Tropical Indian Ocean forcing on North American terrestrial and agricultural productivity decline under greenhouse warming

Tropical Indian Ocean warming has intensified under greenhouse forcing, yet its influence on North American terrestrial and agricultural productivity remains poorly understood. Here we show that summer tropical Indian Ocean warming is linked to widespread drying and reduced gross primary productivity across North America. Observations and model simulations reveal that tropical Indian Ocean-induced atmospheric heating excites stationary Rossby wave trains, which establish a high-pressure ridge over western North America and suppresses moisture transport into the continent. This leads to reduced precipitation and soil moisture, leading to 10-20% reductions in terrestrial productivity and crop yields. The relationship persists after excluding El Niño–Southern Oscillation years and is reproduced in multiple climate models, showing robust teleconnection processes. These results highlight a previously underappreciated pathway through which tropical Indian Ocean warming can weaken the North American land carbon sink under future climate change.