As stated in the latest assessment report of the IPCC, the future dynamic contribution of the Antarctic Ice Sheet still constitutes one of the main sources of uncertainty in future sea-level projections. By the end of this century, projected ice-sheet changes are limited, with current estimates ranging from a slight mass gain to a mass loss up to tens of centimetres of sea-level equivalent. Sea level could, however, rise for centuries to millennia to come – as sea-level commitment – due to ice-sheet inertia and potentially irreversible large-scale ice loss from Antarctica, which has already been triggered or may be triggered by warming in the next decades or centuries.
In this new study, we systematically study the multi-millennial committed sea-level contribution from the Antarctic Ice Sheet in response to the warming that is projected by climate models at different points in time over the next centuries under lower (SSP1-2.6) and higher (SSP5-8.5) emission pathways.
We find that the West Antarctic Ice Sheet may be committed to a strong grounding line retreat already under the lower emission scenario up to a long-term collapse triggered in 2100 at the latest for the higher emission scenario, raising sea level by multiple meters over the next millennia (see Figure, I and II).
With progressing warming after 2100 that is projected under the higher emission pathway, additional long-term ice loss in East Antarctica follows in our simulations (see Figure, III). For extreme warming projected by some climate models after the year 2200, the ice sheet could decline substantially over the next millennia with a committed sea-level contribution of up to +40 meters (see Figure, IV). This is subject to substantial uncertainties, especially due to the climate models used.
Compared to the sea-level change projected over the next decades, the committed Antarctic sea-level contribution is substantially higher. Our study thus shows the importance of including the sea-level commitment in addition to decadal-to-centennial sea-level projections in, for example, coastal adaptation planning.
Reference: Klose, A. K., Coulon, V., Pattyn, F., and Winkelmann, R.: The long-term sea-level commitment from Antarctica, The Cryosphere, 18, 4463–4492, https://doi.org/10.5194/tc-18-4463-2024, 2024.
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