The ex-GP-EES student Ryohei Yamaguchi and the program director Prof. Toshio Suga analyzed data as great a spatial and temporal coverage as possible and found the statistically significant strengthening of of the upper-ocean thermal stratification as a consequence of global warming.

This research result was published in Journal of Geophysical Research: Oceans.
https://doi.org/10.1029/2019JC015439

Title: Trend and Variability in global upper-ocean stratification since the 1960s
Authors: Ryohei Yamaguchi1,2 and Toshio Suga1
1 Department of Earth Science, Graduate School of Science, Tohoku University, Japan
2 Center for Climate Physics, Institute for Basic Science, Busan, South Korea