资源环境科技发展态势分析平台

Sea surface temperature (SST) in the midlatitude south Indian Ocean (MSIO) exhibits prominent multidecadal fluctuations that have profound climate impacts for regions around the Indian Ocean. Observational analysis suggests that these multidecadal fluctuations can be explained by remote forcing from South Atlantic multidecadal variability. A suite of Atlantic Pacemaker experiments performs well in reproducing the observed MSIO SST multidecadal variation and its association with the South Atlantic. This transbasin covariability can be described by an atmospheric bridge mechanism, in which South Atlantic multidecadal variability-related SST warming weakens regional meridional circulation over the South Atlantic, suppressing convection over tropical Africa. The reduced diabatic heating then drives a cold atmospheric Kelvin wave that penetrates into the tropical Indian Ocean, leading to an anomalous cyclonic circulation there that weakens the westerlies over the MSIO and subsequently triggers the warming of MSIO. This initial warming is further amplified by local SST-water vapor positive feedback over the MSIO.