Wind‐Driven Circulation Feedbacks Offset Tropical Geoengineered Sea Salt Emissions

Abstract

Abstract Using a NOAA Geophysical Fluid Dynamics Laboratory coupled atmosphere–ocean (CM4) comprehensive model, we employ simulations of enhanced, geoengineered sea salt aerosol (SSA) emissions in the tropics to examine the circulation response to idealized marine cloud brightening. Increased tropical SSA emissions cool the deployment region and weaken the Equator‐to‐midlatitude temperature gradient, triggering circulation feedbacks that include weaker Southern Ocean westerlies. These circulation feedbacks suppress natural SSA emissions in both tropical and extratropical regions, offsetting about 23% of the imposed geoengineered SSA mass flux. In the offline sensitivity calculations, circulation feedbacks exert a weaker influence on aerosol number than on emitted mass (1% vs. 10%). Furthermore, wind speed is the primary driver of circulation‐induced changes in SSA mass emissions, with sea surface temperature (SST) playing a secondary role. For number flux, SST has a larger influence in some regions due to the predominance of smaller particles. These findings demonstrate that aerosol injections can alter both circulation and aerosol distribution, potentially attenuating their intended climate effect.