Substantial future ice shelf melting projected in West Antarctica regardless of fossil fuel scenario

Mass loss from the West Antarctic Ice Sheet, driven by interactions with the ocean causing melting of ice shelves, is currently Antarctica’s largest contribution to sea level rise. It is not well known how ice shelf melting may evolve in the future, and to what degree this response can be tempered by climate change mitigation. Here we present the most comprehensive future projections of the Amundsen Sea region to date: nearly 4000 years of ice-ocean simulations considering different fossil fuel scenarios and pathways of internal climate variability. All scenarios exhibit significant and widespread future warming of the Amundsen Sea ocean and increased melting of its ice shelves. Even under the most ambitious scenario, where global warming is limited to 1.5°C, the Amundsen Sea warms three times faster than in the historical period. The warming is driven by an increase in onshore transport of warm Circumpolar Deep Water, causing the present-day oscillations between warm and cold periods to converge towards a state of permanent warmth. Until the 2070s, all scenarios are statistically indistinguishable in terms of Amundsen Sea warming; after that, it is only the extreme RCP 8.5 scenario which diverges from the others. Furthermore, the additional ice shelf melting in RCP 8.5 is concentrated in regions which are less glaciologically important for sea level rise. These results suggest that climate mitigation has limited power to prevent West Antarctic ice loss, and that a substantial baseline of future sea level rise is already committed.