Session: 02-04-02 Probabilistic and Spectral Wave Modelling (Co-hosted with the Ian Young Honoring Symposium)

Paper Number: 104435

104435 - On Nonlinear Wave Evolution Under the Ice 

More than six decades have passed since the elementary theories of wind-generated waves were presented and those still form the foundation of wave forecast models. Recently, attention is given to wave evolution under sea ice. The retreat of sea ice in the summer Arctic Ocean permits wind waves to develop in the open waters. Up to this point, however, most studies dealt with attenuation, and not so much attention was given to wind pumping and nonlinear interaction in ice. We present recent observational results showing an anomalous spectral downshift that likely results from the combined effect of nonlinear interaction and dissipation.

 

In February 2020, two in-situ measurements were made in the Okhotsk Sea; one by a wave buoy on ice and the other by a stereo imaging system on board P/V Soya. They concurrently detected a wave system whose incoming wave peak frequency was around 10 s but rapidly downshifted to 15 s propagating through the MIZ. The lower-frequency wave energy grew at the expense of energy attenuation at high frequencies, indicating a possible nonlinear energy transfer. The rate of downshifting is equivalent to or even faster than that of the unidirectional random wave field under the action of quasi-resonant interaction and breaking energy dissipation. We, therefore, conjectured that the anomalous downshifting is due to dissipation-driven nonlinear interaction.

 

In this presentation, we will also introduce a possible case of dissipation-driven nonlinear downshifting observed in the Arctic and/or Antarctic oceans.

 

It is yet to be investigated whether such nonlinear evolution under attenuation leads to a formation of a coherent wave group or not.

Presenting Author: Takuji Waseda The University of Tokyo

Presenting Author Biography: Education

Doctor of Philosophy, Department of Mechanical and Environmental Engineering, Ocean Engineering Program, University of California at Santa Barbara, March 22, 1997
Dissertation: Laboratory study of wind- and mechanically-generated waves

Master of Engineering, Department of Mechanical and Environmental Engineering, Ocean Engineering Program, University of California at Santa Barbara, December 14, 1991

Bachelor in Engineering, The University of Tokyo, Department of Naval Architecture and Ocean Engineering, March 28, 1990

Academic Experience

Department Chair, Department of Ocean Technology Policy and Environment, Graduate School of Frontier Sciences, the University of Tokyo, April 1, 2020 – March 30, 2022

Course Chair, Environment & Energy Course, Department of Systems Innovation, School of Engineering, the University of Tokyo, April 1, 2019 - March 30, 2020

Department Chair, Department of Ocean Technology Policy and Environment, Graduate School of Frontier Sciences, the University of Tokyo, April 1, 2016 – March 30, 2017

Professor, Department of Ocean Technology Policy and Environment, Graduate School of Frontier Sciences, the University of Tokyo, June 1, 2015 – now

Associate Professor, Department of Ocean Technology Policy and Environment, Graduate School of Frontier Sciences, the University of Tokyo, April 1, 2008 – May 31, 2015

Associate Professor, Department of Environmental and Ocean Engineering, Faculty of Engineering, the University of Tokyo, April 1, 2004 – March 31, 2008

Visiting Researcher, Japan Agency for Marine and Earth Science and Technology, May 1, 2004 – now

Researcher, Frontier Research System for Global Change, Japan, October 1, 1997 – March 31, 2004
Researcher (joint appointment), International Pacific Research Center, SOEST, U. of Hawaii, HI, April 1, 1998 – March 31, 2004

Post Graduate Researcher, Department of Mechanical and Environmental Engineering, University of California at Santa Barbara, October 1, 1996 – September 30, 1997

Authors:

Takuji Waseda The University of Tokyo
Alberto Alberello University of East Anglia
Takehiko Nose The University of Tokyo
Takenobu Toyota Institute of Low Temperature Science
Tsubasa Koraira The University of Tokyo
Yasushi Fujiwara Low Temperature Lab, Hokkaido University