Preprints
https://doi.org/10.5194/tc-2021-318
https://doi.org/10.5194/tc-2021-318

  19 Oct 2021

19 Oct 2021

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

Insensitivity of mass loss of Icelandic Vatnajökull ice cap to solar geoengineering

Chao Yue1, Louise Steffensen Schmidt2, Liyun Zhao1,3, Michael Wolovick1,4, and John C. Moore1,5,6 Chao Yue et al.
  • 1College of Global Change and Earth System Science, Beijing Normal University, 100875 Beijing, China
  • 2Department of Geosciences, University of Oslo, 0316 Oslo, Norway
  • 3Southern Marine Science and Engineering Guangdong Laboratory, 519000 Zhuhai, China
  • 4Alfred Wegener Institute, 27570 Bremerhaven, Germany
  • 5CAS Center for Excellence in Tibetan Plateau Earth Sciences, 100101 Beijing, China
  • 6Arctic Centre, University of Lapland, 96101 Rovaniemi, Finland

Abstract. Geoengineering by stratospheric aerosol injection (SAI) may reduce the mass loss from Vatnajökull ice cap (VIC), Iceland, by slowing surface temperature rise, despite relative increases in ocean heat flux brought by the Atlantic Meridional Circulation (AMOC). Although surface mass balance (SMB) is affected by the local climate, the sea level contribution is also dependent on ice dynamics. We use the Parallel Ice Sheet Model (PISM) to estimate the VIC mass balance under the CMIP5 (Coupled Model Intercomparison Project Phase 5) RCP4.5, 8.5 and GeoMIP (Geoengineering Model Intercomparison Project) G4 SAI scenarios during the period 1982–2089. The G4 scenario is based on the RCP4.5, but with additional 5 Tg yr−1 of SO2 injection to the lower stratosphere. By 2089, G4 reduces VIC mass loss from 16 % lost under RCP4.5, to 12 %. Ice dynamics are important for ice cap loss rates, increasing mass loss for RCP4.5 and G4 by 1/4 to 1/3 compared with excluding ice dynamics, but making no difference to mass loss difference under the scenarios. We find that VIC dynamics are remarkably insensitive to climate forcing partly because of AMOC compensation to SMB and low rates of iceberg calving making ocean forcing close to negligible. But the exceptionally high geothermal heat flow under parts of the ice cap which produces correspondingly high basal melt rates means that surface forcing changes are relatively less important than for glaciers with lower geothermal heat flow.

Chao Yue et al.

Status: open (until 14 Dec 2021)

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Chao Yue et al.

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Short summary
We use the ice sheet model PISM to estimate Vatnajökull mass balance under solar geoengineering. We find that Stratospheric aerosol injection at the rate of 5 Tg yr−1 reduces ice cap mass loss by 4 percentage points relative to the RCP4.5 scenario. Dynamic mass loss is a significant component of mass balance, but insensitive to climate forcing.