Ocean-driven melting underneath the Antarctic ice shelves is the main driver of ice loss in Antarctica at present and will play a central role in determining the future contribution of the Antarctic ice sheet to sea level rise. The Antarctic ice-ocean focus group (Task E3) will develop a protocol and provide the boundary conditions for ocean-driven melting to ice sheet modelers that employ them for projections of the Antarctic ice sheet, and provide an analysis of the influence of choices made on the resulting projections. Ocean-driven melting in the ISMIP ice sheet model projections is parameterized. The parameterization usually depends on temperature and salinity ocean forcing that is extrapolated from bias-corrected CMIP model output (updated from Jourdain et al., 2020). There is a range of parameterizations that have been developed in recent years (e.g., Jourdain et al., 2020; Lazeroms et al., 2018; Reese et al., 2018; Pelle et al., 2019; Lambert et al., 2023), which employ uncertain parameters. A number of approaches to optimize these parameter values exist (Burgard et al., 2022; Jourdain et al., 2022; Reese et al., 2023), and ISMIP6 revealed that these choices have a major influence on projected melt rates and sea-level rise (Jourdain et al., 2020; Seroussi et al., 2020; Reese et al., 2021; Edwards et al., 2021). We hence suggest developing, conducting and analyzing a Melt parameterization Model Intercomparison Project (MeltMIP) which, analogously to initMIP for the model initialization (Seroussi et al., 2019), tests in idealized experiments for the influence of the choice of melt parameterization and parameter values on projections.
Explore the new methods for Bias correction & extrapolation of CMIP data in ISMIP7
There are several methods available that can be tested using a "perfect-model approach" with EC-Earth3, CESM2 and UKESM-1-0-LL (optionally ad MIROC / MPI)
Develop a tuning protocol for melt parameterisation
Aim to recommended metrics to use during model tuning and test those in intercomparison exercise
The focus group is actively working on several key components for ISMIP7:
Ocean Present-Day Climatology & Historical Period
Bias Correction Methods
Extrapolation Techniques
Melt Parameterization Tuning Protocol
Melt Parameterization Intercomparison Exercise