Decadal sea surface height modes in the low-latitude northwestern Pacific and their contribution to the North Equatorial Current transport variation

Three decadal sea surface height (SSH) modes in the low-latitude northwestern Pacific over 1958 − 2018 were revealed by empirical orthogonal function analysis of decadal SSH anomalies derived from the Ocean Reanalysis System 4 provided by the European Centre for Medium-Range Weather Forecasts. The two leading SSH modes present large and small cyclonic signals in the northwestern tropical Pacific and a localized domain of (120 − 150 °E, 6 − 14 °N), respectively. In contrast, the third SSH mode demonstrates positive basin-scale signals from 7 to 21 °N. All three SSH modes enhance the NEC transport, with the most considerable contribution from the third mode. The temporal evolutions of the first and third modes are more relevant to the decadal NEC transport variation before 1976, whereas the second and third modes become more important after then. Further investigations suggest that the first and second SSH modes correlate well with the time series of the two leading EOFs of the Tropical Pacific Decadal Variability, and the third SSH mode moderately correlates with the Pacific Decadal Oscillation. Using a linear reduced gravity model, the three SSH modes are reproduced with the wind forcing patterns regressed against the climate indices. This study is a new attempt and deepens our understanding of the decadal variability of the NEC by revealing the linkages between multiple SSH modes and Pacific climate indices.