Atmospheric forcing of the Cosmonaut Sea polynya

A transient sensible heat polynya has been observed through the passive microwave satellite record in the Cosmonaut Sea off the coast of Cape Ann, Antarctica. Originally, Comiso and Gordon (1996) theorized that this polynya was formed through upwelling caused by the contraction of fluid columns and stretching due to potential vorticity conservation. They suggested that the heat provided from the upwelled circumpolar deep water was sufficient to maintain an ice-free region. Through the use of a regional climate system model, however, we have determined that ice divergence caused by an atmospheric divergence produces a polynya in the model with a similar frequency to the observed polynya. The atmospheric divergence is related to the interaction of the synoptic scale systems and the continental katabatic winds. We have also determined that a specified 'bull's-eye' oceanic heat flux of 200 W/m2 is insufficient to form and maintain a polynya in the model. Additionally, through model diagnostics, the formation is consistent with the sensible heat polynya concept as opposed to latent heat polynyas which are also present in the simulations. A correlation of the the large-scale atmospheric analyses with the available satellite data in the region demonstrates a link between the atmosphere and the polynya formation. Thus, the true polynya is speculated to form through atmospheric divergence which drives the sea ice and ocean divergence and hence the oceanic upwelling which maintains the polynya. This idea suggests that the Cosmonaut Sea polynya is a wind-driven sensible heat polynya.