Preprints
https://doi.org/10.5194/tc-2020-347
https://doi.org/10.5194/tc-2020-347

  04 Dec 2020

04 Dec 2020

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

Brief Communication: Reduction of the future Greenland ice sheet surface melt with the help of solar geoengineering

Xavier Fettweis1, Stefan Hofer1,2, Roland Séférian3, Charles Amory1,4, Alison Delhasse1, Sébastien Doutreloup1, Christoph Kittel1, Charlotte Lang1, Joris Van Bever1,5, Florent Veillon1, and Peter Irvine6 Xavier Fettweis et al.
  • 1SPHERES research units, Geography Department, University of Liège, Liège, Belgium
  • 2Department of Geosciences, University of Oslo, Oslo, Norway
  • 3CNRM, Université de Toulouse, Météo-France, CNRS, Toulouse, France
  • 4Univ. Grenoble Alpes, CNRS, Institut des Géosciences de l’Environnement, Grenoble, France
  • 5Earth System Science, Departement Geografie, Vrije Universiteit Brussel, Brussels, Belgium
  • 6Earth Sciences, University College London, London, UK

Abstract. The Greenland Ice Sheet (GrIS) will be losing mass at an accelerating pace throughout the 21st century, with a direct link between anthropogenic greenhouse gas emissions and the magnitude of Greenland mass loss. Currently, approximately 60 % of the mass loss contribution comes from surface melt and subsequent meltwater runoff, while 40 % are due to ice calving. Where most of the surface melt occurs (in the ablation zone), most of the energy for the surface melt is provided by absorbed shortwave fluxes, which could be reduced by solar geoengineering measures. However, so far very little is known about the potential impacts of an artificial reduction of the incoming solar radiation on the GrIS surface energy budget and the subsequent change in meltwater production. By forcing the regional climate model MAR with the latest CMIP6 future scenarios ssp245, ssp585 and associated G6solar experiment from the Earth System Model CNRM-ESM2-1, we evaluate the local changes due to the reduction of the solar constant on the projected GrIS surface mass balance (SMB) decrease. Overall, our results show that even in case of low mitigation greenhouse gas emissions scenario (ssp585), the Greenland surface mass loss can be brought in line with the medium mitigation emissions scenario (ssp245) by reducing the solar downward flux at the top of the atmosphere by ~40 W/m2 or ~1.5 % (using the G6solar experiment). In addition to reduce Global Warming in line with ssp245, G6solar also decreases the efficiency of surface meltwater production over the Greenland ice sheet by damping the well-known positive melt-albedo feedback which mitigates the projected Greenland ice sheet surface melt increase by 6 %. However, only more constraining geoengineering experiments than G6solar allows to maintain positive SMB till the end of this century without any reduction in our greenhouse gas emissions.

Xavier Fettweis et al.

 
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Xavier Fettweis et al.

Xavier Fettweis et al.

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Short summary
Without any reduction in our greenhouse gas emissions, the Greenland ice sheet surface mass loss can be brought in line with a medium mitigation emissions scenario by reducing the solar downward flux at the top of the atmosphere by 1.5 %. In addition to reduce Global Warming, these solar geoengineering measures also dampen by 6 % the well-known positive melt-albedo feedback over the ice sheet. However, only stronger reductions of solar radiation could maintain a stable ice sheet in 2100.