The Impact of Different Stratospheric Aerosol Injection Strategies on the Antarctic Region

Stratospheric aerosol injection (SAI) is a proposed geoengineering strategy to aid the effort to minimize the negative effects of climate change and global warming. Research shows that altering the amount, latitude, and time of year of the sulfate aerosol injection will alter patterns of surface temperature and precipitation changes, among other climate signatures. However, there exists minimal research evaluating the various SAI approaches and their impact on Antarctica. Here, we examine ten such SAI strategies that vary the latitude(s) and season of the injection with the injections beginning in 2035. These simulations are compared to a historical period (1985-2015) and a future emission scenario (SSP2-4.5) to evaluate their impact on Antarctica surface temperature and precipitation as well as the surrounding shelf ocean temperature and salinity. Each strategy uniquely alters atmospheric circulation around the continent expressed through changes in the Southern Annular Mode. Specifically, injections in the northern hemisphere typically lead to a more positive SAM index compared to the historical or SSP2-4.5 simulations. A positive SAM drives an upwelling of off-shelf subsurface warm water (Circumpolar Deep Water) onto the continental shelf. This can lead to increase melt rates for ice shelves around Eastern Antarctica compared to the historical or SSP2-4.5 simulations. Comparatively, injecting in the southern hemisphere decreases the SAM index and shelf water temperatures in this region. In addition to altering local wind stress, the various SAI strategies impact the shelf ocean freshwater budget through changes in precipitation, sea ice, and fluxes from the continent. Freshening of shelf waters can work to decrease the cross-shelf heat transport below the surface by strengthening the Antarctic Slope Front, effectively cooling the shelf waters; or freshening can initiate a "freshwater cap" which prevents upwards vertical heat transport, effectively warming the shelf waters. These freshwater processes play an important role in dictating the amount of warming or cooling on the Antarctic shelf due to the various SAI strategies, particularly in the Antarctic Peninsula and Amundsen Sea regions.