Cost benefit of installing seabed curtains in Pine Island Trough

We explore the costs and benefits in terms of sea level rise avoided by installing seabed curtains designed to limit access of deep water to the glaciers in the Amundsen Sea embayment, West Antarctica. The ocean hydrography and circulation are simulated using a 3-4 km resolution regional ocean model of the Amundsen and Bellingshausen Seas driven by ERA-Interim, which shows good agreement with existing observations over the 1992-2001 period. In this ocean model, ice shelf geometry as well as cavity ocean circulation is resolved, allowing us to calculate ice shelf melting as a function of simulated ocean temperature and speed at the ice shelf base. We impose seabed curtains in the model by a topographic wall with curtain top heights varying between 600 and 300 m below the sea surface at 73S across Pine Island Trough. To drive the ISSM ice dynamics model of the Thwaites basin with a range of climate forcing for circumpolar deep-water temperature, we parametrize melt rates based on the ocean model output as a function of depth. We explore intervention efficacy, date of installation, and sensitivity to warming rates on sea level rise commitment. We find that efficacy is strongly dependent on the curtain height, and hence length and thence cost of a curtain, and rate of deep water warming (which may be sensitive to mitigation policy). Interventions in Pine Island Trough impact Pine Island as well as Thwaites glaciers, and the ice sheet sea level rise commitment is extended accordingly beyond just the simulated Thwaites basin. The costs of sea level rise damage to global coastlines is estimated as 40 billion/year/metre, indirect costs from avoided human migration are more difficult to quantify economically, but expected to be significant in socio-political terms. Hence, delaying sea level rise can have significant benefits even if interventions simply slow rather than prevent ice sheet collapse. Earlier interventions have greater cost benefits than delaying for a century.