Deep water formed around the Antarctic continent drives the world ocean circulation. More than 50% of this deep water is formed within only about 10% of the Antarctic circumpolar band: the Weddell Sea. Subtle changes in the circulation of the Weddell Sea can lead to major changes in floating ice-shelves, with critical implications for global sea-level, the production of deep water, the global ocean overturning circulation, and the associated carbon pumps of the Southern Ocean.

WAPITI had two main components:

One (SME975) in which we will remain north of the Sea-ice zone, in the southern Antarctic Circumpolar Current region. This component of the cruise enters within the framework of the long-term monitoring of this ocean section (A23), as part of BAS core program. It will allow us to assess water-mass modification and changes, and in particular, changes and trends in the Antarctic Bottom Water.

The second component of WAPITI (SME986) aims at zooming onto the source region of Antarctic Bottom Water, where potential changes at A23 would originate. In particular, Antarctic Bottom Water are formed by relatively warm current that enters in contact with ice-shelves. We will investigate the processes controlling the on-shore transport of relatively warm water onto the shelf toward the ice-shelves. Specifically we aim at observing the circulation (seasonality, time-scale) and forcing (tide, sea-ice, air-sea) of the circulation on the continental shelf, and make unprecedented measurements of the biological and physical carbon pumps and associated acidification.

Specifically, involved conducting a one repeat meridional hydrographic section (A23) along ~30°W, south of South Georgia, and a set of small hydrographic and biogeochemical sectionsacross the continental shelf break, and across the Filchner Depression on the continental shelf break, as well as mooring deployment and recovery, float deployments, and seals tagging.Combined, this consisted of more 175 CTD stations, 9 mooring deployments, 3 mooring recovery, 5 tagged seals, 13 floats deployed, plus running underway surface ocean/met sensors.