Summary
The study examines how stratospheric aerosol geoengineering (SAG) affects sea surface temperatures (SSTs) in the Angolan Upwelling System. Under climate warming (RCP8.5), SSTs rise by ~1.65 °C due to stronger stratification, reduced vertical mixing, increased shortwave radiation, and a strengthened Angolan current. SAG reverses this trend, cooling SSTs by ~0.35 °C through enhanced vertical mixing and reduced solar radiation. Remote wind‑driven coastal trapped waves also influence SST changes under both warming and geoengineering scenarios.
Abstract
Stratospheric Aerosol Geoengineering (SAG), which involves injecting sulfur dioxide into the stratosphere, has been suggested as a potential method of limiting the impacts of global warming. This study examines the impact of SAG on Sea Surface Temperature (SST) in the Angolan Upwelling System (AUS), and the physical processes driving SST changes, using simulations from the Geoengineering Large Ensemble Project performed under the Representative Concentration Pathway 8.5 (RCP8.5). Results reveal that in the AUS region, under global warming, the SST increases significantly (compared to current climate), throughout the seasonal cycle with an average of around 1.65°C. This SST increase is mainly explained by the weakening of vertical mixing caused by a strong stratification at the base of the mixed-layer, particularly from April to October, and the increase in solar shortwave radiation during November/December. This SST increase is reinforced in September-October by changes in meridional advection, due to the intensification of the Angolan current, which is largely modulated by the coastal trapped waves. However, under SAG, the SST decreases throughout the year (relative to the current climate), by around −0.35°C on average. This SST cooling is mainly due to an increase in vertical mixing, particularly from October to March, driven by an increase in vertical temperature gradient at the base of the mixed-layer, and also to a decrease in solar shortwave radiation associated with SAG application. Finally, the findings also indicate that remote wind forcing (non-local processes) in the western equatorial Atlantic which generates coastal trapped waves, contribute to SST changes under both climate change and SAG.
