JAMSTEC > Basic Research Area  > Department of Mathematical Science and Advanced Technology(MAT) > Member > Takashi Nakagawa

Department of Mathematical Science and Advanced Technology (MAT)

Members

Takashi Nakagawa

photo

Senior Scientist
Japan Agency for Marine-Earth Science and Technology
Department of Mathematical Science and Advanced Technology

3173-25, Showa-machi, Kanazawa-ku, Yokohama, Kanagawa, 236-0001, Japan
ntakashi_at_jamstec.go.jp


Short CV

Employment

2002.7 - 2003.10 Postdoctoral Researcher, UCLA, USA
2003.11 - 2004.7 Research Associate, Univ. of Chicago, USA
2004.9 - 2007.3 Postdoctoral Fellow, Univ. of Tokyo, Japan
2007.4 - 2008.12 Assistant Professor, Kyushu University, Japan
2009.1 - 2011.3 Senior Research Associate, ETH Zurich, Switzerland
2011.4 - 2013.3 Scientist, JAMSTEC, Japan
2013.4 - present Senior Scientist, JAMSTEC, Japan

Education

1997.4 - 1999.3 M.S. Degree, Univ. of Tokyo, Japan
1999.4 - 2002.5 Ph. D. Degree, Univ. of Tokyo, Japan

Research Topics

Research Interest: Geophysical Fluid Dynamics and Geodynamics
1. Core-mantle coupled evolution
We develop a coupled core-mantle evolution model based on thermo-chemical multiphase mantle convection and global heat balance in thermodynamic energetics for core alloy. To use this model, we reveal the thermo-chemical evolution processes from early Earth to present Earth with constraints on geological, geochemical, geophysical and mineral physics.
core_evo
Thermal and magnetic evolution of Earth's core in a coupled core-mantle evolution model.

2. The origin of deep mantle heterogeneity
We incorporate realistic phase diagram databases derived from Gibbs free energy minimization into numerical thermo-chemical multiphase mantle convection simulations. The advantage for this type of model is to calculate elastic properties of mantle minerals in mantle dynamics and to evaluate what global tomographic images stand for the mantle dynamic. As a result, we can discuss the origin of deep mantle heterogeneity that would be generated from thermo-chemical origin.
seismic anomalies
Thermo-chemical structure (top); Vs and bulk sound velocity anomalies (bottom)

3. Geodynamo with thermo-chemical structure of Earth's core
In order to examine the magnetic field by dynamo actions with thermo-chemical structure of Earth's core obtained from seismic analyses, we use numerical dynamo simulations in a rotating spherical shell including a stably stratified region. Revealing the origin of such a structure, we attempt wide-parameter range modeling for dynamo solutions that are characterized as strong field, weak field and failed solution. As a result of this wide parameter range survey, the origin of seismic structure in Earth's core would be caused by the compositional origin, in terms of the light element release due to the inner core growth.
geodynamo
Radial magnetic field at CMB. Left: Unstratified; Right: Stratified.

4. Global-scale water circulation in mantle dynamics
The surface ocean is covered with 70 % of Earth’s surface. Due to ocean floor dynamics such as subductions, the sea-water can be transported into deep Earth’s interior. This would be suggested from geochemical and high P-T experiments. The database on maximum water content of hydrous mantle minerals obtained from compilations of experimental data can be directly incorporated into numerical mantle convection simulations. As a result of numerical simulations of mantle dynamics with hydrous minerals, the water content in deep mantle is strongly regulated by effects of dehydration process of aquarius fluid in the mantle minerals. However, the hydrous oceanic crust may enhance the activity of surface plate motion due to lubrication. Because of that, the heat transfer across the hydrous mantle may also enhance ~30 % compared to that across the dry mantle. This is quite different from predictions provided from simple parameterized theory thus this implies that non-linearity on dehydration and rheological properties caused by hydrous mantle minerals is strongly influenced for the thermo-chemical-hydrous evolution of Earth’s deep interior as well as ocean-atmospheric evolution.
geodynamo
Thermo-chemical-viscous-hydrous structures in Earth’s mantle as a function of viscosity dependence of water.

Publications

Selected Publications (Peer-Reviewed)

  • Nakagawa, T., and P. J. Tackley, Lateral variation of CMB heat flux and deep mantle seismic velocity caused by a thermal-chemical-phase boundary layer in 3D spherical shell, Earth Planet. Sci. Lett., 271, 348-358, 2008.
  • Nakagawa, T., and P. J. Tackley, Influence of initial CMB temperature and other parameters on the thermal evolution of Earth's core resulting from thermo-chemical mantle convection, G-cubed, 10, Q03004, doi:10.1029/2010GC003031, 2010.
  • Nakagawa, T., P. J. Tackley, F. Deschamps, and J. A. D. Connolly, Radial 1-D seismic structures in the deep mantle in mantle convection simulations with self-consistently calculated mineralogy, G-cubed, 13, Q11002, doi:10.1029/2012/GC004325, 2012.
  • Nakagawa, T., and P. J. Tackley, Implications for high core thermal conductivity on Earth's coupled core-mantle evolution, Geophys. Res. Lett., 40, doi:10.1002/grl.50574, 2013.
  • Nakagawa, T., and P. J. Tackley, Influence of combined primordial layering and recycled MORB on the coupled thermal evolution of Earth's mantle and core, G-cubed, 15, 10.1002/2013GC005128, 2014.
  • Nakagawa, T., An implication for the origin of stratification below the core-mantle boundary region in numerical dynamo simulations in a rotating spherical shell, Phys. Earth Planet. Int., doi: 10.1016/j.pepi.2015.02.007, 2015.
  • Nakagawa, T., T. Nakakuki, and H. Iwamori, Water circulation and global mantle dynamics: Insight from numerical modeling, G-cubed.,2015, accepted.