The Pacific and Atlantic play pivotal role in modulating global climate across interannual and decadal timescales. However, the interactions between these two tropical basins remain elusive. Utilizing a Linear Inverse Modeling (LIM) diagnostic approach, this study investigates the changes in Pacific-Atlantic coupling at interannual and decadal timescales before and after 1990. We conduct LIM experiments based on Ocean Reanalysis System 5 dataset at two distinct periods (pre-1990 and post-1990). The role of Pacific-Atlantic interaction in driving Pacific and Atlantic climate variability is investigated by removing the interactions from Pacific to Atlantic and from Atlantic to Pacific. On the interannual timescale, the Pacific dominated Atlantic variability prior to 1990, while the negative feedback from the Atlantic tended to damp Pacific variability. Conversely, post-1990, the influence from Atlantic emerged, but the Pacific also significantly impacts the Atlantic. This two-way feedback significantly amplified Pacific interannual variability. On the decadal timescale, an absolutely reversal of dominant basin in Pacific-Atlantic interaction occurred. The Pacific controlled the Atlantic before 1990 with the feedback form the Atlantic enhancing Pacific variability, whereas the Atlantic controlled the Pacific after 1990. Notably, the subsequent Pacific feedback post-1990 acted to weaken the Atlantic's influence on the Pacific. These findings highlight a critical transition from Pacific-dominated to Atlantic-dominated climate coupling around 1990, underscoring the necessity of accounting for inter-basin interactions to improve predictable skills for global climate.

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