Figure 3.

Seasonal SST anomalies (a) and δ¹⁸O_sw anomalies (b) during neutral years (blue line) and IOD years or post-IOD years (red line) before the regime shift. Dotted line: t-test results (neutral years vs. IOD years and neutral years vs. the post-IOD years, respectively). During boreal summer of positive and post IOD years, SST anomalies and δ¹⁸O_sw anomalies are higher than in neutral years. Seasonal SST anomalies (c) and δ¹⁸O_sw anomalies (d) during neutral years (blue line) and IOD years or post-IOD years (red line) after the regime shift. Dotted line: t-test results (neutral years vs. IOD years and neutral years vs. the post-IOD years, respectively). SST anomalies and δ¹⁸O_sw anomalies during neutral, positive-IOD and post IOD years are not significantly different.