Bottom water formation and polynyas in Adelie Land, Antarctica

Antarctic Bottom Water is the coldest and densest water found in the global ocean. It spreads into all the major ocean basins, carrying the cold water towards the equatorial regions, and is a central component of the global thermo-haline circulation. However, the mechanisms of bottom water formation are not well established; its geographical distribution and rate of formation have yet to be fully quantified. Polynyas, which are large persistent openings in sea-ice that form during the winter near the Antarctic Coast, playa central role in the formation or Antarctic Bottom Water. This paper describes the bottom water formation around the Antarctic continental margin with particular emphasis on the processes and mechanisms of the Adelie Land Bottom Water formation near Dumont D'Urville south of Tasmania

Interactions between Antarctic sea ice and large-scale atmospheric modes in CMIP5 models

The response of Antarctic sea ice to large-scale patterns of atmospheric variability varies according to sea ice sector and season. In this study, interannual atmosphere–sea ice interactions were explored using observations and reanalysis data, and compared with simulated interactions by models in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Simulated relationships between atmospheric variability and sea ice variability generally reproduced the observed relationships, though more closely during the season of sea ice advance than the season of sea ice retreat. Atmospheric influence on sea ice is known to be strongest during advance, and it appears that models are able to capture the dominance of the atmosphere during advance. Simulations of ocean–atmosphere–sea ice interactions during retreat, however, require further investigation. A large proportion of model ensemble members overestimated the relative importance of the Southern Annular Mode (SAM) compared with other modes of high southern latitude climate, while the influence of tropical forcing was underestimated. This result emerged particularly strongly during the season of sea ice retreat. The zonal patterns of the SAM in many models and its exaggerated influence on sea ice overwhelm the comparatively underestimated meridional influence, suggesting that simulated sea ice variability would become more zonally symmetric as a result. Across the seasons of sea ice advance and retreat, three of the five sectors did not reveal a strong relationship with a pattern of large-scale atmospheric variability in one or both seasons, indicating that sea ice in these sectors may be influenced more strongly by atmospheric variability unexplained by the major atmospheric modes, or by heat exchange in the ocean