Stopping the Flood: Could We Use Targeted Geoengineering to Mitigate Sea Level Rise?

Abstract

Abstract. The Marine Ice Sheet Instability (MISI) is a dynamic feedback that can cause an ice sheet to enter a runaway collapse.Thwaites Glacier, West Antarctica, is the largest individual source of future sea level rise and may have already entered the MISI. Here, we use a suite of coupled ice-ocean flowband simulations to explore whether targeted geoengineering using an artificial sill or artificial ice rises could counter a collapse. Successful interventions occur when the floating ice shelf regrounds on the pinning points, increasing buttressing and reducing ice flux across the grounding line. Regrounding is more likely with a 5 continuous sill that is able to block warm water transport to the grounding line. The smallest design we consider is comparable in scale to existing civil engineering projects but has only a 30% success rate, while larger designs are more effective. There are multiple possible routes forward to improve upon the designs that we considered, and with decades or more to research designs it is plausible that the scientific community could come up with a plan that was both effective and achievable. While reducing emissions remains the short-term priority for minimizing the effects of climate change, in the long run humanity may 10 need to develop contingency plans to deal with an ice sheet collapse.

18 Politically relevant solar geoengineering scenarios

“…Due to the accelerating rise in sea levels, coastal ecosystems (such as marshes and mangroves) could be lost, exacerbating climate damages. Thus, humanity's primary goal in deploying SRM may not be stabilizing temperatures but holding back the sea (Irvine et al, 2012;Zhao et al, 2017;Wolovick & Moore, 2018;Li et al, 2020;Lockley et al, 2020).…”

Response to Reviewer 1

“…In fact, observations suggest that recent increases in the temperature of water around Antarctica may have already triggered a process that will lead to the collapse of the Pine Island and Thwaites glaciers (Favier et al, 2014;Joughin et al, 2014). Unless an ice stream has exceptionally strong lateral buttressing (Robel et al, 2016), a marine ice sheet instability, once started, may only be stopped by modifying bathymetry to provide extra buttressing, as simulated by flow-band modeling on Thwaites Glacier (Wolovick and Moore, 2018). However, initial results from the BISICLES model evaluating the response of an idealized vulnerable marine glacier to imposed warming found that returning the entire water column to cooler conditions reversed the retreat that had begun during the warming (Asay-Davis et al, 2016).…”

Brief communication: Understanding solar geoengineering's potential to limit sea level rise requires attention from cryosphere experts

“…In fact, observations suggest that recent increases in the temperature of water around Antarctica may have already triggered a process that will lead to the collapse of the Pine Island and Thwaites glaciers (Favier et al, 2014;Joughin et al, 2014). Unless an ice stream has exceptionally strong lateral buttressing (Robel et al, 2016), a marine ice sheet instability, once started, may only be stopped by modifying bathymetry to provide extra buttressing, as simulated by flow-band modeling on Thwaites Glacier (Wolovick and Moore, 2018). However, initial results from the BISICLES model evaluating the response of an idealized vulnerable marine glacier to imposed warming found that returning the entire water column to cooler conditions reversed the retreat that had begun during the warming (Asay-Davis et al, 2016).…”