Origin of North Pacific Bidecadal Oscillation and Influence of Tidal 18.6-year Modulation

Research summary

　It is proposed that a remarkable 20-year oscillation, the bidecadal oscillation, exists in the atmosphere and the ocean in the North Pacific. However, the mechanism of the bidecadal oscillation, especially in the atmosphere, is an unsolved problem. The major hypotheses are 1) the hypothesis of 18.6-year ocean tidal mixing modulation and its influence and 2) the delayed oscillation hypothesis, for both of which the feedback from the ocean to the atmosphere is important, and 3) the climate noise hypothesis that does not require ocean-to-atmosphere feedback. Therefore, this study will address the question what is the origin of the North Pacific Bidecadal Oscillation, with emphases on the contribution from the ocean to the atmosphere and the teleconnections. To this end, I will analyze the state-of-the-art large ensemble experiment of an atmospheric general circulation model.

　For the ocean variability, on the other hand, it has been reported that the tidal 18.6-year modulation affects the dissolved oxygen in the western subarctic North Pacific Ocean and in the Bering Sea, but analyses were limited to these specific areas. It is unknown whether or not the 18.6-year tidal modulation influence dissolved oxygen variability in other regions. Therefore, I will comprehensively analyze the dissolved oxygen fluctuation by using my own gridded oxygen dataset.

　As a whole, this research aims to contribute better understanding of climate, ocean and ecosystem related to the North Pacific Bidecadal Oscillation and 18.6-years tidal mixing modulation.

Principal Investigator：Shoshiro MINOBE1,2,
1. Faculty of Science, Hokkaido University
2. Graduate School of Science, Hokkaido University
https://www.sci.hokudai.ac.jp/grp/poc/top/

Collaborator：Yumi Abe, School of Science, Hokkaido University