*This item and others will be in the monthly “Solar Geoengineering Updates Substack” newsletter:* https://solargeoengineeringupdates.substack.com/ -----------------------------------------------------------------
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023JF007112 *Authors* John C. Moore, Ralf Greve, Chao Yue, Thomas Zwinger, Fabien Gillet-Chaulet, Liyun Zhao *First published: 27 November 2023* https://doi.org/10.1029/2023JF007112 *Abstract* Sea level rise (SLR) due to surface melt and to dynamic losses from the ice sheets—that is via accelerated flow of glaciers into the sea—is something that may be potentially mitigated by cooling the ice sheet and oceans via solar geoengineering. We use two ice dynamic models driven by changes in surface mass balance (SMB) from four climate models to estimate the SLR contribution from the Greenland ice sheet under the Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathway (RCP) 4.5, and 8.5, and Geoengineering Model Intercomparison Project G4 scenarios. The G4 scenario adds 5 Tg/yr sulfate aerosols to the equatorial lower stratosphere (equivalent of 1/4 the 1991 Mt Pinatubo SO2 eruption) to the IPCC RCP4.5 scenario, which itself approximates the greenhouse gas emission commitments agreed in Paris in 2015. Over the 2020–2090 period, mass loss under G4 is about 31%–38% that under RCP4.5, which is 36%–48% lower than under RCP8.5. Ice lost across the grounding line under both G4 and RCP4.5 is reduced in the future as the termini of many southeast Greenland outlets retreat onto bedrock above sea level. Glaciers with large low-lying catchments in the west, north, and northeast of Greenland (e.g., Jakobshavn, 79N, Zachariae Isstrøm, and Petermann glaciers) discharge more ice from the ice-sheet interior under RCP4.5 than under G4. Although calving losses vary much more than the SMB difference between ice dynamic models, both models point to significant ice discharge losses of between 15% and 42% across the scenarios. *Key Points* •Stratospheric aerosol injection at the rate of 5 Tg/yr (G4) lowers Greenland mass loss relative to RCP4.5 by 31%–38% by 2090 •Across four Earth System Model and two ice dynamic models (G4–RCP4.5) differences are 34%–40% in surface mass balance and 16%–34% in ice discharge •Dynamic mass loss by calving from glaciers is the largest uncertainty between ice dynamics models *Plain Language Summary* Sea level rise from Greenland over the next century may be around 10 cm by 2100. But the amount, and the long-term stability of the ice sheet depend on the degree of summer warming it experiences. Limiting greenhouse gas emissions to the levels pledged by states under the 2015 Paris agreement cuts ice sheet losses by 1/3–1/2 of the losses under the business-as usual-emissions scenario. If further cooling is induced by aerosols put into the stratosphere at a rate of about 1/4 of the 1991 eruption of Mt Pinatubo, then the ice sheet loss is reduced by about 30% compared with Paris emissions. This specific aerosol geoengineering scenario maintains both the deep and fast-flowing glaciers and the smaller mountain glaciers closer to present sizes than they would be under a greenhouse gas emission scenario similar to international pledges in the 2015 Paris agreement. Iceberg calving remains the most difficult to quantify aspect of Greenland ice loss. [image: Details are in the caption following the image] <https://agupubs.onlinelibrary.wiley.com/cms/asset/2673ce96-1331-4fe8-894a-2746d02c9775/jgrf21835-fig-0001-m.jpg> Figure 1:Eleven-year moving averaged anomalies of (a) surface mass balance and (b) surface Greenland air temperature, surface temperature, that drive the ice dynamics models. The anomalies are relative to 1979–1989 (for the historical run [hist] relative to 1960–1989). Labels “XXX-yyy” refer to the Earth System Models (ESMs) and scenarios, “Mean” denotes the four-ESM mean [image: Details are in the caption following the image] <https://agupubs.onlinelibrary.wiley.com/cms/asset/451fc7ee-d50b-4ce4-afde-eec80c1e0958/jgrf21835-fig-0005-m.jpg> Figure 5:Same as Figure 4 <https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023JF007112#jgrf21835-fig-0004> but for the Elmer/Ice simulations. [image: Details are in the caption following the image] <https://agupubs.onlinelibrary.wiley.com/cms/asset/cd7d2653-b134-402a-98cd-b3ba72d325c4/jgrf21835-fig-0006-m.jpg> Figure 6(a, c) G4–RCP4.5 change in volume flux *Q* (depth-integrated velocity on a positive/negative logarithmic scale), (b, d) G4–RCP4.5 change in ice sheet thickness *H* (square root scale) in 2090. Four-Earth System Model ensemble means from (a, b) SICOPOLIS and (c, d) Elmer/Ice. Outer (thick) black line: land margin, inner (thin) black line: ice margin in 2015, dashed black line: Jakobshavn drainage basin. Major marine-terminating glaciers: Nioghalvfjerdsfjorden Glacier (79N), Zachariae Isstrøm, Storstrømmen (SS), Kangerlugssuaq Glacier (K), Helheim Glacier (H), Jakobshavn Isbrae (J), Upernavik Isstrøm, Steenstrup Glacier (S), and Petermann Glacier (P). *Source: AGU* -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/CAHJsh9_X%3DNvZK_J9AqpOjZv3K07NK15UdXbPFsPoHPq8pEwH1A%40mail.gmail.com.
