The ANDREX project seeks to assess the role of the Weddell gyre in driving the southern closure of the meridional overturning circulation, in ventilating the deep global ocean, and in sequestering carbon and nutrients in the global ocean abyss.

To do this, the ANDREX team, a group of German collaborators and a group of US collaborators set out to obtain measurements of hydrography, velocity and a range of ventilation tracers and biogeochemical substances along the Weddell gyre’s rim. These measurements were organized into three surveys: a US CLIVAR section (a WOCE I6S repeat) between South Africa and Antarctica along 30°E in January–February 2008; the ANDREX section proper along the gyre’s northern edge between 30°E and the tip of the Antarctic Peninsula, in December–February 2009. The ANDREX section was aborted approximately half-way due to a medical evacuation, and was completed in March–April 2010 on board the RRS James Clark Ross. Finally, the box is close by the German Sr04 section (January–April 2005) in the Southwestern Weddell Sea between Kapp Norvegia and the tip of the Antarctic Peninsula.

Track of the ANDREX cruise: the ANDREX line (JR239 + JC30) goes from the tip of the Antarctic Peninsula to 30°E; the CLIVAR I6S section follows 30°E to the Antarctic continent, Sr04 goes from Kapp Norvegia (15°E) to the tip of the Antarctic Peninsula (the bathymetry is shown in greyscale)

Specifically, ANDREX will use a combination of inverse estimation techniques and tracer and biogeochemical analyses to:

  • Quantitatively assess the import / export routes of Circumpolar Deep Water / Antarctic Bottom Water (AABW) to / from the Weddell gyre.
  • Obtain an optimal, self-consistent estimate of the rates of ventilation and AABW formation in the Weddell gyre.
  • Quantify the heat and freshwater budgets of the Weddell gyre, and determine the freshwater inputs to the gyre (sea ice melt, precipitation, and glacial ice).
  • Quantify the nutrient and carbon cycles of the Weddell gyre.
  • Determine the rate of sequestration of anthropogenic carbon into the deep Weddell gyre.
  • Investigate the extent to which ventilation in, and AABW export from, the Weddell gyre have varied on interannual to decadal time scales.

Schematic of the circulation in the Weddell Sea (in black). The red arrows represent the escape route from the Weddell Sea. The white arrows are the eastern branches of the Weddell Gyre

The ANDREX team encompasses scientists from four UK institutions: the National Oceanography Centre, Southampton (NOC), the British Antarctic Survey (BAS), the University of East Anglia (UEA), and the University of Manchester; one German institution: the Alfred-Wegener-Institut, Bremerhaven; and one US institution: the Woods Hole Oceanographic Institution. Alberto Naveira Garabato is the project's Principal Investigator. ANDREX is funded by the UK's Antarctic Funding Initiative (AFI).