Mapping the delayed “conversation” between the world’s oceans

Climate signals move between ocean basins on timescales ranging from months to years.

The world’s oceans are having a conversation, and like good conversationalists they take turns to speak.

A new study published April 2 in Ocean-Land-Atmosphere Research finds that climate signals can take months or even years to travel between the Pacific, Atlantic and Indian oceans, with the dominant source of the signals shifting over time.

Covering more than 70% of the planet’s surface, the global ocean is divided into five named oceans. Whilst coastlines, straits and other geographical features may mark their boundaries, there are no walls separating them. And what flows between them is much more than just water: heat, energy, nutrients and more are also on the move, shaping Earth’s climate, chemistry and life.

“The global climate system is strongly influenced by interactions among the Pacific, Atlantic and Indian oceans,” said Shuheng Lin, professor at Fujian Normal University in China and corresponding author of this study.

Scientists have long sought to understand how climate signals, meaning measurable changes in climate variables such as sea surface temperature, move between ocean basins. But previous studies have often focused on individual oceans or specific climate patterns, missing the complex pathways that connect the global ocean system.

“We aimed to better understand the timing, direction and evolution of interactions among the three major ocean basins by developing a data-driven framework to identify delayed connections in sea surface temperature variability,” said Fenying Cai, first author and researcher at the Potsdam Institute for Climate Impact Research in Germany.

The team constructed time-lagged networks of observed sea surface temperatures. Unlike approaches based on predefined climate indices, complex network analysis can identify connections directly from the data. This method can reveal which regions tend to lead or lag at particular times, quantify delays between them, and map pathways linking distant parts of the climate system.

The results reveal a dynamic sequence of interactions.

On short timescales of up to six months, the Pacific has a strong influence on the Indian Ocean. After roughly one year, the Atlantic becomes an important driver of Pacific variability. On longer timescales of 20 months or more, signals from both the Indian and Pacific oceans are linked to subsequent changes in the Atlantic.

“The key message is that the three ocean basins are connected through a dynamic ‘relay system,’” Lin said. “The dominant source of climate signals shifts over time, revealing that global ocean interactions are more sequential and complex than previously recognized.”

The study also examined whether current climate models can reproduce these observed relationships. Models participating in a collaborative framework called CMIP6 (short for Coupled Model Intercomparison Project Phase 6), designed to improve knowledge of climate change, generally capture the short-term influence of the Pacific on the Indian Ocean. However, only a limited number reproduce the medium- and long-term connections involving the Atlantic.

All the models consistently project stronger cross-basin connections under future global warming. Such changes could affect the predictability of climate variability.

The findings offer a new way to view the global ocean, not as separate systems but as an interconnected network in which climate signals are passed from one basin to another, with the lead player changing as the years unfold.

The team’s next step is to investigate the mechanisms behind the delayed connections by combining complex network analysis with coupled ocean–atmosphere modeling experiments.

“Ultimately, our goal is to develop a more comprehensive understanding of global climate connectivity and improve predictions of climate variability, including phenomena such as El Niño and other climate extremes that affect societies worldwide,” Cai said.

Funding 

• Guangdong Major Project of Basic and Applied Basic Research (grant 2020B0301030004),
• National Natural Science Foundation of China (grants 42505021 and 42088101),
• Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (SML2023SP209),
• Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies (2023B1212060019),
• Postdoctoral Fellowship Program of China Postdoctoral Science Foundation (GZC20250218).