Decadal to Multi-Decadal Circulation Variability in the Western Tropical Pacific Ocean
Event: 2022 Ocean Surface Topography Science Team Meeting
Session: Science II: Large Scale Ocean Circulation Variability and Change
Presentation type: Type Oral
Available satellite altimeter sea surface height (SSH) data from the past 28 years are used to investigate the decadal-to-multi-decadal ocean changes in the Western Tropical Pacific Ocean (WTPO). As represented by the North Equatorial Current (NEC) bifurcation off the Philippine coast, the low-frequency WTPO circulation variability is well captured by the altimeter-derived SSH data and which, in turn, can be quantified favorably by the wind-forced linear vorticity dynamics. Using the long-term ERA5 reanalysis wind stress data, we extend the wind-forced SSH record back to the 1950s. Over the past seven decades, the SSH-inferred circulation variability in the WTPO has lengthened from biennial in the 1970s, to interannual in the 1980s-1990s, to decadal in the recent two decades. Much of this period lengthening in the WTPO variability is caused by similar lengthening in the wind forcing field as a result of multi-decadal transitions from dominance by the Eastern Pacific-type of ENSO variability to that by the Central Pacific-type of ENSO variability.