Climate: Treating multiple sea-ice categories in EC-EARTH

EC-EARTH combines the atmosphere model IFS with the ocean model NEMO with the sea-ice model LIM3 being part of NEMO. An outstanding feature of LIM3 compared to LIM2 which was the sea-ice model in the previous EC-EARTH model version is the ability to represent multiple sea-ice thickness categories. However, this feature can presently not be used to its full extent as IFS only supports a single sea-ice category. To overcome this restriction, the surface scheme of IFS needs some modifications. The exchange between the atmosphere and the underlying surface is already handled in a tiled fashion and therefore new sea-ice tiles can be added in a straightforward way. After including new tiles in IFS, the coupling interfaces of IFS and NEMO need some adjustments to allow the fluxes to be coupled in several sea-ice categories. This work should preferentially be done with NEMO 3.4 or later where the coupling interface already has been prepared for multi category sea-ice, and with a new and more general coupling interface in IFS that is under development.

The planned work covers the technical modifications of the EC-EARTH components to allow the exchange of state variables and fluxes for multiple sea-ice categories, and a first assessment of the impacts on the simulated model climate that follow with multiple sea-ice categories. The technical work will be done in close collaboration with the SeRC application expert on climate model data.