Preprints
https://doi.org/10.5194/acp-2021-877
https://doi.org/10.5194/acp-2021-877

  12 Nov 2021

12 Nov 2021

Review status: this preprint is currently under review for the journal ACP.

Impacts of three types of solar geoengineering on the North Atlantic Meridional Overturning Circulation

Mengdie Xie1, John C. Moore1,2,3, Liyun Zhao1,4, Michael Wolovick1, and Helene Muri5 Mengdie Xie et al.
  • 1College of Global Change and Earth System Science, Beijing Normal University, Beijing, 100875, China
  • 2CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100101, China
  • 3Arctic Centre, University of Lapland, Rovaniemi, 96101, Finland
  • 4Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519082, China
  • 5The Industrial Ecology Programme, Norwegian University of Science and Technology, Trondheim, Postboks 8900, NO-7491, Norway

Abstract. Climate models simulate lower rates of North Atlantic heat transport under greenhouse gas climates than at present due to a reduction in the strength of the North Atlantic meridional overturning circulation (AMOC). Solar geoengineering whereby surface temperatures are cooled by reduction of incoming shortwave radiation may be expected to ameliorate this effect. We investigate this using six Earth System Models running scenarios from GeoMIP (Geoengineering model intercomparison project) in the cases of: i) reduction in the solar constant, mimicking dimming of the sun; ii) sulfate aerosol injection into the lower equatorial stratosphere; and iii) brightening of the ocean regions mimicking enhancing tropospheric cloud amounts. We find that despite across model differences, AMOC decreases are attributable to reduced air-ocean temperature differences, and reduced September Arctic sea ice extent, with no significant impact from changing surface winds or precipitation-evaporation. Reversing the surface freshening of the North Atlantic overturning regions caused by decreased summer sea ice sea helps to promote AMOC. Comparing the geoengineering types after normalizing them for the differences in top of atmosphere radiative forcing, we find that solar dimming is more effective than either marine cloud brightening or stratospheric aerosol injection.

Mengdie Xie et al.

Status: open (until 24 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Mengdie Xie et al.

Mengdie Xie et al.

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Short summary
We use 6 Earth System Models output data to estimate the AMOC changes and its drivers under 4 different solar geoengineering. Solar dimming seems relatively more effective than either marine cloud brightening or stratospheric aerosol injection at reversing greenhouse gas driven declines in AMOC. Geoengineering-induced AMOC amelioration is due to better maintenance of air-sea temperature differences and reduced loss of Arctic summer sea ice.
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