Impact of the GeoMIP G1 sunshade geoengineering experiment on the Atlantic meridional overturning circulation

• Published in: Environmental Research Letters
• Main Authors: Yu Hong, John C Moore, Svetlana Jevrejeva, Duoying Ji, Steven J Phipps, Andrew Lenton, Simone Tilmes, Shingo Watanabe, Liyun Zhao
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publishing 2017
• Subjects: ocean temperatures; circulation modelling; turbulent fluxes; Environmental technology. Sanitary engineering; TD1-1066; Environmental sciences; GE1-350; Science; Q; Physics; QC1-999; Arctic; Greenland; Ice; Ice Sheet; North Atlantic; permafrost; Sea ice
• Online Access: https://doi.org/10.1088/1748-9326/aa5fb8; https://doaj.org/article/3250a54d378146b4b0dd0c5d0187d541

We analyze the multi-earth system model responses of ocean temperatures and the Atlantic Meridional Overturning Circulation (AMOC) under an idealized solar radiation management scenario (G1) from the Geoengineering Model Intercomparison Project. All models simulate warming of the northern North Atlantic relative to no geoengineering, despite geoengineering substantially offsetting the increases in mean global ocean temperatures. Increases in the temperature of the North Atlantic Ocean at the surface (∼0.25 K) and at a depth of 500 m (∼0.10 K) are mainly due to a 10 Wm ^−2 reduction of total heat flux from ocean to atmosphere. Although the AMOC is slightly reduced under the solar dimming scenario, G1 , relative to piControl , it is about 37% stronger than under abrupt4 × CO _2 . The reduction of the AMOC under G1 is mainly a response to the heat flux change at the northern North Atlantic rather than to changes in the water flux and the wind stress. The AMOC transfers heat from tropics to high latitudes, helping to warm the high latitudes, and its strength is maintained under solar dimming rather than weakened by greenhouse gas forcing acting alone. Hence the relative reduction in high latitude ocean temperatures provided by solar radiation geoengineering, would tend to be counteracted by the correspondingly active AMOC circulation which furthermore transports warm surface waters towards the Greenland ice sheet, warming Arctic sea ice and permafrost.