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Human-driven global warming may be disrupting the long-standing climate connection between the tropical Indian and Pacific oceans, making the recent changes unusually different from natural variations, a new study suggests.
Researchers at the Woods Hole Oceanographic Institution (WHOI) combined climate model simulations with evidence from corals, tree rings and stalagmites to reconstruct ocean climate patterns dating back to the early 1600s.
The study, published in Nature Communications, found that the Indian and Pacific oceans remained closely linked for most of the past 400 years. But major volcanic eruptions temporarily weakened that relationship between 1810 and 1850.
Climate simulations covering the past 1,000 years supported the finding, showing that the extent of disruption depended on the size of eruptions and prevailing climate conditions.
The researchers said the modern weakening of the ocean connection is different and appears far more unusual.
Since the 1980s, the Indian Ocean has increasingly behaved differently from what would normally be expected based on Pacific conditions, a shift scientists have associated with global warming.
“Global warming and human emissions are now overwhelming the Pacific’s natural influence on the Indian Ocean,” said Caroline Ummenhofer, a senior scientist at WHOI and co-author of the study.
Lead author Shawn Wang, a former WHOI researcher now at the University of Colorado Boulder, said combining modern observations with paleoclimate records and models provides stronger evidence that the recent changes are exceptional.
The findings could have implications for climate forecasting. The interaction between the Indian and Pacific oceans helps shape tropical rainfall, temperatures and atmospheric circulation. If that relationship changes, forecasts based on historical climate patterns could become less reliable.