Summer hydrography on the shelf off Terre Ade'lie/George V Land based on the ALBION and CEAMARC observations during the IPY

We report on the hydrographic observations collected on the Antarctic continental shelf between 138E and 146E as part of the CEAMARC and ALBION projects in December 2007eJanuary 2008. A total of 140 quasi-synoptic CTD (ConductivityeTemperatureeDepth) casts were analysed to map the spatial distribution of the summer hydrographic properties. Seven distinct hydrographic regimes were identified based on regional topographic features and the presence of specific water masses. These regimes are associated with spatial contrasts in the distribution of the High Salinity Shelf Water (HSSW) and the Modified Circumpolar Deep Water (MCDW). In particular, the HSSW distribution confirms the unique character of Commonwealth Bay in terms of extreme bottom salinity and dissolved oxygen values. The bay appears to be a preferred region for both dense shelf water formation and storage. The systematic survey of the Ade'lie Depression shows the ubiquitous presence of HSSW in the depression, and over the Ade'lie Sill as a 60 m thick layer at the centre of the sill. This water is dense enough to mix down the continental slope and form Antarctic Bottom Water. Upstream of the sill, the HSSW is shown to sit over the topography with indications of recirculation. The D'Urville Trough, another deep basin on the shelf, is filled with warmer and fresher water that is too light to contribute to the formation of AABW. The D'Urville Trough appears to collect MCDW which enters at the shelf break over the Ade'lie Bank and spreads over the northern slope of the trough. Another branch of MCDWenters in the eastern Ade'lie Sill and is found almost everywhere in the Ade'lie Depression with the noticeable exception of the coastal bays. Additional CTD casts collected during the ALBION-2009 experiment in January 2009 suggest that most of the features observed in 2008 in the Ade'lie Depression should be robust on a year-to-year basis although summer 2009 was characterized by fresher dense shelf waters. 2011 Elsevier B.V. and NIPR. All rights reserved.