Fig. 4: Inter-model relationship between southward wind shift pattern and tropical Pacific recharge rate.

A Inter-model regression pattern of the skewness in net meridional heat transport along the integrated tropical Pacific boundary (see “Methods”) onto inter-model differences in the southward wind shift pattern. The integrated vertical profile of the meridional heat transport is a summation of that along both 10°S and 10°N; as such it represents the net meridional heat transport into (positive) or out of (negative) the tropical Pacific Ocean. B Relationship between the inter-model differences in the southward wind shift pattern and the skewness of recharge rate integrated over the domain of (160°E–100°W, upper 300 m) as indicated by the black box in (A). The correlation coefficient, slope and p value are indicated. C The inter-model relationship between the southward wind shift and skewness of thermocline gradient. The thermocline gradient is calculated as the west-minus-east using thermocline depth averaged over the western tropical Pacific Ocean (5°S–5°N, 160°E–120°W) and the eastern tropical Pacific Ocean (5°S–5°N, 120°W–80°W). D The inter-model relationship between the southward wind shift and ENSO nonlinearity (α; see “Methods”). Models with greater negative α simulate stronger nonlinear Bjerknes feedback with more distinctive Central Pacific and Eastern Pacific ENSO regimes (see “Methods”). The inter-model differences in the southward wind shift governs the inter-model spread in the discharge-recharge propensity of the tropical Pacific Ocean heat content through its modulation on thermocline tilt across the tropical Pacific Ocean; it also contributes to ENSO nonlinearity, highlighting its important role in the nonlinear ENSO air-sea feedback.