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 projected to be the largest individual source of future sea level rise and
may have already entered MISI. Here, we use a suite of coupled quasi-2-D
ice–ocean simulations to explore whether targeted geoengineering using
either a continuous artificial sill or isolated artificial pinning points
could counter a collapse. Successful interventions occur when the floating
ice shelf regrounds on the structure, increasing buttressing and reducing ice
flux across the grounding line. Regrounding is more likely with a 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 only has 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 is 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 need to develop contingency plans to deal with an ice
sheet collapse.