Supplementary material to "Benefits and challenges of dynamic sea-ice for weather forecasts"

Abstract. The drive to develop environmental prediction systems that are seamless across both weather and climate timescales has culminated in the development and use of Earth system models, which include a coupled representation of the atmosphere, land, ocean and sea ice, for medium-range weather forecasts. One region where such a coupled Earth system approach has the potential to significantly influence the skill of weather forecasts is in the polar and sub-polar seas, where fluxes of heat, moisture and momentum are strongly influenced by the position of the sea ice edge. In this study we demonstrate that using a dynamically coupled ocean and sea ice model in ECMWF Integrated Forecasting System, results in improved sea ice edge position forecasts in the northern hemisphere in the medium-range. Further, this improves forecasts of boundary layer temperature and humidity downstream of the sea ice edge in some regions during periods of rapid change in the sea ice compared to forecasts in which the sea surface temperature anomalies and sea ice concentration do not evolve throughout the forecasts. Challenges and limitations, such as the quality of ocean and sea ice initial conditions or analyses, and the inability of the coupled system to capture the rate of sea ice concentration change during periods of ice advance and retreat will also be discussed.