Arctic Sea Ice Response to Flooding of the Snow Layer in Future Warming Scenarios. Issue 10 (11th October 2021)

• Record Type: Journal Article
• Authors: Pauling, Andrew G.; Bitz, Cecilia M.
• Is Part Of: Earth's future. Volume 9:Issue 10(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-10-11
• Subjects: sea ice -- geoengineering -- flooding -- future scenarios -- climate modeling; Environmental sciences -- Periodicals; Environmental sciences; Periodicals; 550
• DOI: 10.1029/2021EF002136
• Languages: English
• ISSNs: 2328-4277

Abstract

Abstract: The projected decline in Arctic sea ice extent as the Earth warms in response to increased greenhouse gas concentrations will occur in conjunction with increased precipitation in the Arctic, and more of that precipitation is projected to fall as rain, especially in autumn and early winter. A recently proposed method of offsetting the decline in Arctic sea ice extent would pump seawater on the sea ice surface. Either way, we envision the liquid water first infiltrating the overlying snow layer creating slush. Winter conditions would then freeze the slush to directly thicken the ice. The net reduction in insulation would increase basal growth, adding an indirect thickening effect. Simulating the response to augmented snow layer flooding gives insights that are relevant in the future Arctic with or without the implementation of geoengineering. We use a hierarchy of models to show that flooding snow on sea ice is most effective at thickening Arctic sea ice when flooding begins early in the sea ice growth season. For the geoengineering scheme to be most effective, the pumps must be deployed almost immediately, while there is still a sufficient area of sea ice over which to flood, and must continue for decades. Sea ice loss would be best mitigated if flooding is combined with reducing greenhouse gas emissions. Furthermore, the increase in rainfall over the Arctic in the 21st century is unlikely to offset a substantial portion of the loss due to warming. Plain Language Summary: As the Earth warms, the amount of sea ice in the Arctic will decline, more precipitation will fall over the Arctic, and a larger fraction of that precipitation will fall as rain. This rain can flood the snow layer on top of the sea ice, where it freezes in winter due to the cold atmosphere above, thickening the ice. This process is also relevant for a recently proposed method of "saving" the Arctic sea ice, by installing wind‐powered pumps in the Arctic Ocean which pump water onto the sea ice surface. Here, we investigate the consequences of flooding the overlying snow layer with liquid water. We use a range of simulations of sea ice, either alone or as part of the global climate system, to show that flooding the snow in winter freezes it more solid, directly increasing sea ice thickness. In addition, reducing the snow depth lowers insulation, driving an indirect thickening process. Flooding the snow alone cannot reverse the decline in Arctic sea ice, but may delay it, especially if combined with reducing greenhouse gas emissions. In any case, flooding the snow is a necessary first step before water can reach the ice and freeze on it. Key Points: Flooding the sea ice surface with seawater or rain may reduce sea ice loss in future warming scenarios Flooding is most effective early in the sea ice growth season and is not beneficial in summer The combination of reduced greenhouse gas emissions and increased flooding is most successful at reducing Arctic sea ice loss