Can the Last Interglacial Constrain Projections of Future Antarctic Ice
Mass Loss and Sea-level Rise?
Deep uncertainty in future Antarctic ice-sheet mass loss makes it
challenging to produce robust projections of sea-level rise. Previous
studies used peak last interglacial period (LIG;
~129-116 ka) sea-level estimates to calibrate future
projections of Antarctic mass loss. But LIG estimates have various
depictions and interpretations across the literature. To what extent is
the LIG able to inform future Antarctic contributions to sea-level rise?
This study develops a Gaussian process emulator of an ice-sheet model to
produce continuous probabilistic projections of Antarctic sea-level
contributions over the LIG and a future high-emissions scenario. A
Bayesian approach is used to condition emulator projections on a set of
LIG constraints to find associated likelihoods of model
parameterizations. Results show how LIG estimates inform (1) the
mechanisms of past and future ice-sheet instabilities and (2)
projections of future sea level rise through 2150. Best available LIG
estimates do not meaningfully constrain future near-term Antarctic mass
losses or physical processes. However, LIG estimates become more
informative over time, as projections subject to ice-sheet instabilities
become more positively skewed. Considerable uncertainties in future
projections remain even if peak LIG Antarctic ice-sheet retreat is
precisely known, indicating peak LIG changes are an imperfect analog for
future ice-sheet sensitivities to climate warming. The efficacy of LIG
constraints on Antarctic sea-level contributions also depends on
assumptions about the Greenland ice sheet and LIG sea-level chronology.
However, improved field measurements and understanding of LIG sea-levels
still have potential to improve future sea-level projections,
highlighting the importance of continued observational efforts.