There has been a recurring sensible heat polynya located in the west Cosmonaut Sea, which was first discovered by satellite in the 1970s and was named the western Cosmonaut Sea Polynya (wCSP). wCSP forms periodically in late autumn and early winter in the Southern Hemisphere, which usually takes about half a month from the initiation to the complete closure. The Southern Ocean Sate Estimate (SOSE) reanalysis product is employed to investigate the thermodynamic and dynamic factors controlling the formation of the wCSP in 2009, when the polynya area revealed from satellite observations are seasonally simulated by SOSE. Oceanic heat budget analysis for the surface layer above the thermocline reveals that the heat advection is the major term contributing to the surface heat content variation in the wCSP. The precursor of wCSP—the embayment is formed during the passage of a cyclone. The negative wind stress curl from the cyclone induces upwelling of warm circumpolar deep water to the surface, and meanwhile enhances the meridional heat transport into the polynya region by enhancing the contrast in meridional velocities across the northern and southern boundaries of the polynya area. Both of the vertical heat advection and the meridional heat advection contribute significantly to increased heat content in the surface layer of wCSP and caused sea ice melting, forming the embayment. At the same time, the cyclonic wind field also promotes convergence of sea ice over northern area of the embayment and results in an enclosed polynya.
 

west Cosmonaut Sea Polynya,heat budget,dynamics,cyclonic wind field