Wind-Driven Circulation Feedbacks Offset Tropical Geoengineered Sea Salt Emissions

We employ simulations of enhanced, geoengineered sea salt aerosol (SSA) emissions in the tropics using a NOAA GFDL climate model to examine the circulation response. In the coupled simulations, increased tropical SSA emissions cool the deployment region and weaken the Equator–mid-latitude temperature gradient. This triggers circulation feedbacks, including weakened westerlies, which in turn suppress SSA emissions in both tropical and extratropical regions. These circulation-driven reductions offset 23% of the tropical geoengineered SSA increase. Emission changes are primarily controlled by wind speed and secondarily by temperature. In contrast, fixed-SST simulations yield rapid adjustments that increase SSA emissions overall—opposite in sign to the much larger emission changes in the coupled model. These findings show that aerosol injection strategies can modify both aerosol distribution and atmospheric circulation, potentially attenuating their intended climate effect.