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. However, due to the changes in ocean memory over the past few decades, its impact on monsoon predictions remains unclear. The persistence of sea surface temperature (SST) anomalies, as a key indicator of ocean memory, can regulate the local air-sea coupling processes affecting the Asian-Australian monsoon (A-AM), thereby significantly influencing climate predictions for Asia, Australia, and the entire Indo-Pacific region. Based on observational and numerical modeling evidence, the study finds that within the context of interdecadal variation in ocean memory, the seasonal persistence of Maritime Continent (MC) SST anomalies is more pronounced during the strong memory epoch (1982–1999), sustaining the anomalous western North Pacific anti-cyclone (WNPAC) through a stronger Matsuno-Gill response during the decaying phase of El Niño-Southern Oscillation (ENSO), thereby enhancing the overall strength of the A-AM system during the monsoon year. Additionally, the connection between ENSO and the A-AM is strengthened. By 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 early 21st-century decline in MC ocean memory reduced the prediction skills of the leading mode of the A-AM. Above all, this study emphasizes the significant impact of ocean memory on monsoon prediction skills, providing new insight into seeking more reliable sources of predictability for the A-AM.