Adaptation and implementation of the coupled Regional Ocean Modelling System (ROMS) and the Los Alamos sea ice model (CICE) for Baltic Sea

The Regional Ocean Modelling System (ROMS) coupled via Model Coupling Toolkit (MCT) with the Los Alamos sea ice model (CICE) is being prepared. The years 2016-2019 were successfully simulated on a 2.3 x 2.3 km grid with 30 sigma levels and atmospheric forcing delivered externally from data produced by Weather Research and Forecast Model (WRF). For long-term hindcast simulations it is assumed to use the other sources of atmospheric data such as reanalysis.

The latest work was focused on the creation of a new high resolution grid. Bathymetry with a resolution of 500 m was used, which was then filtered to meet the slope factor and so-called Haney number criteria. In this way, a grid with 40 sigma layers and a 2700x3200 horizontal number of nodes (which corresponds to a resolution of 0.25 NM) was created. In addition, interpolation of forcing data was introduced to save disk space. Relevant pieces of code have been added to both ROMS and CICE that made possibility of delivering atmospheric data on 600x640 grid which is almost 23 times smaller than model grid.

In the future it is planned to work on the CICE model for improving its compatibility with satellite data. In particular, it will be interesting to compare the ice deformations available from the model output with those calculated from consecutive satellite images. Another important aspect of the CICE model appears to have the correct fast ice representation in simulations. In the case of the Baltic Sea, a particularly important area for this phenomenon is the Bay of Bothnia. Preliminary simulations show that CICE underestimates the area covered by fast ice and thus the problem need to be better studied.

Calculations were carried out at the Academic Computer Centre in Gdańsk.