Could the Last Interglacial Constrain Projections of Future Antarctic Ice Mass Loss and Sea‐Level Rise?

Abstract

Previous studies have interpreted Last Interglacial (LIG; ∼129-116 ka) sea-level estimates in multiple different ways to calibrate projections of future Antarctic ice-sheet (AIS) mass loss and associated sea-level rise. This study systematically explores the extent to which LIG constraints could inform future Antarctic contributions to sea-level rise. We develop 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. We use a Bayesian approach conditioning emulator projections on a set of LIG constraints to find associated likelihoods of model parameterizations. LIG estimates inform both the probability of past and future ice-sheet instabilities and projections of future sea-level rise through 2150. Although best-available LIG estimates do not meaningfully constrain Antarctic mass loss projections or physical processes until 2060, they become increasingly informative over the next 130 years. Uncertainties of up to 50 cm remain in future projections even if LIG Antarctic mass loss is precisely known (±5 cm), indicating that there is a limit to how informative the LIG could be for ice-sheet model future projections. The efficacy of LIG constraints on Antarctic mass loss 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.

Rapid postglacial rebound amplifies global sea level rise following West Antarctic Ice Sheet collapse

“…This estimate is commonly cited as the maximum contribution of WAIS to peak GMSL during the last interglacial (LIG; ~130 to 116 ka) (19)(20)(21)(22)(23). A total Antarctic contribution to the LIG higher than this would thus imply melt from the East Antarctic Ice Sheet (EAIS) (24)(25)(26). Furthermore, when combined with independent estimates of GMSL changes associated with the Greenland Ice Sheet (18,24,(27)(28)(29), mountain glaciers (30), and thermal expansion (31), the estimate of 3.26 m has led to the view that the lower bound on a widely cited estimate of peak GMSL during the LIG [5.5 to 9 m; (19,32)] requires no contribution from the EAIS, while it is likely that the upper bound does (33).…”

The Transient Sea Level Response to External Forcing in CMIP6 Models

“…Here paleo records, rather than historical records, can serve as an important constraint for models. We note that a credible equilibrium response does not guarantee a credible transient sensitivity as the equilibrium can be approached at different speeds (Gilford et al., 2020 ). Finally, we associate about 90% of SLR since the start of the twentieth century with anthropogenic global warming.…”

An iterative process for efficient optimisation of parameters in geoscientific models: a demonstration using the Parallel Ice Sheet Model (PISM) version 0.7.3

“…The lateral boundaries of the ice sheet are free to evolve (Winkelmann et al, 2011). Subgrid parameterisations are used to describe the positions of the ice shelf calving fronts (Albrecht et al, 2011) and the grounding lines (Gladstone et al, 2010;Feldmann et al, 2014). Calving is described using the physically based two-dimensional parameterisation of Levermann et al (2012).…”