Relationship between synoptic forcing and polynya formation in the Cosmonaut Sea: 1. Polynya climatology

A polynya has been observed in satellite imagery to occur irregularly between the months of July and October in the Cosmonaut Sea. To investigate the processes of formation, maintenance, and decay of these polynyas, a 13-year climatology of Antarctic atmospheric and surface conditions is assembled from numerical weather prediction model analyses and remotely sensed satellite observations. An analytical technique used previously to identify and track atmospheric low pressure systems is modified to identify polynyas from daily analyses of sea ice area. This information is used to prepare a set of monthly climatological conditions as well as their anomalies when a polynya is present. Previous studies have suggested a link between atmospheric forcing and polynya formation. Along with the drop in sea ice area, there is a drop in sea level pressure as well as an increase in atmospheric wind divergence when the Cosmonaut Sea polynya is present. In some months, the sea ice area decrease is preceded by the passage of an atmospheric low pressure system 1-2 days earlier, but due to the continuous presence of katabatic winds and the coarseness of the ECMWF data, there is not as definitive a relationship between wind divergence and sea level pressure or ice area. Errors associated with the processing of passive microwave remotely sensed data, as well as differences in spatial scale limit that can be determined about the ocean state from the data sets, suggest the need for improved surface classification techniques, as well as regional modeling studies.