Seasonal Forecasts of Ice Extent for the Arctic and Baltic Sea using GloSea5

The Met Office seasonal forecast system GloSea has been producing forecasts of September mean Arctic sea ice extent over the past six years. We will present estimates for the skill of our sea ice forecasts over the 1996-2009 hindcast period that is run as part of the operational GloSea5 system. Although, the major interest is ice extent and ice coverage during the September minimum, we will also show the skill of the system throughout the whole year. In the process, we will provide an assessment of the sea ice analysis, which is part of the FOAM/GloSea5 ocean and sea-ice (re)-analysis used as the initial conditions for the forecast/hindcast.

Finally, I will also show skill estimates for determining maximum ice extent in the Baltic Sea in winter. Here biases in the coupled model system, which was not optimally designed for used in a shallow sea such as the Baltic, are such that direct estimates of sea ice cover from the model are not particularly useful. However, using the success of the GloSea5 system for prediction of the large scale circulation, most notably its skillful prediction of the North Atlantic Oscillation (NAO), we have been able to produce accurate predictions of Baltic Sea maximum ice extent, which is strongly dependent on the weather patterns associated with the strength of the NAO.