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

Abstract

The lag correlations between the observed sea surface temperature anomalies (SSTA) in the southeastern tropical Indian Ocean in fall and those in the Pacific cold tongue at the one-year time lag are calculated in running windows of 7–11 years and are shown to have decadal variability. Similar decadal variability has also been identified in the historical simulations of the Community Climate System Model version 4 (CCSM4) that participates in the Coupled Model Intercomparison Project phase-5 (CMIP5). During the positive phases of the decadal variability, the significant lag correlations are diagnosed to be dominated by the oceanic channel dynamics, i.e., upwelling Kelvin waves associated with the Indian Ocean Dipole (IOD) force enhanced Indonesian Throughflow transport anomalies and western Pacific thermocline anomalies to propagate eastward, resulting in SSTA in the central-eastern equatorial Pacific Ocean. During the negative phases of the decadal variability, the subsurface lag correlations suggest that the western Pacific Ocean are still dominated by the oceanic channel dynamics, but do not correlate well with the SSTA in the cold tongue due to a deeper thermocline in the eastern equatorial Pacific. The IOD-ENSO teleconnection is not affected significantly by the anthropogenic forcing during either the positive or the negative decadal phases. The CCSM4 model is found to underestimate Indonesian Throughflow transport variability but overestimate the westerly wind anomalies in the western-central equatorial Pacific, which forces unrealistic anomalies in the equatorial Pacific Ocean associated with the IOD.

Sea level anomalies in the southeastern tropical Indian Ocean as a potential predictor of La Niña beyond one-year lead

“…Moreover, the auto-correlation at one year lag is not statistical significant in any decade after 1970 (figure not shown). In contrast, the IOD-ENSO lag correlation is strong during the 1990s (Yuan et al, 2022). Clearly, the ENSO autocorrelation is not the major cause of the IOD-ENSO lead-lag relationship.…”

“…Existing studies have focused on atmospheric teleconnection via the Walker circulation (Kug and Kang, 2006;Izumo et al, 2010;Ha et al, 2017). Other studies suggest that the "oceanic channel" of the Indonesian Throughflow (ITF) may provide an important connection between the Indian and Pacific Ocean climate variabilities (Yuan et al, 2011;Yuan et al, 2013;Mayer et al, 2018;Yuan et al, 2018;Wang et al, 2022;Xu et al, 2022;Yuan et al, 2022). The cold tongue SSTA were found to correlate significantly with sea level anomalies (SLA) in the southeastern tropical Indian Ocean (SETIO), the eastern pole of the IOD, one year before.…”