Why does the IOD-ENSO teleconnection disappear in some decades?

Abstract

Lag correlations between sea surface temperature anomalies (SSTA) in the southeastern tropical Indian Ocean (STIO) in fall and Niño 3.4 SSTA in the eastern equatorial Pacifi c in the following fall are subjected to decadal variation, with positive correlations during some decades and negative correlations during others. Negative correlations are smaller and of shorter duration than positive correlations. Variations in lag correlations suggest that the use of the Indian Ocean Dipole (IOD) as a predictor of the El Niño-Southern Oscillation (ENSO) at a lead time of one year is not effective during some decades. In this study, lag correlations between IOD and ENSO anomalies were analyzed to investigate why the IOD-ENSO teleconnection disappears during decades with negative correlations. Anomalies induced by the IOD in the equatorial Pacifi c Ocean during decades with negative correlations are still present, but at a greater depth than in decades with positive correlations, resulting in a lack of response to oceanic channel dynamics in the cold tongue SSTA. Lag correlations between oceanic anomalies in the west Pacifi c warm pool in fall and the equatorial Pacifi c cold tongue with a one-year time lag are signifi cantly positive during decades with negative correlations. These results suggest that oceanic channel dynamics are overwhelmed by oceanatmosphere coupling over the equatorial Pacifi c Ocean during decades with negative correlations. Therefore, the Indonesian throughfl ow is not effective as a link between IOD signals and the equatorial Pacifi c ENSO.

Assessment of the oceanic channel dynamics responsible for the IOD-ENSO precursory teleconnection in CMIP5 climate models

“…The IOD-ENSO precursory teleconnection, as represented by the running mean lag correlations between the STIO SSTA in fall and the Niño3.4 SSTA in the next fall, with a running window of 11, years, undergoes obvious decadal variability (Xu and Yuan, 2014). As shown in Figure 1A, the running mean lag correlations after the 1990s are positive, consistent with the analysis of Yuan et al (2013).…”

“…Thus, the teleconnection during the negative correlation periods is believed to be different from that during the positive correlation periods. The structure and possible dynamics of the teleconnection during the negative phases of the decadal variability have been analyzed in Xu and Yuan (2014). In this study, we only focus on the positive phases for two reasons.…”

“…In terms of the oceanic channel dynamic, it is identified to have positive and negative phases of decadal oscillations. The IOD-ENSO precursory teleconnection in SSTA during the negative phases are suppressed by decadal deepening of the thermocline in the eastern equatorial Pacific (Xu and Yuan, 2014).…”

Interbasin coupling between the tropical Indian and Pacific Ocean on interannual timescale: observation and CMIP5 reproduction

“…Ohba and Ueda (2009) demonstrated that the IOBM is associated with the atmospheric mean state via modulation of heat flux at the IO surface, whereas the IOD is caused by various dynamic and thermodynamic factors through wind modulation in the equatorial IO. Decadal changes in the IOBM and IOD also reveal distinct features and mechanisms (Ding et al 2010;Xu and Yuan 2015).…”

Decadal variability of the interannual climate predictability associated with the Indo-Pacific oceanic channel dynamics in CCSM4

“…The oceanic channel dynamics are evidenced by the propagation of sea level from the STIO to the western equatorial Pacific Ocean, giving rise to the significant lag correlations between the oceanic anomalies in STIO in fall and those in the Pacific equatorial vertical section and in the cold tongue at the one-year time lag (Yuan et al, 2013). Recent studies have also suggested that the IOD-ENSO teleconnection is subject to decadal and multi-decadal variations (Xu et al, 2013;Izumo et al, 2014;Xu and Yuan, 2015), the dynamics of which are not clear at present.…”