initMIP-Antarctica: An ice sheet model initialization experiment of ISMIP6

ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6) is the primary activity within the Coupled Model Intercomparison Project - phase 6 (CMIP6) focusing on the Greenland and Antarctic Ice Sheets. Ice sheet model simulations are influenced by their initial conditions, but the impact of these conditions on simulations of ice sheet evolution over the next couple of centuries remains poorly understood. To better quantify this impact and its associated uncertainties, a first intercomparison exercise (initMIP) has been designed to compare, evaluate and improve initialization procedures and estimate their impact on century time-scale simulations. Following the initMIP-Greenland exercise, the new initMIP-Antarctica has been designed to explore uncertainty associated with model initialization and spin-up and to evaluate initialization procedures. Apart from the initialization procedure itself, which varies from model to model, it consists of a set of three forward experiments of the Antarctic Ice Sheet that are each run for one hundred years: i) a control run (ctrl), ii) a run with prescribed surface mass balance anomaly (asmb) and iii) a run with prescribed basal melt anomaly applied under floating ice (abmb). All other model parameters are the same as those used for the initialization procedure. In this study, we present the results of initMIP-Antarctica performed by different modeling groups and investigate the similarities and differences within these simulations.