In the past decade, the scientific community has recognized the interaction between the tropical basins of the Pacific, Atlantic, and Indian Oceans—known as Tropical Basin Interactions (TBI)—as a key element for understanding climate variability on interannual to decadal timescales. Pioneering studies by the TROPA group, which leads this project, have made a crucial contribution to this new paradigm. These studies showed that, contrary to the previously dominant view that considered Pacific El Niño–Southern Oscillation (ENSO) as the only source of influence and predictability in the tropical region, Atlantic Niño variability in summer could trigger an ENSO event the following winter. This influence becomes evident in the decades after the 1970s, suggesting a non-stationary nature for TBIs.

Subsequent studies proposed that sea surface temperatures (SSTs) in the Indian or Tropical North Atlantic basins could also influence ENSO development.

Despite the growing number of studies aimed at improving the understanding of TBIs, many key questions remain open. Among them, the causes of interannual TBI modulations on timescales of one to several decades are still under debate. Some studies suggest that changes in patterns associated with TBI modes could be important for linking the basins. Others propose that decadal SST variability patterns, such as the Atlantic Multidecadal Variability (AMV) or changes in Pacific SST climatology, may play a crucial role in modulating interannual TBIs. Finally, the role of the deep ocean remains unexplored.

The DISTROPIA project investigates the causes of interannual TBI modulation from two complementary perspectives. On one hand, it focuses on variability on decadal timescales and explores its impacts on key elements of the coupled ocean-atmosphere system, including TBIs. On the other hand, it examines interannual TBIs by analyzing the mechanisms that produce their changes from one decade to another.

Moreover, the impacts of TBIs are still not fully understood, and their potential use for improving climate predictions remains underexploited. Recent studies suggest that ENSO dynamic forecasts could be enhanced using information on the state of the Atlantic and Indian basins. However, the impacts of TBIs on interannual climate variability in the European region or in West Africa remain uncertain. The DISTROPIA project will deepen our understanding of these impacts and assess the relevance of TBIs for the skill of operational dynamic predictions of ENSO and the West African Monsoon.

The project relies on the analysis of sensitivity experiments, long historical and control simulations, dynamic forecasts, and the use of a new generation of observational products developed by the project team. DISTROPIA also adopts a novel energetic perspective and applies complex network analysis methodologies, enabling a broader understanding of TBIs. In summary, the project represents a major step forward in understanding the processes involved in TBIs, their impacts, and their decadal modulations