Title: On the mechanisms of decadal variability of the North Pacific Gyre Oscillation over the 20th century

Journal: Journal of Geophysical Research: Oceans,120, 6114–6129

Authors: YI L.-D.-L.*, L. -P. Zhang, and L. -X. Wu

Abstract:The decadal variability of the North Pacific gyre oscillation (NPGO) over the 20th century isexamined from a long-term integration of the Simple Ocean Data Assimilation (SODA) reanalysis. The NPGOis reflected by the second dominant pattern of sea surface height (SSH) variability in SODA, with a northsouthdipole structure over the northeast Pacific. SSH anomalies in this region exhibit distinct decadal variabilitywith a significant spectrum peak at approximately 18 years. The upper-ocean heat budget revealsthat this dipole structure associated with the NPGO is predominantly due to the anomalous Ekman pumpingand Ekman advection induced by the surface wind. The NPGO mode in SODA reanalysis originates fromatmosphere stochastic noise (North Pacific Oscillation) which has a meridional dipole pattern but no preferredtime scale. The oceanic planetary wave, particularly the advective baroclinic mode, integration ofatmospheric stochastic noise leads to a spatial resonance with preferred decadal time scale. The limitationof current study is also discussed.