Japan Geoscience Union Meeting 2019

Presentation information

[E] Poster

A (Atmospheric and Hydrospheric Sciences ) » A-OS Ocean Sciences & Ocean Environment

[A-OS09] Ocean Mixing Processes: Impact on Biogeochemistry, Climate and Ecosystem

Sun. May 26, 2019 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Ichiro Yasuda(Atmosphere and Ocean Research Institute, The University of Tokyo), Toshiyuki Hibiya(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Jun Nishioka(Hokkaido University, Institute of low temperature sciences), Shin-ichi Ito(Atmosphere and Ocean Research Institute, The University of Tokyo)

[AOS09-P06] The effect of 18.6-year period lunar nodal cycle on Pacific Decadal Oscillation (PDO)

*Masaki Hamamoto1, Ichiro Yasuda1 (1.Atmosphere and Ocean Research Institute, The University of Tokyo)

Keywords:18.6-year period lunar nodal cycle, Pacific Decadal Oscillation

Pacific Decadal Oscillation (PDO) is the most dominant decadal-inter-decadal ocean-climate variability over the North Pacific; however, the periodicity and cause have not been fully understood. Previous studies suggested that 18.6-year period lunar tidal cycle (T18.6) regulate bi-decadal PDO variability through changes in the strength of diapycnal mixing of ocean around the Kuril Islands to result in ocean variability, together with air-sea interactions in the mid-latitude North Pacific and/or equatorial Pacific. In the present study, 297yr-long reconstructed PDO timeseries was re-examined, and 27.9yr (3/2 times 18.6-yr, henceforth, T27.9) period variability was significantly detected, and the zero-crossing from minus to plus was found to occur simultaneously with T18.6 variability in the interval of 55.4 years (3 times T18.6). In the PDO spectrum, a broad multi-decadal 50-80-yr peak (corresponding to 3-5 times T18.6, henceforth TM) was also detected with the zero-crossing synchronized with T18.6; this is the extension of previous studies during 1900-2000 back to 1700s on the synchronous changes of bi-decadal and penta-decadal variabilities. These T18.6, T27.9 and TM explain 71% of the 10-year low-passed PDO variability. These imply that the 27.9-yr and the multi-decadal variabilities could be related to T18.6 tide-induced variability, and may be excited by T18.6 tidal forcing, considering that external periodic forcing for delayed oscillator models could excite 3 times period of the external forcing and some non-linear processes may make the half-period variability.