High‐Latitude Stratospheric Aerosol Injection to Preserve the Arctic. Issue 1 (19th January 2023)

• Record Type: Journal Article
• Authors: Lee, Walker Raymond; MacMartin, Douglas G.; Visioni, Daniele; Kravitz, Ben; Chen, Yating; Moore, John C.; Leguy, Gunter; Lawrence, David M.; Bailey, David A.
• Is Part Of: Earth's future. Volume 11:Issue 1(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-19
• Subjects: geoengineering -- stratospheric aerosol injection -- high‐latitude aerosol injection -- sea ice -- permafrost -- Greenland ice sheet; Environmental sciences -- Periodicals; Environmental sciences; Periodicals; 550
• DOI: 10.1029/2022EF003052
• Languages: English
• ISSNs: 2328-4277

Abstract

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 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 produces the most cooling near the pole, 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. For these reasons, it would be incorrect to consider Arctic‐focused SAI as "local" geoengineering, even when compared to a globally focused strategy. Plain Language Summary: The injection of reflective particles called sulfate aerosols into the atmosphere to reflect sunlight, commonly called "stratospheric aerosol injection" (SAI) or simply "geoengineering, " could be used alongside emission cuts and CO2 removal to cool the planet and reduce global warming. Concentrating this particle injection at high latitudes could be used to preserve the Arctic. We simulate such "Arctic‐focused" geoengineering and find that it does indeed preserve sea ice, permafrost, and the Greenland Ice Sheet. However, focusing on the Arctic also introduces complications: large quantities of carbon are stored by plants at mid‐to‐high latitudes, and cooling the Arctic may reduce their ability to take up carbon from the atmosphere. Additionally, cooling the Arctic more than the tropics could affect the way heat is transported around the planet, changing important precipitation patterns near the equator. Finally, most of the injected sulfur would come back down in the highly populated middle latitudes and the relatively pristine high latitudes, likely affecting ecosystems in both regions. For these reasons, we find that even though such an "Arctic‐focused" geoengineering would predominantly cool the Arctic, it would be incorrect to think of it as a "local" intervention, as it would affect the rest of the planet too. Key Points: Stratospheric aerosol injection at high latitudes could preferentially reduce the impacts of global warming in the Arctic Simulations of such injection increase sea ice and permafrost extents and preserve Greenland ice sheet mass High latitude injection preserves the Arctic more efficiently than tropical injection but also substantially affects tropical precipitation