Volcanic eruptions and warming climate disrupt long-standing link between Indian and Pacific oceans

A new study reveals that large volcanic eruptions and human-induced climate change are disrupting the connection between the tropical Indian and Pacific oceans. Researchers from Woods Hole Oceanographic Institution (WHOI) used paleoclimate data and climate models to show that volcanic activity can weaken links between ocean basins, while recent greenhouse gas emissions have caused an unprecedented shift in the relationship.

Scientists have observed a breakdown in the typical Indian Ocean response to Pacific Ocean behavior since the 1980s, but the study extends this record back to the early 1600s using tropical paleoclimate archives. Consistent with modern observations, the paleo-records indicate that the two ocean basins were largely coupled for most of the past 400 years.

However, the early 19th century (1810-1850) showed a notably different Indian-Pacific relationship, which the researchers attribute to a series of large tropical volcanic eruptions. These eruptions temporarily weakened Pacific influences on the Indian Ocean climate, with the extent of this weakening depending on the eruption strength and climate conditions.

Lead author Shawn Wang, now a postdoctoral researcher at the University of Colorado Boulder, emphasizes that the modern data is limited and that climate models and paleo-records help frame how exceptional the recent breakdown is. Understanding these changes is crucial, as connections between ocean basins help predict future climate patterns, including rainfall.