University of Melbourne researchers published the findings late on Tuesday in a peer-reviewed paper that also found rising temperatures could create persistent El Niño-like conditions in the region.
Cutting emissions sooner could limit the extent of the changes, they said, but some nations would need to adapt to warmer conditions.
The study comes weeks before ocean-related climate threats are expected to become a key issue at the United Nations' COP31 talks in Antalya, Turkey, following calls for action from Pacific leaders at pre-COP31 in Fiji.
The research, published in the Communications Earth and Environment journal, analysed global climate simulations and used a CSIRO computer modelling system to project changes for 1000 years after emissions ceased.
The modelling showed ending emissions did not immediately reverse the effects of climate change in the tropical Pacific Ocean, University of Melbourne researcher and lead author Aditya Sengupta said, and the impact could continue for centuries.
"The atmosphere and the ocean surface can adjust relatively quickly, while the deep ocean absorbs and releases heat over hundreds or even thousands of years," he said.
"This gives the ocean a long memory of previous greenhouse gas emissions."
The modelling found global warming could cause a lasting shift towards El Niño-like conditions in the Pacific Ocean.
El Niño events are associated with hotter and drier conditions in Australia and an increased risk of drought and bushfires.
The findings did not mean the Pacific would be locked in a permanent El Niño event, researchers said, but would mean a long-term change to the ocean's temperature patterns.
The results underlined the importance of cutting greenhouse gas emissions to curtail global warming, University of Melbourne associate professor and co-author Andrew King said - and to move swiftly.
"We found clear benefits from reducing emissions quickly," he said.
"Reaching net zero earlier limits the changes occurring within the ocean and reduces the risk of leaving future generations with a substantially altered tropical Pacific."
The COP31 event, which begins on November 9, has listed 10 priorities for climate discussions, including ocean observation and greater resilience for coastal and marine ecosystems.
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