The seasonally-dependent Antarctic sea ice concentration (SIC) budget is well-observed and synthesizes many important air-sea-ice interaction processes. However, it is rarely well simulated in Earth System Models and means to tune the former are not well understood. In this study, we investigate the sensitivity of 18 key NEMO4.0-SI³ (Nucleus for European Modelling of the Ocean coupled with the Sea Ice modelling Integrated Initiative) model parameters on modelled SIC and sea ice volume (SIV) budgets in the Southern Ocean based on a total of 449 model runs and two global sensitivity analysis methods. We found the simulated SIC/SIV budgets are sensitive to ice strength, the thermal conductivity of snow, the number of ice categories, two parameters related to lateral melting, ice-ocean drag coefficient and air-ice drag coefficient. An optimised ice-ocean drag coefficient and air-ice drag coefficient can reduce the root-mean-square error between simulated and observed SIC budget by about 10%. We recommend ten combinations of NEMO4.0-SI³ model parameters that could yield better sea ice extent and SIC budgets than using the standard values.

NEMO4.0-SI3 model, sea ice budget, sensitivity study