possible Causes“. Geo-Marine Letters 37 (6): 593–606, 2018.
M. Maar, M. Butenschön, U. Daewel, A. Eggert, W. Fan, S.S. Hjøllo, M. Hufnagl, M. Huret, R. Ji, G. Lacroix, M.A. Peck, H. Radtke, S. Sailley, M. Sinerchia, M.D. Skogen, M. Travers-Trolet, T.A. Troost, and K. van de Wolfshaar, “Responses of summer phytoplankton biomass to changes in top-down forcing: Insights from comparative modelling,” Ecological Modelling, vol. 376, pp. 54–67, 2018.
2017
A. Graiff, A. Eggert, H. Radtke, U. Karsten, and M. Wahl, “Modelling the Seasonal Growth of the Brown Seaweed Fucus Vesiculosus in the Kiel Outdoor Benthocosms,“ Phycologia, vol. 56, pp. 67–68, 2017.
T. Neumann, H. Radtke, and T. Seifert, “On the Importance of Major Baltic Inflows for Oxygenation of the Central Baltic Sea,” J. Geophys. Res. – Oceans, vol. 122, no. 2, pp. 1090–1101, 2017.
A. Allin, G. Schernewski, R. Friedland, T. Neumann, and H. Radtke, “Climate Change Effects on Denitrification and Associated Avoidance Costs in Three Baltic River Basin - Coastal Sea Systems,” Journal of Coastal Conservation vol. 21, no. 4, pp. 561–69, 2017.
2016
H. Radtke and M. Maar, “Estimating the effective nitrogen import: An example for the North Sea – Baltic Sea boundary,” J. Geophys. Res. - Biogeosciences, 121, 2016
2015
H. Radtke and H. Burchard, “A positive and multi-element conserving time stepping scheme for biogeochemical processes in marine ecosystem models,” Ocean Modelling, vol. 85, pp. 32–41, 2015.
2013
H. Radtke, T. Neumann, and W. Fennel, “A Eulerian nutrient to fish model of the Baltic Sea — A feasibility-study,” Journal of Marine Systems, vol. 125, pp. 61–76, 2013.
J. Carstensen, J. Andersen, K. M. Dromph, V. Flemming-Lehtinen, S. Simis, B. Gustafsson, A. Norkko, H. Radtke, D. L. J. Petersen, and T. Uhrenholdt, “Approaches and methods for eutrophication target setting in the Baltic Sea region,” Helsinki Commission-HELCOM, 2013.
2012
H. Radtke, T. Neumann, M. Voss, and W. Fennel, “Modeling pathways of riverine nitrogen and phosphorus in the Baltic Sea,” J. Geophys. Res. - Oceans, vol. 117, no. C9, p. C09024, 2012.
H. Radtke, “Einfluss biologischer Prozesse auf die Ausbreitungswege von Nährstoffen in der Ostsee,” Universität Rostock, Mathematisch-Naturwissenschaftliche Fakultät, Dissertation, 2012.
2010
W. Fennel, H. Radtke, M. Schmidt, and T. Neumann, “Transient upwelling in the central Baltic Sea,” Continental Shelf Research, vol. 30, no. 19, pp. 2015–2026, 2010.
Working group