The distribution of dissolved zinc (Zn) was investigated in the Atlantic sector of the Southern Ocean in the austral autumn of 2008 as part of the IPY GEOTRACES expedition ZERO & DRAKE. Research focused on transects across the major frontal systems along the Zero Meridian and across the Drake Passage. There was a strong gradient in surface zinc concentrations observed across the Antarctic Polar Front along both transects and high zinc levels were found in surface waters throughout the Southern Ocean. Vertical profiles for dissolved Zinc showed the presence of local minima and maxima in the upper 200 m consistent with significant uptake by phytoplankton and release by zooplankton grazing, respectively. Highest deep water zinc concentrations were found in the centre of the Weddell Gyre associated with Central Intermediate Water (CIW), a water mass which is depleted in O2, elevated in CO2 and is regionally a CFC minimum. Our data suggests that the remineralization of sinking particles is a key control on the distribution of Zn in the Southern Ocean. Disappearance ratios of zinc to phosphate (Zn:P) in the upper water column increased southwards along both transects and based on laboratory studies they suggest slower growth rates of phytoplankton due to iron or light limitation. Zinc and silicate were strongly correlated throughout the study region but the disappearance ratio (Zn:Si) was relatively uniform overall except for the region close to the ice edge on the Zero Meridian.

Sample Collection and Storage Samples were collected during the IPY GEOTRACES Polarstern cruise ANT-XXIV/3 along the Zero Meridian, in the Weddell Sea and Drake Passage between February and April 2008. All samples reported here were collected using the TITAN trace metal clean rosette belonging to the NIOZ (de Baar et al., 2008, doi:10.1016/j.marchem.2007.07.009). Upon recovery of the rosette the complete rosette was carefully moved into a Class 100 clean room container specially built for sampling from this system. Care and maintenance of the GO-FLO bottles was performed by NIOZ technicians using the IPY-GEOTRACES protocols. In the sampling clean room, filtered water samples were collected using slight N2 overpressure and filtration through 0.2 um filter cartridges (Sartorius) from the relevant GO-FLO into 1 L acid-cleaned low density polyethylene bottles for later analysis (acidified onboard with Q-HCl, 1mL/L) in the laboratory in Kiel. Determination of total dissolved Zinc Samples were analyzed in the laboratory by graphite furnace atomic absorption (ETAAS: Perkin-Elmer Model 4100 ZL) after pre-concentration by simultaneous dithiocarbamate-freon extraction, from seawater (100-250 g) (Danielsson et al., 1978, doi:10.1016/S0003-2670(01)83237-2; Grasshoff et al., 1999; Kremling and Streu, 2001, doi:10.1016/S0967-0637(01)00036-X). The accuracy of the analytical procedure was evaluated by measurement of the certified seawater standard NASS-5 (National Research Council of Canada), and the SAFe intercalibration samples S and D2, details of these analyses are found below.

Supplement to: Croot, Peter L; Baars, Oliver; Streu, Peter (2011): The distribution of dissolved zinc in the Atlantic sector of the Southern Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 58(25-26), 2707-2719