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Dr. Takasumi Kurahashi-Nakamura



Geosystem Modeling


+49 421 218-65438


+49 421 218-65438



GEO, 5500

Takasumi Kurahashi-Nakamura


Understanding the role of marine biogeochemical processes in the climate changes during the glacial-interglacial cycles (with CESM)

It is well known that carbon dioxide concentration (CO2 level, hereafter) in the atmosphere has been increasing since the industrial revolution due to human’s CO2 emission. Our life in the future can suffer from climate changes induced by the increase in the CO2 level and/or from the CO2 increase itself (e.g., ocean acidification). To project the history of the CO2 level in the future, it is essential to understand the controlling mechanisms of the CO2 level in the climate system. The glacial-interglacial cycles in the last 100 kys are considered to be one of the most qualified research targets for that purpose, because they demonstrate historical (natural) climate changes with large variations in CO2-level.

It is widely considered that the marine carbon cycle would have had a large influence on the CO2-level variations in the glacial-interglacial cycles. However, the dynamics are not well-understood yet. I will tackle this issue by focusing on the budget of calcium carbonate (CaCO3) in the ocean by which the chemical condition (e.g., pH) of the entire ocean, and thus the atmospheric CO2 level, should be changed. Using a realistic ocean model including biogeochemical processes coupled with a sediment model will enable us to evaluate impacts of CaCO3 budget on the global climate, and to compare model results directly with corresponding geological evidence taken from seafloor sediments.


Reconstruction of LGM ocean circulation with a data assimilation technique (the adjoint method with MITgcm).

Understanding the behavior of the Earth's climate system under different conditions in the past is the basis for robust projections of future climate changes. It is believed that the ocean circulation plays a very important role in the climate system, because it can greatly affect climate in dynamical-thermodynamical ways (as a medium of heat transport) and in biogeochemical ways (by modifying the marine carbon cycle). In this context, studying the period of the Last Glacial Maximum (LGM) is particularly important, because it represents a climate state that is very different from today. However, the ocean circulation during the LGM is still uncertain.

Please also see the Project OC1 page.


03/2004Ph.D."Evolution of the Surface Environment of Mars: Numerical Studies on the Climate System", Department of Earth and Planetary Science, University of Tokyo.
03/2001M.Sc.Department of Earth and Planetary Science, University of Tokyo.
03/1999B.Sc.Department of Geological Science, University of Tokyo.


05/2015 -
Postdoctoral Fellow, Jacobs University Bremen.
01/2010 - presentResearcher, MARUM, Bremen University.
06/2008 - 10/2009Visiting Fellow, School of Geographical Sciences, University of Bristol.
04/2008 - 12/2009Japan Society for the Promotion of Science (JSPS) Research fellow, Center fo Climate System Research, University of Tokyo.
04/2004 - 03/2008Postdoctoral researcher, Frontier Research Center for Global Change, JAMSTEC.
04/2001 - 03/2004Japan Society for the Promotion of Science (JSPS) Research fellow, Department of Earth and Planetary Science, University of Tokyo.


Numerical modeling of complex systems is an instructive and useful method to describe, comprehend, and predict the behaviors of such systems in a quantitative way. The consistent and general motive of my research is interest in numerical modelling of natural phenomena, and of social phenomena as well.

In natural science, my focus is on climate stability (or variability) and habitability of terrestrial planets, on the dynamics of the climate system (e.g., feedbacks among the subsystems), and on how to combine knowledge from numerical models and that from observation. To tackle these problems, I have been working in various interdisciplinary research fields with various numerical models. In particular, I have been interested in the dynamics to determine the amount of CO2 in the atmosphere because CO2 is an important greenhouse gas species to control the surface environment of the Earth and Mars.

In the field of social science, dynamics of people’s opinion in a society is a major concern, for example, from the political-science viewpoint, because it is expected that it is strategically important to understand how majorities are formed, how many majorities are created, and how stable they are. Analyzing social dynamics with a simplified numerical model is important for general understanding of phenomena, for well-controllable plenty of experiments, and for giving reasonable ideas to design more realistic prediction models in the future.

