Interdecadal variability in ocean memory of the maritime continent and its effect on Asian–Australian monsoon prediction

Ocean memory is crucial for improving climate models and enhancing the accuracy of climate predictions. Despite its importance, the evolving influence of ocean memory over recent decades on monsoon predictions remains ambiguous. The persistence of sea surface temperature (SST) anomalies, a critical indicator of ocean memory, governs local air-sea coupling processes affecting the Asian-Australian monsoon (A-AM), thereby significantly shaping climate predictions for Asia, Australia, and the broader Indo-Pacific region. Drawing on observational and numerical modeling evidence, the study elucidates that within the context of interdecadal variation in ocean memory, the seasonal persistence of Maritime Continent (MC) SST anomalies was more pronounced during the epoch of robust ocean memory (1982-1999). This persistence sustained the anomalous western North Pacific anticyclone (WNPAC) through an intensified Matsuno-Gill response in the decaying phase of El Niño-Southern Oscillation (ENSO), thereby enhancing its linkage with the A-AM system throughout the monsoon year, contributing to improved prediction skills of the A-AM. In contrast, these air-sea coupling processes have weakened during the weak memory epoch (2000-2017), making it more difficult to capture the characteristics of the A-AM. The decline in MC ocean memory at the onset of the twenty-first century has undermined the prediction skills of the leading modes of the A-AM. Overall, this study underscores the profound influence of ocean memory on monsoon prediction skills while highlighting the significant challenges in addressing A-AM variability and predictability against the backdrop of global warming.