March 11th, 2026

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Key Findings

• Changes in the Atlantic Ocean’s large-scale circulation influence tropical rainfall patterns.
• A weakening Atlantic Meridional Overturning Circulation (AMOC) reduces northward ocean heat transport, cooling the North Atlantic and relatively warming the tropical South Atlantic.
• These temperature differences shift trade winds and move the Atlantic Intertropical Convergence Zone (ITCZ) southward.
• Ocean circulation processes—particularly the North Atlantic subtropical gyre and western boundary current—play the dominant role in transmitting extratropical signals to the tropics.
• Results help explain why coupled models often underestimate tropical responses to AMOC variability and provide guidance for improving prediction of teleconnected impacts

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Rajat Joshi and Rong Zhang. npj Climate and Atmospheric Science DOI: 10.1038/s41612-025-01253-z

Changes in tropical rainfall can strongly affect water resources, agriculture, and communities across regions influenced by the Atlantic Ocean circulation. In this study, the authors used a high-resolution coupled atmosphere-ocean model and targeted freshwater-forcing experiments to understand how changes in Atlantic Ocean circulation influence tropical rainfall.

The simulations show that when the AMOC weakens, less heat is transported northward by the ocean. This produces cooler conditions in the North Atlantic and relatively warmer waters in the tropical South Atlantic. The resulting temperature contrast alters trade winds and shifts the band of strongest tropical rainfall southward during boreal summer, providing a physical explanation between Atlantic temperature patterns and rainfall changes.

The study further demonstrates that ocean circulation—rather than the feedback among surface wind, evaporation, and sea surface temperature proposed in previous studies without ocean dynamics—plays the leading role in carrying extratropical signals into the tropics along a horseshoe pathway. The North Atlantic subtropical gyre and western boundary current are especially important in shaping tropical responses.

By clarifying how large-scale ocean circulation affects tropical rainfall, this research strengthens the scientific basis for predicting regional oceanic and atmospheric changes and improving coupled model performance. These advances support NOAA’s mission to enhance rainfall prediction and help communities better prepare for ocean circulation-related risks.

Atlantic Extratropical–Tropical Teleconnection Response to Freshwater ForcingSchematic of the Atlantic extratropical-tropical teleconnection during boreal summer in response to prescribed freshwater forcing. NA: North Atlantic. SA: South Atlantic. SST: sea surface temperature. SAT: surface air temperature. ITCZ: Intertropical Convergence Zone.