JpGU-AGU Joint Meeting 2020

Presentation information

[E] Poster

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

[A-OS24] Exploring new frontiers of oceanic mixing research in the next decade

convener:Toshiyuki Hibiya(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Ichiro Yasuda(Atmosphere and Ocean Research Institute, The University of Tokyo), Lakshmi Kantha(Aerospace Engineering Sciences, University of Colorado, Boulder, Colorado, USA)

[AOS24-P01] Synchronized interdecadal periodic variations behind regime shifts in Pacific Decadal Oscillation

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

Keywords:regime shift, Pacific Decadal Oscillation, phase-lock, 18.6-yr lunar nodal cycle

Interdecadal climate variability over the North Pacific is examined using a 298-yr (1700-1997) Pacific Decadal Oscillation (PDO) index reconstructed from tree-ring records. Three statistically significant variations including the bi-decadal (~20yr), the tri-decadal (~30yr), and the multi-decadal (>50yr) variations are identified. The latter two variations exhibit 'phase-lock' features respectively with the bi-decadal variation: zero-crossings of the tri-decadal (multi-decadal) variation and the bi-decadal variation take place within significantly short duration. Above-mentioned characteristics imply that the two variations with longer timescale receive notable influence from the bi-decadal variation. These three variations together explain phase reversals identified using an instrumental 119-yr PDO index (1900-2018) including the period after 1997, where only the observed PDO index covers. Besides, these variations provide a viewpoint which integrates two contrary perspectives on the climatic regime shifts presented by previous studies. We further discuss possible linkages between these variations and the 18.6-yr lunar nodal cycle, as well as a phenomenon known as subharmonic resonances, which involves excitements of longer variations in nonlinear systems.