Sea Ice - Ocean Feedbacks in the Antarctic Shelf Seas

Over the past forty years a small increasing trend in Antarctic sea ice ex tent has been observed that is the sum of stronger, but opposing, regional and highly seasonal trends. The seasonality of the trends implies the role of feedbacks in modulating the observed trends. A highly simplified coupled sea ice-mixed layer model has been developed to investigate the importance of sea ice-ocean feedbacks on the evolution of sea ice in two contrasting regions of the Southern Ocean: the Amundsen Sea, which has warm shelf waters and a diminishing sea ice cover; and the Weddell Sea, which has cold saline shelf waters and an expanding sea ice cover. Modelling studies where we deny the feedback response to surface air perturbations show the importance of feedbacks on the mixed layer and ice cover in the Weddell Sea to be smaller than the sensitivity to surface atmospheric conditions. In the Amundsen Sea the effect of surface air temperature perturbations on the sea ice are opposed by changes in the entrainment of warm deep waters into the mixed layer. The net impact depends on the relative balance between changes in sea ice growth driven by surface perturbations and basal driven melting. The changes in the entrainment of warm water in the Amundsen Sea was found to have a much larger impact on the ice volume than perturbations in the surface energy budget.