Sea Ice Historical Forecast Project (Ice-HFP)

Tremendous advance in improving and exploiting the initialization of the oceanic and atmospheric components of seasonal forecast systems has been made in the past decade, particularly with the advent of enhanced knowledge of the world's oceans through ARGO. Utilizing the increased knowledge of sea ice conditions within seasonal prediction systems remains an untapped and unknown reservoir of potential predictability. Current seasonal prediction systems range from prescribed sea ice climatologies to fully thermodynamic and dynamic interactive sea ice initialized from an observed state. To gain understanding of the potential impact of sea ice initialization on the atmosphere, it is necessary to perform model comparisons with and without sea ice initialization. There have been suggestions that winter pre-conditioning and anomalous spring sea ice extent could influence Northern Hemisphere circulation. Effects on the location of the summertime North Atlantic Storm Track (Balmeseda et al., 2010) and the winter time circulation (e.g. Francis et al., 2009) have both been suggested. However, it is not yet known if these effects are robust and in particular whether the initialisation of sea-ice can improve predictions of seasonal climate variability. We suggest a concise set of multi-model sensitivity experiments to examine the effects of sea ice initialization in seasonal prediction systems. The experiments are a simple test of initializing sea ice conditions with the observed sea ice state versus initializing with a climatology. All other components of the seasonal prediction system would be initialized identically across the two experiments. As usual, no use of any future information should be allowed in any of the system components. Although the scope of this proposal favours the use of interactive ice models, it should not be seen as excluding simplistic statistical modelling of ice -- for instance the influence of prescribing persisted sea ice anomalies versus prescribing climatology. The primary goal of the study is to demonstrate the influence of proper initialization of sea ice on atmospheric circulation.