One of the complexities in understanding how the arctic will respond to global scale climate variability and change is the role which snow and sea ice play in controlling energy and mass fluxes across the ocean-sea ice-atmosphere (OSA) interface, particularly in the regions of recurrent polynyas. Polynyas are a significant feature of high latitude climates and are the primary focus of the International Arctic Polynya Program (IAPP) of the Arctic Ocean Sciences Board (AOSB). Since polynyas respond to both oceanic and atmospheric forcing, from local to regional scales, they may be sensitive indicators of climate variability and change . The Canadian Arctic Shelf Exchange Study (CASES), through work on the Cape Bathurst Polynya, and the North Open Water (NOW) research network are/were both Canadian led international research networks which examine the relationship between sea ice variability and marine carbon fluxes. In this paper we provide an overview and intercomparison of these two Canadian Arctic Polynyas which operate under, and respond very differently to, climate variability and change.

Results show that the NOW polynya operates as a latent heat polynya in the winter with forcing from both the atmosphere and ocean. In the spring the polynya is dominated by sensible heat input, from an atmospheric rather than oceanic origin. Fall formation of the sea ice may however be related to oceanic sensible heating. The Cape Bathurst polynya is intimately connected to average aerial sea ice concentration (SIC) reduction in the southern Beaufort Sea which is driven by scale dependent atmospheric and oceanic forcing throughout the annual cycle. We speculate that atmospheric forcing drives oceanic upwelling at the shelf slope break and this contributes to early reduction in SIC. Fall formation of sea ice is delayed by surface mixing of a summer warming of the surface layer. This has resulted in a polynya which has begun to change geographic location (eastward migration) and tends towards increased negative SIC anomalies over the past 25 years.