Specific research interests of mine includes/included:

  • Mechanisms to control atmospheric CO2 level in the glacial-interglacial period.
  • The role of marine carbon cycles in climate changes in the past and future.
  • General understanding the behaviour of the climate system (e.g., intrinsic feedbacks)
  • Regulating mechanisms of the long-timescale evolution of climate of Mars.
  • Opnion dynamics with agent-based modelling


Kurahashi-Nakamura, Takasumi, A. Paul, G. Munhoven, U. Merkel, and M. Schulz, "Coupling of a sediment diagenesis model (MEDUSA) and an Earth system model (CESM1.2): a contribution toward enhanced marine biogeochemical modelling and long-term climate simulations", Geosci. Model Dev., 13, 825–840, https://doi.org/10.5194/gmd-13-825-2020, 2020.

Breitkreuz, C., A. Paul, T. Kurahashi‐Nakamura, M. Losch, and M. Schulz, "A dynamical reconstruction of the global monthly‐mean oxygen isotopic composition of seawater", J. Geophys. Res. Oceans, https://doi.org/10.1029/2018JC014300, 2018.

Kurahashi-Nakamura, Takasumi, A. Paul, and M. Losch, "Dynamical reconstruction of the global ocean state during the Last Glacial Maximum", Paleoceanography, 32, doi:10.1002/2016PA003001, 2017.

Kurahashi-Nakamura, Takasumi, M. Losch, and A. Paul, "Can sparse proxy data constrain the strength of the Atlantic meridional overturning circulation?", Geosci. Model Dev., 7, 419-432, doi:10.5194/gmd-7-419-2014, 2014.

Kurahashi-Nakamura, Takasumi, A. Abe-Ouchi, and Y. Yamanaka, “Effects of physical changes in the ocean on atmospheric pCO2 during the last glacial maximum", Clim. Dyn., DOI10.1007/s00382-009-0609-5, 2010.

Kurahashi-Nakamura, Takasumi, A. Abe-Ouchi, Y. Yamanaka and K. Misumi, “Compound effects of Antarctic sea ice on atmospheric pCO2 change during glacial–interglacial cycle", Geophys. Res. Lett., 34, L20708, doi:10.1029/2007GL030898, 2007.

Kurahashi-Nakamura, Takasumi, and E. Tajika, “Atmospheric collapse and transport of carbon dioxide into the subsurface on early Mars”, Geophys. Res. Lett., 33, L18205, doi:10.1029/2006GL027170, 2006.

Kurahashi-Nakamura, Takasumi, and E. Tajika, “Evolution of the Martian climate: effects of the ice sheets”, Seppyo, Journal of the Japanese Society of Snow and Ice, Vol. 67, No. 2, pp.133-145, 2005 (in Japanese).

Nakamura, Takasumi, and E. Tajika, “Climate change of Mars-like planets due to obliquity variations: implications for Mars”, Geophys. Res. Lett., 30, No. 13, 1685, doi:10.1029/2002GL016725, 2003.

Nakamura, Takasumi, and E. Tajika, “Stability of the Martian climate system under the seasonal change condition of solar radiation”, Journal of Geophysical Research, vol.107, no.E11, 5094, doi:10.1029/2001JE001561, 2002.

Nakamura, Takasumi, and E. Tajika, “The Martian Climate System : Its Stability and Evolution”, Planetary People, Journal of the Japanese Society for Planetary Science, vol.10, no.4, pp.192-201, 2001 (in Japanese).

Nakamura, Takasumi, and E. Tajika, “Stability and evolution of the climate system of Mars”, Earth, Planets, and Space, vol.53, pp.851-859, 2001.


Lorenz, Jan, T. Kurahashi-Nakamura, and S. Shikano, "Cycles of public policy mood through opinion dynamics under heterogeneous bounds of confidence" (in prep.).

Kurahashi-Nakamura, Takasumi, M. Mäs, and J. Lorenz, "Robust clustering in generalized bounded confidence models", Journal of Artificial Societies and Social Simulation, 19, (4), 7, DOI:10.18564/jasss.3220, 2016.