Sea Ice Targeted Geoengineering Can Delay Arctic Sea Ice Decline but not Global Warming - Zampieri - - Earth's Future - Wiley Online Library

[Andrew Lockley]

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019EF001230

Sea Ice Targeted Geoengineering Can Delay Arctic Sea Ice Decline but not Global Warming

Lorenzo Zampieri Helge F. Goessling

First published: 05 December 2019

https://doi.org/10.1029/2019EF001230

Lorenzo Zampieri and Helge F. Goessling contributed equally to this work.

Abstract

To counteract global warming, a geoengineering approach that aims at intervening in the Arctic ice‐albedo feedback has been proposed. A large number of wind‐driven pumps shall spread seawater on the surface in winter to enhance ice growth, allowing more ice to survive the summer melt. We test this idea with a coupled climate model by modifying the surface exchange processes such that the physical effect of the pumps is simulated. Based on experiments with RCP 8.5 scenario forcing, we find that it is possible to keep the late‐summer sea ice cover at the current extent for the next ∼60 years. The increased ice extent is accompanied by significant Arctic late‐summer cooling by ∼1.3 K on average north of the polar circle (2021–2060). However, this cooling is not conveyed to lower latitudes. Moreover, the Arctic experiences substantial winter warming in regions with active pumps. The global annual‐mean near‐surface air temperature is reduced by only 0.02 K (2021–2060). Our results cast doubt on the potential of sea ice targeted geoengineering to mitigate climate change.

[Sev Clarke]

This paper is targeted principally at the Ice Thickening concept proposed by the ASU Professors Steven Desch and Hilairy Hartnett et al. Whilst the Zampieri and Goessling modelling study is a useful contribution, its conclusions relate only to one method of ice thickening and should not be generalised beyond this. It takes little or no cognisance of other ice thickening methods that are designed to provide more substantial results. One such that is described at https://www.climate-restoration-foundation.com/winwick-business-solutions under the Ice Shields heading, and more recently in the attachment, has proposed effects that are not reflected in the model. Some of these include: a build-up of thickened ice that survives the summer melt and increases the thickness in later years; the pillared grounding of ice shield arrays in waters shallower than several hundred metres; the extension of ice thickened areas to the Antarctic and some sub-polar seas that still form sea ice in winter; the deep ocean cooling, CO2 sequestration and its partial conversion to bicarbonate by reaction with seabed carbonates as a result of the sinking of dense, chilled and gasified brine residual to brackish ice formation; the absorption by the thinly-flowing seawater on the surface of the forming ice shields of atmospheric CO2 and oxygen; the increased cold-season long wave radiation off-planet from the 'warmed' and relatively water vapour-rich thermal above each ice shield; the barrier effect of deep or grounded ice shield arrays in repelling the intrusion of warm surface currents into polar regions; the effect of ice bridges and barriers in retarding glaciers and the transport of sea ice away from the polar regions; and the contribution the chilled brine and ice shields could make to limiting the ebullition of seabed methane into the atmosphere and to the beneficial strengthening of the Great Ocean Conveyor Belt circulation. Whilst simplifying assumptions and approximations are common in modelling studies, it is thought that, understandably, the Z&G study does not reflect the critical nature of "ice formation at the surface instead of the bottom" when the Desch approach is replaced by that of the Ice Shield approach (including the likelihood that melt ponds would virtually be eliminated because of the conical form of each ice shield and the presence of intervening polynyas in the ice shield arrays that drain any surface meltwater). The colder that we can make the polar regions by such means in the warm season, the easier it would become to thicken ice and stabilise glacial melt and reduce breakup over a greater area and for a longer duration. Any modest increase in polar surface and atmospheric temperatures during the freezing season (say from an average of -40C to -30C) would likely to be well worth the cost.