GSFS Faculty

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Kodaira Tsubasa

(Lecturer/Assistant Professor/Division of Environmental Studies)

Department of Ocean Technology, Policy, and Environment/Ocean Environment Group/Digital Twin of Ocean、Autonomous Distributed Ocean Observation、Sea Ice as a Driver of Climate Change

Career Summary

Education
March 24, 2009 B.E., Department of Systems Innovation, Faculty of Engineering, The University of Tokyo (Course in Environmental and Energy Systems)
March 22, 2011 M.S., Department of Ocean Technology, Policy, and Environment, Graduate School of Frontier Sciences, The University of Tokyo
March 24, 2014 Ph.D., Department of Ocean Technology, Policy, and Environment, Graduate School of Frontier Sciences, The University of Tokyo (Doctor of Environmental Studies)

Professional Experience
April 1, 2011 – March 31, 2014 Research Fellow (DC1), Japan Society for the Promotion of Science (JSPS)
April 1, 2014 – April 30, 2014 Project Researcher, Graduate School of Frontier Sciences, The University of Tokyo
May 1, 2014 – October 31, 2016 Postdoctoral Research Fellow, Dalhousie University, Canada
November 1, 2016 – August 30, 2021 Assistant Professor, Graduate School of Frontier Sciences, The University of Tokyo
September 1, 2021 – Present Lecturer, Graduate School of Frontier Sciences, The University of Tokyo

Educational Activities

Graduate School (Department of Ocean Technology, Policy, and Environment): Ocean Data Science, Fundamentals of Meteorology and Oceanography, Ocean Technology, Polici, and Environment Project I, II Undergraduate (Faculty of Engineering): Mechanics Exercises IA / IIA, Fluid Mechanics Exercises A1, Basic Project, Applied Project, Interdisciplinary Project, Fundamentals of Modern Engineering I

Research Activities

1) Development of Ocean Models to Support Marine Development and Conservation
Sustainable marine development and conservation require reconstructing and understanding the ocean environment from limited information. The most comprehensive ocean information is provided by reanalysis data products, which integrate observations and numerical models through data assimilation techniques. However, their spatial resolution is typically limited to around 10 km, which is insufficient for analyzing activities in specific regions. We are working on the development of ocean models that can generate high-resolution ocean information for any target area.

2) Drastic Increase in Ocean Information through Autonomous Distributed Observation
Although approximately 4,000 Argo floats currently operate as part of the global near-real-time ocean observation network, observations are still limited to roughly one point per several hundred kilometers, and coverage remains especially sparse in polar regions due to sea ice. We aim to construct a system capable of autonomously and distributively collecting ocean data, drastically increasing the volume and resolution of ocean information. This effort will support the sustainable use of the ocean—including offshore wind power, blue carbon, and polar marine environments.

3) Sea Ice, Submesoscale Eddies, and Internal Waves as Drivers of Climate Change
While the rapid decline in summer Arctic sea ice extent is considered a clear sign of global warming, the underlying melt processes remain insufficiently understood. Focusing on episodes of rapid ice melt observed under strong wind conditions during the melting season, we aim to elucidate and model the mechanisms involved. These findings will contribute to improving short- and medium-term sea ice forecasts and ultimately support the utilization of Arctic shipping routes, which are expected to play a role in global decarbonization.

