Eos Trans.AGU, 87(52) Fall Meet. Suppl., Abstract OS21C-1611
Mixing Analysis of the Waters in the Shackleton Fracture Zone and the Ona Basin
Frants, M.
The Shackleton Transverse Ridge in the Shackleton Fracture Zone (SFZ) in the Southern Drake
Passage marks a sharp stable chlorophyll front, with chlorophyll levels being much higher in the
Ona Basin to the east of the ridge. Iron fertilization experiments in the Southern Ocean have
indicated that biological productivity is iron-limited. The SFZ is also a region of high mixing,
where the warmer, fresher water of the Antarctic Circumpolar Current mixes with colder, saltier
shelf waters of the South Shetland Islands, the Antarctic Peninsula and the Weddell Sea. The
spreading of the shelf waters northward along the Ridge may transport iron to the Ona Basin,
resulting in higher levels of chlorophyll east of the Ridge. Two cruises, in austral summer 2004
and austral winter 2006, have collected temperature, salinity, oxygen and nutrient data in the
SFZ. The data from both cruises are analyzed using Optimal Multiparameter (OMP) analysis to
determine quantitatively the contributions of individual water masses to the mixing, and
therefore to the iron fertilization process.