Abstract

A large proportion of Antarctic Bottom Water, the coldest, densest water mass in the World Ocean, originates from Weddell Sea Deep Water (WSDW). For over ten years, BAS has been monitoring the export of WSDW from the Weddell Sea, initially as part of the Long-term Monitoring and Survey programme, and now as part of the NERC cross-centre ORCHESTRA (Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports) programme. We have deployed deep moorings across Orkney Passage, a gap in the South Scotia Ridge that a large proportion of WSDW is exported through, and annually we repeat hydrographic sections along part of the WOCE A23 line, from South Georgia across the Scotia Sea and into the northern Weddell Sea. I will present some results from these measurements, showing recent changes in the properties and volumes of this water mass, and will briefly discuss the possible causes and consequences, of these changes.