Literature

  1. Yasushi Fujiwara, Takuji Waseda, Tsubasa Kodaira, Takehiko Nose, Tomotaka Katsuno, Koya Sato, 2025: Ice particle grouping under waves: Experimental investigation of the initial stage of pancake ice formation. Cold Regions Science and Technology, 233, 104449.
  2. Eiji Watanabe, Hiromichi Ueno, Tsubasa Kodaira, Akihiko Murata, Shigeto Nishino, Takahito Ikenoue, Masanobu Yamamoto, Daiki Nomura, Hiroto Abe, Yusuke Kawaguchi, Daisuke Hirano, Yuanxin Zhang, Sayaka Yasunaka, 2025: Arctic marine environments regulated by ocean transport and air–sea–land interaction: Findings from the ArCS II Ocean Research Program. Polar Science, 101205.
  3. Takehiko Nose, Tomotaka Katsuno, Takuji Waseda, Shuki Ushio, Jean Rabault, Tsubasa Kodaira, Joey Voermans, 2023: Observation of wave propagation over 1,000 km into Antarctica winter pack ice. Coastal Engineering Journal, 1–17.
  4. Tsubasa Kodaira, Tomotaka Katsuno, Takehiko Nose, Motoyo Itoh, Jean Rabault, Mario Hoppmann, Masafumi Kimizuka, Takuji Waseda, 2023: An affordable and customizable wave buoy for the study of wave-ice interactions: design concept and results from field deployments. Coastal Engineering Journal, 1–15.
  5. Takehiko Nose, Jean Rabault, Takuji Waseda, Tsubasa Kodaira, Yasushi Fujiwara, Tomotaka Katsuno, Naoya Kanna, Kazutaka Tateyama, Joey Voermans, Tatiana Alekseeva, 2023: A comparison of an operational wave–ice model product and drifting wave buoy observation in the central Arctic Ocean. Polar Research, 42.
  6. Tsubasa Kodaira, Kaushik Sasmal, Rei Miratsu, Tsutomu Fukui, Tingyao Zhu, Takuji Waseda, 2023: Uncertainty in wave hindcasts in the North Atlantic Ocean. Marine Structures, 89, 103370.
  7. Rei Miratsu, Kaushik Sasmal, Tsubasa Kodaira, Tsutomu Fukui, Tingyao Zhu, Takuji Waseda, 2022: Evaluation of ship operational effect based on long-term encountered sea states using wave hindcast combined with storm avoidance model. Marine Structures, 86, 103293.
  8. Takuji Waseda, Alberto Alberello, Takehiko Nose, Takenobu Toyota, Tsubasa Kodaira, Yasushi Fujiwara, 2022: Observation of anomalous spectral downshifting of waves in the Okhotsk Sea Marginal Ice Zone. Philosophical Transactions of the Royal Society A, 380(2235).
  9. Pengcheng Wang, Natacha B. Bernier, Keith R. Thompson, Tsubasa Kodaira, 2021: Evaluation of a global total water level model in the presence of radiational S2 tide. Ocean Modelling, 168, 101893.
  10. Kaushik Sasmal, Rei Miratsu, Tsubasa Kodaira, Tsutomu Fukui, Tingyao Zhu, Takuji Waseda, 2021: Statistical model representing storm avoidance by merchant ships in the North Atlantic Ocean. Ocean Engineering, 235, 109163.
  11. Joey J. Voermans, Qingxiang Liu, Aleksey Marchenko, Jean Rabault, Kirill Filchuk, Ivan Ryzhov, Petra Heil, Takuji Waseda, Takehiko Nose, Tsubasa Kodaira, Jingkai Li, Alexander V. Babanin, 2021: Wave dispersion and dissipation in landfast ice: comparison of observations against models. [Journal name missing]
  12. Takuji Waseda, Shogo Watanabe, Wataru Fujimoto, Takehiko Nose, Tsubasa Kodaira, Amin Chabchoub, 2021: Directional Coherent Wave Group From an Assimilated Non-linear Wavefield. Frontiers in Physics, 9.
  13. Takuji Waseda, Takehiko Nose, Tsubasa Kodaira, Kaushik Sasmal, Adrean Webb, 2020: Climatic trends of extreme wave events caused by Arctic Cyclones in the western Arctic Ocean. Polar Science, 100625.
  14. Tsubasa Kodaira, Takuji Waseda, Takehiko Nose, Jun Inoue, 2020: Record high Pacific Arctic seawater temperatures and delayed sea ice advance in response to episodic atmospheric blocking. Scientific Reports, 10(1).
  15. Takehiko Nose, Takuji Waseda, Tsubasa Kodaira, Jun Inoue, 2020: On the coagulated pancake ice formation: Observation in the refreezing Chukchi Sea and comparison to the Antarctic consolidated pancake ice. Polar Science, 27, 100622.
  16. Tsubasa Kodaira, Takuji Waseda, Takehiko Nose, Kazutoshi Sato, Jun Inoue, Joey Voermans, Alexander Babanin, 2020: Observation of on-ice wind waves under grease ice in the western Arctic Ocean. Polar Science, 27, 100567.
