ACCESS-OM: the ocean and sea-ice core of the ACCESS coupled model

The Australian Community Climate and Earth System Simulator Ocean Model (ACCESS-OM), a global coupled ocean and sea-ice model, has been developed at the Centre for Australian Weather and Climate Research1. It is aimed to serve the Australian climate sciences community, including the Bureau of Meteorology, CSIRO2 and Australian universities, for ocean climate research. ACCESS-OM comprises the NOAA/GFDL(3) Modular Ocean Model version 4p1; the LANL(4) Seaice Model version 4.1, a data atmospheric model; and the CERFACS5 OASIS3.25 coupler, which constrains data exchange between the sub-models. ACCESS-OM has been functioning as the ocean and sea-ice coupling core of the ACCESS coupled model, one of the Australian models participating in the Coupled Model Inter-comparison Project phase 5. This paper describes the ACCESS-OM sub-models, coupler, coupling strategy and framework. A selection of key metrics from an ACCESS-OM benchmark simulation, which has run for 500 years using the Coordinated Ocean-ice Reference Experiments normal year forcing, is presented and compared with observations to evaluate the model performance. It shows ACCESS-OM simulates the global ocean and sea-ice climate generally comparably to the results from other ocean sea-ice models of the same class (Griffies et al. 2009). For example, the global ocean volume-averaged temperature undergoes minor evolution. The maximum transport of North Atlantic overturning circulation is 18.5 Sv and the Antarctic Circumpolar Current transport through Drake Passage is 150 Sv, both in fair agreement with the observations; and the sea-ice coverage has reasonable distribution and annual cycle. Measured against other ocean sea-ice models and observations, ACCESS-OM is an appropriate tool for Australia's future ocean climate modelling efforts.