Abstract. Ice sheet numerical modeling is an important tool to estimate the dynamic
contribution of the Antarctic ice sheet to sea level rise over the coming
centuries. The influence of initial conditions on ice sheet model
simulations, however, is still unclear. To better understand this influence,
an initial state intercomparison exercise (initMIP) has been developed to
compare, evaluate, and improve initialization procedures and estimate their
impact on century-scale simulations. initMIP is the first set of experiments
of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), which is
the primary Coupled Model Intercomparison Project Phase 6 (CMIP6) activity
focusing on the Greenland and Antarctic ice sheets. Following
initMIP-Greenland, initMIP-Antarctica has been designed to explore
uncertainties associated with model initialization and spin-up and to
evaluate the impact of changes in external forcings. Starting from the state
of the Antarctic ice sheet at the end of the initialization procedure, three
forward experiments are each run for 100 years: a control run, a run with a
surface mass balance anomaly, and a run with a basal melting anomaly beneath
floating ice. This study presents the results of initMIP-Antarctica from 25
simulations performed by 16 international modeling groups. The submitted
results use different initial conditions and initialization methods, as well
as ice flow model parameters and reference external forcings. We find a good
agreement among model responses to the surface mass balance anomaly but
large variations in responses to the basal melting anomaly. These variations
can be attributed to differences in the extent of ice shelves and their
upstream tributaries, the numerical treatment of grounding line, and the initial ocean conditions applied, suggesting that ongoing efforts to
better represent ice shelves in continental-scale models should continue.
Correction to: Impact of the observed SST frequency in the model initialization on the BSISO prediction