  17. Takehiko Nose, Takuji Waseda, Tsubasa Kodaira, Jun Inoue, 2020: Satellite-retrieved sea ice concentration uncertainty and its effect on modelling wave evolution in marginal ice zones. The Cryosphere, 14(6), 2029–2052.
  18. Tsubasa Kodaira, Takuji Waseda, 2019: Tidally generated island wakes and surface water cooling over Izu Ridge. Ocean Dynamics, 69(11–12), 1373–1385.
  19. John T. Imamura, Ken Takagi, Takuji Waseda, Tsubasa Kodaira, 2019: Comparison of Numerical Simulations and Field Measurements of Current Flow in the Tokara Strait. OCEANS 2018 MTS/IEEE Charleston.
  20. Shogo Watanabe, Wataru Fujimoto, Tak Nose, Tsubasa Kodaira, Graham Davies, Daniel Lechner, Takuji Waseda, 2019: Data assimilation of the stereo reconstructed wave fields to a nonlinear phase resolved wave model. OMAE Proceedings, Vol. 9.
  21. Tsubasa Kodaira, Ryota Wada, Daimon Wada, Shogo Watanabe, Yuki Kita, Takuji Waseda, 2019: Development and Demonstration of a Low-Cost Coastal Wind Observation System. Journal of the Japan Society of Naval Architects and Ocean Engineers, 29, 163–169.
  22. Yu-Lin K. Chang, Yasumasa Miyazawa, Tsubasa Kodaira, Swadhin Behera, 2018: Philippines–Taiwan Oscillations and its connection to tropical cyclone frequency in the western North Pacific Ocean. Scientific Reports, 8(1).
  23. Tsubasa Kodaira, Takuji Waseda, 2018: ADCP observation and numerical model prediction of tidal currents near Kozu Island. OMAE Proceedings, Vol. 10.
  24. Yu-Lin Chang, Yasumasa Miyazawa, Lie-Yauw Oey, Tsubasa Kodaira, Shihming Huang, 2017: The formation processes of phytoplankton growth and decline in mesoscale eddies in the western North Pacific Ocean. Journal of Geophysical Research: Oceans, 122(5), 4444–4455.
  25. 小平 翼, 和田 良太, 早稲田 卓爾, 2017: 日本沿岸潮流発電の資源量推定に対する潮流の長期変動の影響. 日本船舶海洋工学会論文集, 25, 151–156.
  26. Tsubasa Kodaira, Keith R. Thompson, Natacha B. Bernier, 2016: The effect of density stratification on the prediction of global storm surges. Ocean Dynamics, 66(12), 1733–1743.
  27. Tsubasa Kodaira, Takuji Waseda, Motoyasu Miyata, Wooyoung Choi, 2016: Internal solitary waves in a two-fluid system with a free surface. Journal of Fluid Mechanics, 804, 201–223.
  28. Tsubasa Kodaira, Keith R. Thompson, Natacha B. Bernier, 2016: Prediction of M2 tidal surface currents by a global baroclinic ocean model and evaluation using observed drifter trajectories. Journal of Geophysical Research: Oceans, 121(8), 6159–6183.
  29. K. Kiyomatsu, Y. Kadomoto, T. Kodaira, T. Waseda, K. Takagi, S. M. Verlamov, Y. Miyazawa, 2015: ADCP measurements of ocean currents near Miyake island for a Kuroshio energy converter development project. RENEW 2014, 161–168.
  30. Tsubasa Kodaira, Takuji Waseda, Yasumasa Miyazawa, 2014: Nonlinear internal waves generated and trapped upstream of islands in the Kuroshio. Geophysical Research Letters, 41(14), 5091–5098.
  31. 清松 啓司, 小平 翼, 門元 之郎, 早稲田 卓爾, 高木 健, 2014: 三宅島近海流況観測とそれに基づく海流エネルギー資源量推定. 日本船舶海洋工学会論文集, 20, 147–155.
  32. Tsubasa Kodaira, Takuji Waseda, Tetsuji Nakagawa, Osamu Isoguchi, Yasumasa Miyazawa, 2013: Measuring the Kuroshio Current Around Miyake Island, a Potential Site for Ocean-Current Power Generation. International Journal of Offshore and Polar Engineering, 23(4), 272–278.

Other Activities

Development of an Ocean Digital Twin for a Decarbonized Society
We aim to develop an ocean digital twin that integrates high-precision observations and numerical models to reproduce and forecast the marine environment, while also consolidating related datasets to support decision-making for sustainable ocean development and the implementation of ocean-based decarbonization technologies. Our approach goes beyond numerical ocean modeling by emphasizing the integration and practical use of related ocean data, thereby contributing to the promotion of marine renewable energy and advancements in blue carbon strategies.

Future Plan

We aim to develop an ocean digital twin that supports informed decision-making toward sustainable ocean development.

Messages to Students

I believe graduate school should be a place where you take the first step, engage consistently, and build confidence in yourself.

URL

http://www.orca.k.u-tokyo.ac.jp/WasedaLab/

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