Abstract
Stratospheric aerosol injection (SAI) has been shown in climate models
to reduce some impacts of global warming in the Arctic, including the
loss of sea ice, permafrost thaw, and reduction of Greenland Ice Sheet
(GrIS) mass; SAI at high latitudes could preferentially target these
impacts. In this study, we use the Community Earth System Model to
simulate two Arctic-focused SAI strategies, which inject at 60°N
latitude each spring with injection rates adjusted to either maintain
September Arctic sea ice at 2030 levels (“Arctic Low”) or restore it
to 2010 levels (“Arctic High”). Both simulations maintain or restore
September Arctic sea ice to within 10% of their respective targets,
reduce permafrost thaw, and increase GrIS surface mass balance by
reducing runoff. Arctic High reduces these impacts more effectively than
a globally-focused SAI strategy that injects similar quantities of
SO2 at lower latitudes. However, Arctic-focused SAI is
not merely a “reset button” for the Arctic climate, but brings about a
novel climate state, including changes to the seasonal cycles of
Northern Hemisphere temperature and sea ice and less high-latitude
carbon uptake relative to SSP2-4.5. Additionally, while Arctic-focused
SAI predominantly cools the Arctic, its effects are not confined to the
Arctic, including detectable cooling throughout most of the northern
hemisphere for both simulations, increased mid-latitude sulfur
deposition, and a southward shift of the location of the Intertropical
Convergence Zone (ITCZ).